**3. Benefits of unilateral cochlear implants**

## **3.1 Environmental awareness**

At the most basic level, cochlear implants provide children with an auditory awareness of their environment. Through their cochlear implant, children can hear many environmental

Cochlear Implants in Children: A Review 339

the ability to label sounds, letters or words (Spencer et al., 2011). With the introduction of earlier diagnosis of hearing loss through newborn hearing screening, a need to assess very young children has developed in order to determine their suitability for cochlear implants. There are several methods of doing this, but these are less objective, and are much more reliant on the expertise and judgement of professionals in observing behavioural responses in very young children, and also on parent reports of responses to speech sounds and specific familiar words. Reports using these modified forms of speech perception testing in very young children have suggested that speech perception skills can develop rapidly within the first two years of cochlear implantation for children implanted before 4 years of

age (Robbins et al., 2004a; Svirsky et al., 2004; Tajudeen et al., 2010; Wie et al., 2007).

th' etc.).

As previously mentioned, much of the improvement in speech perception scores is attributable to advancements in technology, and particularly to the development of more effective speech processing strategies for the three commercially available cochlear implant devices (the Nucleus/Cochlear device, the Clarion device, and the Med-El device). The development of speech processing technology in the Cochlear device, which retains a dominant international market share of around 70% (Patrick et al., 2006) will be discussed as an example of this progress. In the early Nucleus 22-channel cochlear implant device, speech feature extraction schemes that presented only the fundamental frequency of speech and the first two formants (or bursts of energy) of speech (F0F2 and F0F1F2) were used (Clark et al., 1983). These strategies provided an aid to lip reading and very limited speech perception ability (Dowell et al., 1985). They had several disadvantages, such as not discriminating between speech and non-speech sounds, causing some environmental noises to sound quite unnatural, and providing no information above 3kHz, which made it impossible for users to perceive unvoiced information about consonants (such as 's', 'sh', 'f','

In the early 1990's, a new strategy, known as Multipeak (MPEAK), was introduced with the goal of improving consonant recognition scores. MPEAK still used feature extraction algorithms, but also provided information about high frequency sounds on three fixed bands of the implant electrode array. The MPEAK strategy represented an improvement in that it distinguished between voiced and unvoiced sounds, and some electrodes were allocated to the representation of high frequency consonant information, which is extremely important for speech perception. The additional information provided through this speech processing strategy led to improved speech perception scores, particularly for fricatives (eg. 's', 'sh'), in both quiet and noise conditions (Clark, 1989; Dowell et al., 1991). Despite the improvements in benefit with MPEAK, an ongoing disadvantage of formant extraction

By 1995, improvements in electronics technology had allowed a new approach to speech processing to be adopted, using bandpass filtering principles in order to provide more information about the speech spectrum. The Spectral (SPEAK) speech processing strategy used bandpass filters to select 6 to 10 of the largest spectral components in each analysis time period and assigned these to particular electrodes in the cochlea. In this strategy, groups of electrodes, rather than single electrodes, were stimulated to represent particular speech features such as vowels, and stimulation occurred at a much higher rate than for previous strategies, which meant that more information could be presented more quickly. The selection of the highest amplitude information increased the chance of presenting only

strategies was that in background noise the speech processor made errors.

sounds that would not be audible to them through hearing aids. These include high frequency sounds such as water running, birds singing, the kettle whistling, the car indicators ticking and the phone ringing. Being able to hear what is going on in their environment gives children a feeling of connectedness with the world, and also provides them with a greater degree of safety, although localization of sound sources is usually not achieved by most children with only one cochlear implant. Children are more easily able to hear their name being called, to determine when someone is speaking to them, and even to enjoy music. In the early days of cochlear implantation, when only older children received implants, and before it was realised that children could use cochlear implants to develop spoken language, environmental awareness was a prime motivating factor in the decision to implant some children (Sarant et al., 1994).

#### **3.2 Speech perception**

The cochlear implant assists children to process spoken auditory information in their environment both as an aid to lip reading, which is particularly useful in noisy educational environments, and also as a source of auditory information that can be relied upon without lip reading in appropriate listening conditions. As briefly mentioned earlier, speech perception results for children have steadily improved over time with advances in device hardware and software, surgical techniques, and experience with programming speech processors and habilitation. Initially, it was not expected that children with congenital hearing loss would be able to achieve the speech perception abilities shown by postlingually deafened adults, but many children have exceeded these levels of perceptual ability. By the mid 1990's, 60 to 80% of children with unilateral implants achieved open-set word and sentence speech perception abilities comparable to those achieved by adults using audition only (Dowell et al., 1995; Dowell et al., 1997; Geers et al., 2003; Sarant et al., 2001).

More recent studies of children implanted at younger ages and using more recent technologies report even better speech perception abilities. While it has been suggested for some time that children with cochlear implants perform at a level equivalent to that of a child with a severe hearing loss using hearing aids (Blamey et al., 2001a; Boothroyd, 1997; Svirsky & Meyer, 1999), it has recently been reported that very young children can perform on tests of speech recognition at a level equivalent to that of children with a moderate hearing loss using hearing aids (Leigh et al., 2008b). Recent long-term studies have also shown that high proportions of children (79% and 60%) can use the telephone (Beadle et al., 2005; Uziel et al., 2007). These are considerable achievements for children who have been profoundly deaf since birth, and who have developed their auditory processing abilities through the reduced and fragmented sound provided by cochlear implants. It is also worth noting that a meta-analysis of 1916 reports on speech perception performance in children with cochlear implants suggested that, rather than levelling out, speech perception benefits continue to increase as children grow older (Cheng et al., 1999).

The assessment of speech perception abilities in adults and older children is relatively straightforward. It may involve an individual listening to a sound or word and pointing to a picture that best represents that sound or word (closed-set testing) or could involve the individual listening to and repeating a sound, word or sentence spoken by the assessor with no context (open-set testing). Children with age-appropriate cognitive abilities are able to complete these sorts of tasks from the age of around 3 to 4 years, when they have developed

sounds that would not be audible to them through hearing aids. These include high frequency sounds such as water running, birds singing, the kettle whistling, the car indicators ticking and the phone ringing. Being able to hear what is going on in their environment gives children a feeling of connectedness with the world, and also provides them with a greater degree of safety, although localization of sound sources is usually not achieved by most children with only one cochlear implant. Children are more easily able to hear their name being called, to determine when someone is speaking to them, and even to enjoy music. In the early days of cochlear implantation, when only older children received implants, and before it was realised that children could use cochlear implants to develop spoken language, environmental awareness was a prime motivating factor in the decision to

The cochlear implant assists children to process spoken auditory information in their environment both as an aid to lip reading, which is particularly useful in noisy educational environments, and also as a source of auditory information that can be relied upon without lip reading in appropriate listening conditions. As briefly mentioned earlier, speech perception results for children have steadily improved over time with advances in device hardware and software, surgical techniques, and experience with programming speech processors and habilitation. Initially, it was not expected that children with congenital hearing loss would be able to achieve the speech perception abilities shown by postlingually deafened adults, but many children have exceeded these levels of perceptual ability. By the mid 1990's, 60 to 80% of children with unilateral implants achieved open-set word and sentence speech perception abilities comparable to those achieved by adults using audition only (Dowell et al., 1995; Dowell et al., 1997; Geers et al., 2003; Sarant et al., 2001). More recent studies of children implanted at younger ages and using more recent technologies report even better speech perception abilities. While it has been suggested for some time that children with cochlear implants perform at a level equivalent to that of a child with a severe hearing loss using hearing aids (Blamey et al., 2001a; Boothroyd, 1997; Svirsky & Meyer, 1999), it has recently been reported that very young children can perform on tests of speech recognition at a level equivalent to that of children with a moderate hearing loss using hearing aids (Leigh et al., 2008b). Recent long-term studies have also shown that high proportions of children (79% and 60%) can use the telephone (Beadle et al., 2005; Uziel et al., 2007). These are considerable achievements for children who have been profoundly deaf since birth, and who have developed their auditory processing abilities through the reduced and fragmented sound provided by cochlear implants. It is also worth noting that a meta-analysis of 1916 reports on speech perception performance in children with cochlear implants suggested that, rather than levelling out, speech perception benefits

implant some children (Sarant et al., 1994).

continue to increase as children grow older (Cheng et al., 1999).

The assessment of speech perception abilities in adults and older children is relatively straightforward. It may involve an individual listening to a sound or word and pointing to a picture that best represents that sound or word (closed-set testing) or could involve the individual listening to and repeating a sound, word or sentence spoken by the assessor with no context (open-set testing). Children with age-appropriate cognitive abilities are able to complete these sorts of tasks from the age of around 3 to 4 years, when they have developed

**3.2 Speech perception** 

the ability to label sounds, letters or words (Spencer et al., 2011). With the introduction of earlier diagnosis of hearing loss through newborn hearing screening, a need to assess very young children has developed in order to determine their suitability for cochlear implants. There are several methods of doing this, but these are less objective, and are much more reliant on the expertise and judgement of professionals in observing behavioural responses in very young children, and also on parent reports of responses to speech sounds and specific familiar words. Reports using these modified forms of speech perception testing in very young children have suggested that speech perception skills can develop rapidly within the first two years of cochlear implantation for children implanted before 4 years of age (Robbins et al., 2004a; Svirsky et al., 2004; Tajudeen et al., 2010; Wie et al., 2007).

As previously mentioned, much of the improvement in speech perception scores is attributable to advancements in technology, and particularly to the development of more effective speech processing strategies for the three commercially available cochlear implant devices (the Nucleus/Cochlear device, the Clarion device, and the Med-El device). The development of speech processing technology in the Cochlear device, which retains a dominant international market share of around 70% (Patrick et al., 2006) will be discussed as an example of this progress. In the early Nucleus 22-channel cochlear implant device, speech feature extraction schemes that presented only the fundamental frequency of speech and the first two formants (or bursts of energy) of speech (F0F2 and F0F1F2) were used (Clark et al., 1983). These strategies provided an aid to lip reading and very limited speech perception ability (Dowell et al., 1985). They had several disadvantages, such as not discriminating between speech and non-speech sounds, causing some environmental noises to sound quite unnatural, and providing no information above 3kHz, which made it impossible for users to perceive unvoiced information about consonants (such as 's', 'sh', 'f',' th' etc.).

In the early 1990's, a new strategy, known as Multipeak (MPEAK), was introduced with the goal of improving consonant recognition scores. MPEAK still used feature extraction algorithms, but also provided information about high frequency sounds on three fixed bands of the implant electrode array. The MPEAK strategy represented an improvement in that it distinguished between voiced and unvoiced sounds, and some electrodes were allocated to the representation of high frequency consonant information, which is extremely important for speech perception. The additional information provided through this speech processing strategy led to improved speech perception scores, particularly for fricatives (eg. 's', 'sh'), in both quiet and noise conditions (Clark, 1989; Dowell et al., 1991). Despite the improvements in benefit with MPEAK, an ongoing disadvantage of formant extraction strategies was that in background noise the speech processor made errors.

By 1995, improvements in electronics technology had allowed a new approach to speech processing to be adopted, using bandpass filtering principles in order to provide more information about the speech spectrum. The Spectral (SPEAK) speech processing strategy used bandpass filters to select 6 to 10 of the largest spectral components in each analysis time period and assigned these to particular electrodes in the cochlea. In this strategy, groups of electrodes, rather than single electrodes, were stimulated to represent particular speech features such as vowels, and stimulation occurred at a much higher rate than for previous strategies, which meant that more information could be presented more quickly. The selection of the highest amplitude information increased the chance of presenting only

Cochlear Implants in Children: A Review 341

recent technology demonstrate the greatest achievements, with intelligibility ratings of 60- 75% and much higher rates of speech production accuracy reported for children implanted as preschoolers (Ertmer et al., 2007; Flipsen, 2008; Peng et al., 2004; Tobey et al., 2003). More recent reports of children followed for longer post-operative periods of up to ten years have reported speech intelligibility rates of 77%, 90%, and 67% respectively, and suggest that the development of intelligibility does not plateau after a few years, but increases over time with chronological age and increased length of cochlear implant use (Beadle et al., 2005; Blamey et al., 2001c; Chin et al., 2003; Uziel et al., 2007). Beadle and colleagues showed that although 48% of the children in their study had developed connected speech that was intelligible to the average listener after 5 years of cochlear implant use, after 10 years this

It was initially unknown whether children with cochlear implants would follow the same pattern of sound acquisition as their peers with normal hearing, or what their rate of progress would be compared to the former. In children with normal hearing, speech acquisition generally takes between 4 to 7 years (Chin et al., 2003). Studies of consonant and vowel acquisition in children with cochlear implants suggest that, on average, these children demonstrate a pattern of phoneme (or speech sound) acquisition similar to that of children with normal hearing (Ertmer et al., 2007; Serry et al., 1997), although their rate of development is often slower (Blamey et al., 2001b). This has meant that the speech acquisition process has still been incomplete at the age at which children with normal hearing have mastered speech production, but with little or no evidence that a plateau in development has been reached for children implanted between 2 and 5 years of age (Blamey et al., 2001c). Initial investigations of a small number of children implanted before the age of 12 months have yielded conflicting results, with one study reporting that the rate of speech production development for children implanted under the age of 12 months matched that of children with normal hearing (Leigh et al., 2008c), and another finding that children implanted before age 12 months and those implanted between 12-24 months showed no difference in their speech production development (Holt & Svirsky, 2008). Future research will hopefully clarify the critical period during which children should receive cochlear implants in order to facilitate speech production outcomes that are similar to those of

Language development is generally measured using standardised assessments of vocabulary and grammatical knowledge. In the early 1990s, most reports on language were case studies demonstrating changes thought to be associated with cochlear implantation, but knowledge in this area has grown over time, and there is now solid evidence for large numbers of children regarding language outcomes. Initial research concentrated on whether children with cochlear implants developed language more quickly than their peers with hearing aids, or compared development to predictions based on pre-operative language development with hearing aids. One of the earlier studies compared language development in three groups of children with cochlear implants, hearing aids and tactile aids (body-worn aids that provide vibratory or electrical stimulation) over 3 years (Geers & Moog, 1994). On average, the language growth of children with cochlear implants in this study was equal to or exceeded that for the other groups of children, and even approached that of children with hearing aids who had 20dB better hearing. Earlier this decade, children with cochlear

figure had increased to 77% (Beadle et al. 2005).

children with normal hearing.

**3.4 Language development** 

the most salient speech information, and of suppressing lower amplitude background noise. The SPEAK strategy resulted in large increases in speech perception benefit for children and adults, particularly in background noise (Cowan et al., 1995; McKay et al., 1991), and probably contributed to the largest increase in speech perception benefit of all the technological advancements made before or since that time. Other significant technological improvements in cochlear implants over the last decade have included new receiverstimulators, smaller, body-worn and behind-the-ear digital speech processors, and further high-rate speech processing strategies. These have facilitated further improvements in speech perception benefit, particularly in very young children who have had access to all of the recent technology.

One of the most challenging findings of research on speech perception ability in children with cochlear implants is the enormous variation in performance between individuals (Cowan et al., 1997; Pyman et al., 2000; Sarant et al., 2001; Staller et al., 1991). While many reports describe 'average' performance, this concept minimises and perhaps even disguises the fact that while many children do reasonably well, and some do as well as their peers with normal hearing, there are still children who derive very little benefit from their cochlear implant. This variation in outcomes makes it difficult to predict how a particular child will perform after implantation, and therefore to determine which children are suitable for a cochlear implant, particularly when they risk losing useable residual hearing in order to have one. Several factors that have been identified as predictive of post-operative performance will be discussed in section 4 of this chapter.

#### **3.3 Speech production**

The development of speech production has always been a significant problem for children with severe-profound hearing loss, as they do not have the auditory capacity to monitor their own speech or to hear the speech of normal-hearing individuals. For many years, most children using hearing aids with this degree of hearing loss have been rated as unintelligible, or as having very low intelligibility, to adult listeners unfamiliar with the speech of children with hearing loss (Bamford & Saunders, 1992; Gold, 1980; Spencer et al., 2011). Cochlear implants can provide children with auditory information that makes their own speech and that of others audible, so that they can learn from speakers with normal hearing, and self-monitor their own speech production. As with speech perception, children with cochlear implants show a wide range of speech production abilities, with many children performing at a very high level, and others showing low levels of performance (Connor et al., 2006; Spencer & Oleson, 2008; Tobey et al., 2003), but even children implanted at relatively late ages and with only a few years of implant use are generally rated as much more intelligible than their peers with a similar degree of hearing loss using hearing aids (Connor et al., 2006; Flipsen, 2008; Tobey & Hasenstab, 1991; Tye-Murray et al., 1995). Speech production outcomes have improved over time, as a result of longer periods of implant experience and improved hardware and speech processing strategies, although for many children they are still not equivalent to those of children with normal hearing (Chin et al., 2003; Peng et al., 2004).

Speech production skills and speech intelligibility ratings equivalent to those of 'gold' hearing aid users have been reported after less than 3 years of implant use (Blamey et al., 2001b; Svirsky et al., 2000). Children who are implanted at younger ages and use more

the most salient speech information, and of suppressing lower amplitude background noise. The SPEAK strategy resulted in large increases in speech perception benefit for children and adults, particularly in background noise (Cowan et al., 1995; McKay et al., 1991), and probably contributed to the largest increase in speech perception benefit of all the technological advancements made before or since that time. Other significant technological improvements in cochlear implants over the last decade have included new receiverstimulators, smaller, body-worn and behind-the-ear digital speech processors, and further high-rate speech processing strategies. These have facilitated further improvements in speech perception benefit, particularly in very young children who have had access to all of

One of the most challenging findings of research on speech perception ability in children with cochlear implants is the enormous variation in performance between individuals (Cowan et al., 1997; Pyman et al., 2000; Sarant et al., 2001; Staller et al., 1991). While many reports describe 'average' performance, this concept minimises and perhaps even disguises the fact that while many children do reasonably well, and some do as well as their peers with normal hearing, there are still children who derive very little benefit from their cochlear implant. This variation in outcomes makes it difficult to predict how a particular child will perform after implantation, and therefore to determine which children are suitable for a cochlear implant, particularly when they risk losing useable residual hearing in order to have one. Several factors that have been identified as predictive of post-operative

The development of speech production has always been a significant problem for children with severe-profound hearing loss, as they do not have the auditory capacity to monitor their own speech or to hear the speech of normal-hearing individuals. For many years, most children using hearing aids with this degree of hearing loss have been rated as unintelligible, or as having very low intelligibility, to adult listeners unfamiliar with the speech of children with hearing loss (Bamford & Saunders, 1992; Gold, 1980; Spencer et al., 2011). Cochlear implants can provide children with auditory information that makes their own speech and that of others audible, so that they can learn from speakers with normal hearing, and self-monitor their own speech production. As with speech perception, children with cochlear implants show a wide range of speech production abilities, with many children performing at a very high level, and others showing low levels of performance (Connor et al., 2006; Spencer & Oleson, 2008; Tobey et al., 2003), but even children implanted at relatively late ages and with only a few years of implant use are generally rated as much more intelligible than their peers with a similar degree of hearing loss using hearing aids (Connor et al., 2006; Flipsen, 2008; Tobey & Hasenstab, 1991; Tye-Murray et al., 1995). Speech production outcomes have improved over time, as a result of longer periods of implant experience and improved hardware and speech processing strategies, although for many children they are still not equivalent to those of children with normal hearing (Chin et

Speech production skills and speech intelligibility ratings equivalent to those of 'gold' hearing aid users have been reported after less than 3 years of implant use (Blamey et al., 2001b; Svirsky et al., 2000). Children who are implanted at younger ages and use more

performance will be discussed in section 4 of this chapter.

the recent technology.

**3.3 Speech production** 

al., 2003; Peng et al., 2004).

recent technology demonstrate the greatest achievements, with intelligibility ratings of 60- 75% and much higher rates of speech production accuracy reported for children implanted as preschoolers (Ertmer et al., 2007; Flipsen, 2008; Peng et al., 2004; Tobey et al., 2003). More recent reports of children followed for longer post-operative periods of up to ten years have reported speech intelligibility rates of 77%, 90%, and 67% respectively, and suggest that the development of intelligibility does not plateau after a few years, but increases over time with chronological age and increased length of cochlear implant use (Beadle et al., 2005; Blamey et al., 2001c; Chin et al., 2003; Uziel et al., 2007). Beadle and colleagues showed that although 48% of the children in their study had developed connected speech that was intelligible to the average listener after 5 years of cochlear implant use, after 10 years this figure had increased to 77% (Beadle et al. 2005).

It was initially unknown whether children with cochlear implants would follow the same pattern of sound acquisition as their peers with normal hearing, or what their rate of progress would be compared to the former. In children with normal hearing, speech acquisition generally takes between 4 to 7 years (Chin et al., 2003). Studies of consonant and vowel acquisition in children with cochlear implants suggest that, on average, these children demonstrate a pattern of phoneme (or speech sound) acquisition similar to that of children with normal hearing (Ertmer et al., 2007; Serry et al., 1997), although their rate of development is often slower (Blamey et al., 2001b). This has meant that the speech acquisition process has still been incomplete at the age at which children with normal hearing have mastered speech production, but with little or no evidence that a plateau in development has been reached for children implanted between 2 and 5 years of age (Blamey et al., 2001c). Initial investigations of a small number of children implanted before the age of 12 months have yielded conflicting results, with one study reporting that the rate of speech production development for children implanted under the age of 12 months matched that of children with normal hearing (Leigh et al., 2008c), and another finding that children implanted before age 12 months and those implanted between 12-24 months showed no difference in their speech production development (Holt & Svirsky, 2008). Future research will hopefully clarify the critical period during which children should receive cochlear implants in order to facilitate speech production outcomes that are similar to those of children with normal hearing.

#### **3.4 Language development**

Language development is generally measured using standardised assessments of vocabulary and grammatical knowledge. In the early 1990s, most reports on language were case studies demonstrating changes thought to be associated with cochlear implantation, but knowledge in this area has grown over time, and there is now solid evidence for large numbers of children regarding language outcomes. Initial research concentrated on whether children with cochlear implants developed language more quickly than their peers with hearing aids, or compared development to predictions based on pre-operative language development with hearing aids. One of the earlier studies compared language development in three groups of children with cochlear implants, hearing aids and tactile aids (body-worn aids that provide vibratory or electrical stimulation) over 3 years (Geers & Moog, 1994). On average, the language growth of children with cochlear implants in this study was equal to or exceeded that for the other groups of children, and even approached that of children with hearing aids who had 20dB better hearing. Earlier this decade, children with cochlear

Cochlear Implants in Children: A Review 343

speakers of more than three other languages without specific instruction. However, there have long been concerns that language delay in bilingual children is due to simultaneously learning two languages, due to the fact that learning a second language delays the learning process with the first language. It seemed logical that, for children with impaired auditory systems who are facing even greater challenges in language acquisition, learning two languages simultaneously would further delay the acquisition of the first language. More recently, it has been found that delays in vocabulary and slower progress in learning the second language dissipate in the early primary school years, and are likely to be due to the amount of exposure children have to each language (ie. the language that is used the most develops more quickly). It has also been demonstrated that language impairments found in bilingual children are due to individual children's innate capacity to learn language, and are

Despite the significant challenge inherent in mastering one spoken language with a cochlear implant, there is emerging evidence that it is also possible for children with cochlear implants to develop competence in a second spoken language. Robbins et al (2004b) reported on 12 children implanted before age 3 years, who not only demonstrated exceptional proficiency in their first language (almost all children had age-appropriate first language) but also solid progress in their second language over the 2 years during which they were followed. The children who were most proficient in their second language development had parents who spoke the second language at home, had opportunities to use the second language outside home, and had extensive cochlear implant experience. It was noted that, as a group, many of these children were 'ideal' cochlear implant recipients; half had hereditary deafness without additional disabilities, none had less than a full electrode array insertion, all had received intensive auditory-oral therapy prior to and after implantation, and none had meningitis-caused deafness. Two other studies have documented the ability of children with cochlear implants to develop competency in a second language. Of 18 children who received their cochlear implants by the age of 5 years and had a mean usage time of 4.5 years, the majority had achieved age-appropriate receptive and/or expressive language skills in their primary language, although their second language skills were still in the early stages of development (Waltzman et al., 2003). Uziel and colleagues (2007) also documented that some of the children in their study

Children with profound hearing loss, including children with cochlear implants, are at increased risk for adverse life outcomes such as loneliness, poorer quality personal relationships, behaviour problems, drug and alcohol problems, and generally poorer quality of life than their normally hearing peers (Meadow, 1980; Watson et al., 1990). These problems can be attributed to a reduced ability to acquire many of the skills that underpin social functioning due to hearing loss (Marschark, 1993), despite their improved auditory capabilities. It is also important to note, however, that not all children with profound hearing loss and/or cochlear implants develop these problems. The impact of hearing loss on children's social and emotional development is also affected by several factors external to the children themselves, such as parental acceptance of and adaptation to their child's hearing loss, quality of family life, the ability of the family to cope, school and community

not caused by simultaneous language learning (Genesee, 2001).

showed some ability to develop competency in a second language.

**3.5 Social and emotional development** 

implants were reported to be developing at a rate similar to that of children with a severe hearing loss of around 78dbHL (Blamey et al., 2001a), and it is now well established that on average, children with cochlear implants demonstrate significantly faster spoken language development than their peers with similar levels of hearing loss who use hearing aids (Connor et al., 2000; Miyamoto et al., 1999; Svirsky et al., 2000; Tomblin et al., 1999). Given these promising results, the focus changed to comparing the progress of children with cochlear implants to that of their normally-hearing peers.

By the late 1990's, although language outcomes for children with cochlear implants had improved compared to those for children with similar degrees of loss using hearing aids, on average, children with cochlear implants were still demonstrating language growth rates of only 50-60% of the rate of children with normal hearing (Blamey et al., 2001a; Davis & Hind, 1999; Geers, 2002; Ramkalawan & Davis, 1992; Wake et al., 2004). Given the fact that these children were already delayed in their language development by the amount of time it had taken for diagnosis and implantation to occur, this slower rate of growth meant that by the time they were of school age, many children were delayed by at least 1 year, and approximately half had a severe language delay (ie. greater than 2 standard deviations below the mean for children with normal hearing). This rate of progress clearly has severe implications for academic achievement and functional literacy outcomes.

Over the past decade, with a decreasing average age at implantation and improved cochlear implant speech processing technology and hardware, language outcomes have further improved for children with cochlear implants, such that some children now acquire spoken language as do children with mild to moderate hearing loss (Spencer et al., 2011). More recently, several studies have shown that children who have received their cochlear implants at very young ages (and have had several years of experience) can achieve spoken language development at similar rates to children with normal hearing (Connor et al., 2006; Duchesne et al., 2009; Geers, 2006b; Schorr et al., 2008; Svirsky et al., 2004; Tomblin et al., 2005). For example, Dettman et al. 2008 reported that children implanted before the age of 2.5 years showed an average vocabulary development rate of 85% of that of children with normal hearing. This means that the gap between chronological age and language age for these children remains more constant, and for some diminishes instead of growing, as has commonly been reported in the past.

Greater proportions of children are showing age-appropriate development in receptive and expressive vocabulary (50% & 58%; Geers et al., 2009) and receptive and expressive language (47% & 39%; Nicholas & Geers, 2008) than previously. It has also been observed that some children with cochlear implants are even able to learn language more quickly than the average child with normal hearing and therefore 'catch up' some of the delay in language acquisition incurred before they received a cochlear implant, with reports of language development at age-appropriate levels between the ages of 4 and 7 years (Yoshinaga-Itano et al., 2010). As with speech perception and speech production, there is still enormous variation in language skills between individuals and between different populations of children (Spencer et al., 2003), with recent reports still documenting many children with significant language delays (Ching, 2010; Connor et al., 2000; Nikolopoulos et al., 2004; Sarant et al., 2009; Young & Killen, 2002).

The capacity for learning language in children with normal hearing is so great that they are not only able to develop fluency in their native language, but can also become fluent

implants were reported to be developing at a rate similar to that of children with a severe hearing loss of around 78dbHL (Blamey et al., 2001a), and it is now well established that on average, children with cochlear implants demonstrate significantly faster spoken language development than their peers with similar levels of hearing loss who use hearing aids (Connor et al., 2000; Miyamoto et al., 1999; Svirsky et al., 2000; Tomblin et al., 1999). Given these promising results, the focus changed to comparing the progress of children with

By the late 1990's, although language outcomes for children with cochlear implants had improved compared to those for children with similar degrees of loss using hearing aids, on average, children with cochlear implants were still demonstrating language growth rates of only 50-60% of the rate of children with normal hearing (Blamey et al., 2001a; Davis & Hind, 1999; Geers, 2002; Ramkalawan & Davis, 1992; Wake et al., 2004). Given the fact that these children were already delayed in their language development by the amount of time it had taken for diagnosis and implantation to occur, this slower rate of growth meant that by the time they were of school age, many children were delayed by at least 1 year, and approximately half had a severe language delay (ie. greater than 2 standard deviations below the mean for children with normal hearing). This rate of progress clearly has severe

Over the past decade, with a decreasing average age at implantation and improved cochlear implant speech processing technology and hardware, language outcomes have further improved for children with cochlear implants, such that some children now acquire spoken language as do children with mild to moderate hearing loss (Spencer et al., 2011). More recently, several studies have shown that children who have received their cochlear implants at very young ages (and have had several years of experience) can achieve spoken language development at similar rates to children with normal hearing (Connor et al., 2006; Duchesne et al., 2009; Geers, 2006b; Schorr et al., 2008; Svirsky et al., 2004; Tomblin et al., 2005). For example, Dettman et al. 2008 reported that children implanted before the age of 2.5 years showed an average vocabulary development rate of 85% of that of children with normal hearing. This means that the gap between chronological age and language age for these children remains more constant, and for some diminishes instead of growing, as has

Greater proportions of children are showing age-appropriate development in receptive and expressive vocabulary (50% & 58%; Geers et al., 2009) and receptive and expressive language (47% & 39%; Nicholas & Geers, 2008) than previously. It has also been observed that some children with cochlear implants are even able to learn language more quickly than the average child with normal hearing and therefore 'catch up' some of the delay in language acquisition incurred before they received a cochlear implant, with reports of language development at age-appropriate levels between the ages of 4 and 7 years (Yoshinaga-Itano et al., 2010). As with speech perception and speech production, there is still enormous variation in language skills between individuals and between different populations of children (Spencer et al., 2003), with recent reports still documenting many children with significant language delays (Ching, 2010; Connor et al., 2000; Nikolopoulos et

The capacity for learning language in children with normal hearing is so great that they are not only able to develop fluency in their native language, but can also become fluent

cochlear implants to that of their normally-hearing peers.

commonly been reported in the past.

al., 2004; Sarant et al., 2009; Young & Killen, 2002).

implications for academic achievement and functional literacy outcomes.

speakers of more than three other languages without specific instruction. However, there have long been concerns that language delay in bilingual children is due to simultaneously learning two languages, due to the fact that learning a second language delays the learning process with the first language. It seemed logical that, for children with impaired auditory systems who are facing even greater challenges in language acquisition, learning two languages simultaneously would further delay the acquisition of the first language. More recently, it has been found that delays in vocabulary and slower progress in learning the second language dissipate in the early primary school years, and are likely to be due to the amount of exposure children have to each language (ie. the language that is used the most develops more quickly). It has also been demonstrated that language impairments found in bilingual children are due to individual children's innate capacity to learn language, and are not caused by simultaneous language learning (Genesee, 2001).

Despite the significant challenge inherent in mastering one spoken language with a cochlear implant, there is emerging evidence that it is also possible for children with cochlear implants to develop competence in a second spoken language. Robbins et al (2004b) reported on 12 children implanted before age 3 years, who not only demonstrated exceptional proficiency in their first language (almost all children had age-appropriate first language) but also solid progress in their second language over the 2 years during which they were followed. The children who were most proficient in their second language development had parents who spoke the second language at home, had opportunities to use the second language outside home, and had extensive cochlear implant experience. It was noted that, as a group, many of these children were 'ideal' cochlear implant recipients; half had hereditary deafness without additional disabilities, none had less than a full electrode array insertion, all had received intensive auditory-oral therapy prior to and after implantation, and none had meningitis-caused deafness. Two other studies have documented the ability of children with cochlear implants to develop competency in a second language. Of 18 children who received their cochlear implants by the age of 5 years and had a mean usage time of 4.5 years, the majority had achieved age-appropriate receptive and/or expressive language skills in their primary language, although their second language skills were still in the early stages of development (Waltzman et al., 2003). Uziel and colleagues (2007) also documented that some of the children in their study showed some ability to develop competency in a second language.

#### **3.5 Social and emotional development**

Children with profound hearing loss, including children with cochlear implants, are at increased risk for adverse life outcomes such as loneliness, poorer quality personal relationships, behaviour problems, drug and alcohol problems, and generally poorer quality of life than their normally hearing peers (Meadow, 1980; Watson et al., 1990). These problems can be attributed to a reduced ability to acquire many of the skills that underpin social functioning due to hearing loss (Marschark, 1993), despite their improved auditory capabilities. It is also important to note, however, that not all children with profound hearing loss and/or cochlear implants develop these problems. The impact of hearing loss on children's social and emotional development is also affected by several factors external to the children themselves, such as parental acceptance of and adaptation to their child's hearing loss, quality of family life, the ability of the family to cope, school and community

Cochlear Implants in Children: A Review 345

language skills (Dammeyer, 2010; Percy-Smith et al., 2008b). Social development usually follows language skill development, and improvements in both have been observed to occur more quickly for children with cochlear implants than for children with severe-profound hearing loss using hearing aids (Bat-Chava et al., 2005). It has been suggested that improved spoken language and communication skills facilitate psychosocial development through an ability to communicate and a subsequent increase in confidence (Bat-Chava & Deignan, 2001). Children with severe-profound deafness have historically been found to have lower levels of self-esteem than their peers with normal hearing (Nicholas & Geers, 2003), with the self-esteem of adolescents being lower than that of younger children (Schorr, 2006). It has been suggested that unless their language skills match those of their hearing peers, children with cochlear implants cannot fully integrate into the hearing community and develop positive self-esteem (Crouch, 1997; Lane & Grodin, 1997). However, as with many recent outcomes for children with cochlear implants, more recent research has shown equivalent levels of self esteem in children with cochlear implants and children with normal hearing

Recent studies have also used measures of health-related quality of life (QOL) to investigate psychosocial development in children with cochlear implants, using both parental and child reports. QOL is considered to be an assessment of well-being across various areas of life such as social interaction, school adjustment, friendships, communication, and listening ability. Although a potential limitation of QOL measures can be that although parents are well-informed of their children's level of physical functioning, they have a tendency to underestimate their psychosocial functioning (Zaidman-Zait, 2011), QOL assessments are still regarded as a useful method of obtaining a more holistic measure of benefit. Loy and colleagues (2010) found no significant differences between overall reported QOL for children with cochlear implants compared to their peers with normal hearing, in either younger (8-11 years) or older (12-16 years) groups, although the younger group rated QOL more highly than did the adolescent group. Others have reported similar findings for

Several factors have been found to influence psychosocial development in children with cochlear implants. Children who are implanted earlier and therefore have a longer duration of implant use are reported to be more socially competent (Leigh et al., 2008a; Martin et al., 2011), with girls outperforming boys (Martin et al., 2011; Nicholas & Geers, 2003; Percy-Smith et al., 2008b). As mentioned earlier, children implanted at older ages appear to be at greater risk of loneliness (Schorr, 2006), and it has been suggested that this may be due to the fact that they do not develop feelings of belonging and inclusion at a young age, as do children with normal hearing, due to their delayed language prior to implantation. It is also reported that children with cochlear implants in mainstream educational settings who are exposed to spoken, rather than signed, language at home have a higher level of social wellbeing (Percy-Smith et al., 2008b; van Gent et al., 2007). This may be because children in these settings are more likely to have hearing parents, and therefore are continuing to speak their first language in these settings, rather than using sign language at home and spoken language at school, as would children of many deaf parents. There is also no evidence that children with cochlear implants in mainstream educational settings, where speech is used exclusively for communication, have an increased incidence of social or emotional difficulties compared to children in special educational settings (Filipo et al., 1999; Nicholas

(Loy et al., 2010; Martin et al., 2011; Sahli & Belgin, 2006).

children of various ages (Huber, 2005; Warner-Czyz et al., 2009).

& Geers, 2003; Percy-Smith et al., 2008b).

support, and resources (Calderon, 2000; Montanini-Manfredi, 1993). Of course, a child's personality and method of interacting with their social environment also contributes significantly. The few studies that examine the psychosocial development of children with cochlear implants show mixed results (Martin et al., 2011).

It has been reported that children with cochlear implants often have limited pragmatic skills, which can lead to poor social integration (Bat-Chava et al., 2005). Pragmatic skills include using language for different purposes (eg. greeting people, requesting information, demanding information), being able to change language according to the situation or listener (eg. speaking to an adult versus a toddler), and following conversational rules (eg. turn-taking in conversations, using facial expressions and eye contact, rephrasing when misunderstood). Children with poor pragmatic skills may say inappropriate things during conversations, may show little variety in the language they use, or may relate stories in a disorganised, illogical way. These behaviours often lead to a higher incidence of communication breakdown, and can lower social acceptance, as many children may choose to avoid having uncomfortable interactions with others who have pragmatic difficulties. Pragmatic problems are often related to delayed language development, which may include a limited vocabulary, and deficits in knowledge of grammar and age-appropriate slang.

It is not uncommon for children with severe-profound deafness to demonstrate significantly reduced emotional development and social maturity (Bat-Chava et al., 2005; Hintermair, 2006). These children also report loneliness, a lack of close friendships and other psychosocial difficulties more frequently than do their normally-hearing peers (Most, 2007; Stinson & Whitimire, 2000), and some studies show that this is the same for some children with cochlear implants (Boyd et al.,2000; Dammeyer, 2010; Leigh et al., 2009). Older children with cochlear implants (aged 9-14 years) are generally more affected by loneliness than younger children (aged 5-9 years), with children who receive their implants when older being most affected (Schorr, 2006). This may reflect the fact that social interaction becomes increasingly complex in adolescence, and peer group size tends to increase at this time, making communication more difficult due to increased acoustic and social challenges (Bat-Chava & Deignan, 2001; Martin et al., 2011).

Unsurprisingly, loneliness and psychosocial difficulties are greatest for children with additional disabilities, particularly those with low speech intelligibility and poor communication skills, as this increases communication breakdown and results in poorer peer attitudes towards children with these difficulties, who may be rejected or ignored by their peers (Dammeyer, 2010; Hintermair, 2007; Most, 2007; van Gent et al., 2007). Conversely, other studies have found no increased incidence of loneliness and psychosocial difficulties in children with cochlear implants compared to children with normal hearing (Percy-Smith et al., 2008a; Schorr, 2006), and children have been observed by parents to have improved communication skills and social relationships as a result of cochlear implantation (Archbold et al., 2008b; Bat-Chava & Deignan, 2001; Bat-Chava et al., 2005; Huber, 2005; Huttunen & Valimaa, 2010). Children with cochlear implants have been reported to be more likely to be acculturated to hearing society than those with a severe-profound hearing loss using hearing aids (Leigh et al., 2008a).

A statistically significant association has also been found between the level of social wellbeing in children with cochlear implants and their speech perception, production and

support, and resources (Calderon, 2000; Montanini-Manfredi, 1993). Of course, a child's personality and method of interacting with their social environment also contributes significantly. The few studies that examine the psychosocial development of children with

It has been reported that children with cochlear implants often have limited pragmatic skills, which can lead to poor social integration (Bat-Chava et al., 2005). Pragmatic skills include using language for different purposes (eg. greeting people, requesting information, demanding information), being able to change language according to the situation or listener (eg. speaking to an adult versus a toddler), and following conversational rules (eg. turn-taking in conversations, using facial expressions and eye contact, rephrasing when misunderstood). Children with poor pragmatic skills may say inappropriate things during conversations, may show little variety in the language they use, or may relate stories in a disorganised, illogical way. These behaviours often lead to a higher incidence of communication breakdown, and can lower social acceptance, as many children may choose to avoid having uncomfortable interactions with others who have pragmatic difficulties. Pragmatic problems are often related to delayed language development, which may include a limited vocabulary, and deficits in knowledge of grammar and age-appropriate slang.

It is not uncommon for children with severe-profound deafness to demonstrate significantly reduced emotional development and social maturity (Bat-Chava et al., 2005; Hintermair, 2006). These children also report loneliness, a lack of close friendships and other psychosocial difficulties more frequently than do their normally-hearing peers (Most, 2007; Stinson & Whitimire, 2000), and some studies show that this is the same for some children with cochlear implants (Boyd et al.,2000; Dammeyer, 2010; Leigh et al., 2009). Older children with cochlear implants (aged 9-14 years) are generally more affected by loneliness than younger children (aged 5-9 years), with children who receive their implants when older being most affected (Schorr, 2006). This may reflect the fact that social interaction becomes increasingly complex in adolescence, and peer group size tends to increase at this time, making communication more difficult due to increased acoustic and social challenges (Bat-

Unsurprisingly, loneliness and psychosocial difficulties are greatest for children with additional disabilities, particularly those with low speech intelligibility and poor communication skills, as this increases communication breakdown and results in poorer peer attitudes towards children with these difficulties, who may be rejected or ignored by their peers (Dammeyer, 2010; Hintermair, 2007; Most, 2007; van Gent et al., 2007). Conversely, other studies have found no increased incidence of loneliness and psychosocial difficulties in children with cochlear implants compared to children with normal hearing (Percy-Smith et al., 2008a; Schorr, 2006), and children have been observed by parents to have improved communication skills and social relationships as a result of cochlear implantation (Archbold et al., 2008b; Bat-Chava & Deignan, 2001; Bat-Chava et al., 2005; Huber, 2005; Huttunen & Valimaa, 2010). Children with cochlear implants have been reported to be more likely to be acculturated to hearing society than those with a severe-profound hearing loss

A statistically significant association has also been found between the level of social wellbeing in children with cochlear implants and their speech perception, production and

cochlear implants show mixed results (Martin et al., 2011).

Chava & Deignan, 2001; Martin et al., 2011).

using hearing aids (Leigh et al., 2008a).

language skills (Dammeyer, 2010; Percy-Smith et al., 2008b). Social development usually follows language skill development, and improvements in both have been observed to occur more quickly for children with cochlear implants than for children with severe-profound hearing loss using hearing aids (Bat-Chava et al., 2005). It has been suggested that improved spoken language and communication skills facilitate psychosocial development through an ability to communicate and a subsequent increase in confidence (Bat-Chava & Deignan, 2001). Children with severe-profound deafness have historically been found to have lower levels of self-esteem than their peers with normal hearing (Nicholas & Geers, 2003), with the self-esteem of adolescents being lower than that of younger children (Schorr, 2006). It has been suggested that unless their language skills match those of their hearing peers, children with cochlear implants cannot fully integrate into the hearing community and develop positive self-esteem (Crouch, 1997; Lane & Grodin, 1997). However, as with many recent outcomes for children with cochlear implants, more recent research has shown equivalent levels of self esteem in children with cochlear implants and children with normal hearing (Loy et al., 2010; Martin et al., 2011; Sahli & Belgin, 2006).

Recent studies have also used measures of health-related quality of life (QOL) to investigate psychosocial development in children with cochlear implants, using both parental and child reports. QOL is considered to be an assessment of well-being across various areas of life such as social interaction, school adjustment, friendships, communication, and listening ability. Although a potential limitation of QOL measures can be that although parents are well-informed of their children's level of physical functioning, they have a tendency to underestimate their psychosocial functioning (Zaidman-Zait, 2011), QOL assessments are still regarded as a useful method of obtaining a more holistic measure of benefit. Loy and colleagues (2010) found no significant differences between overall reported QOL for children with cochlear implants compared to their peers with normal hearing, in either younger (8-11 years) or older (12-16 years) groups, although the younger group rated QOL more highly than did the adolescent group. Others have reported similar findings for children of various ages (Huber, 2005; Warner-Czyz et al., 2009).

Several factors have been found to influence psychosocial development in children with cochlear implants. Children who are implanted earlier and therefore have a longer duration of implant use are reported to be more socially competent (Leigh et al., 2008a; Martin et al., 2011), with girls outperforming boys (Martin et al., 2011; Nicholas & Geers, 2003; Percy-Smith et al., 2008b). As mentioned earlier, children implanted at older ages appear to be at greater risk of loneliness (Schorr, 2006), and it has been suggested that this may be due to the fact that they do not develop feelings of belonging and inclusion at a young age, as do children with normal hearing, due to their delayed language prior to implantation. It is also reported that children with cochlear implants in mainstream educational settings who are exposed to spoken, rather than signed, language at home have a higher level of social wellbeing (Percy-Smith et al., 2008b; van Gent et al., 2007). This may be because children in these settings are more likely to have hearing parents, and therefore are continuing to speak their first language in these settings, rather than using sign language at home and spoken language at school, as would children of many deaf parents. There is also no evidence that children with cochlear implants in mainstream educational settings, where speech is used exclusively for communication, have an increased incidence of social or emotional difficulties compared to children in special educational settings (Filipo et al., 1999; Nicholas & Geers, 2003; Percy-Smith et al., 2008b).

Cochlear Implants in Children: A Review 347

Sweet, 1990). Phonological processing occurs when a child analyses words into their constituent parts, repeats strings of syllables that form new words, or quickly names common words. These processing abilities enable word decoding to occur, which in turn facilitates word recognition and comprehension of word meaning. Delayed phonological awareness, and a subsequently delayed vocabulary, makes it difficult to learn to read. Further compounding this difficulty is the fact that reading is a skill that must be learned through explicit instruction, some of which may be 'missed' due to compromised perceptual abilities caused by hearing loss, and also through an inability to understand some of the instruction due to poorer language skills (Moeller et al., 2007). It has been shown, however, that vocabulary development accelerates after cochlear implantation (Connor et al., 2006; Dawson, 1995; Geers et al., 2007; Johnson & Goswami, 2010; Nicholas & Geers, 2008), although there are conflicting reports regarding whether vocabulary growth rates slow over time, particularly for children who received their cochlear implants at older ages (El-Hakim et al., 2001) or remain constant (James et al., 2007). There is wide variability in vocabulary development between children (Connor et al., 2000), and long-term follow up of some children in their teen or early adult years still documents many children not having attained

Reading outcomes to date for children with cochlear implants are promising, with evidence that children with cochlear implants are often achieving better reading outcomes at a faster rate than their peers with hearing loss who use hearing aids (Marschark et al., 2007), although many children are still significantly delayed. The number of children with cochlear implants who achieve age-appropriate reading skills is increasing (Geers, 2002; 2003). It has also been documented that almost 4 times as many children who have used a cochlear implant for at least 2 years have achieved a reading level beyond that of fourth grade compared to children with severe-profound hearing loss of similar ages using hearing aids (Spencer et al., 2003; Vermeulen et al., 2007). Higher levels of reading performance have been documented for girls than for boys (Moog & Geers, 2003), as has been observed in children with normal hearing. As with normally-hearing children, the factor that most affects reading outcome is language ability (Connor & Zwolan, 2004; Geers, 2003; Johnson & Goswami, 2010; Spencer et al., 2003), with children who are more competent in producing an oral narrative attaining better reading comprehension skills (Crosson & Geers, 2001). Cognitive ability (Geers & Hayes, 2011), speech intelligibility and speech perception ability have also been shown to be strong predictive factors of reading outcomes (Geers, 2003;

There is increasing evidence that some children with cochlear implants can not only acquire better reading outcomes than their peers with hearing aids, but can even achieve similar outcomes to their peers with normal hearing (Archbold et al., 2008a; Spencer et al., 2003; Spencer & Oleson, 2008). James and colleagues (2008) reported that children implanted between the ages of 2 to 3.6 years achieved reading scores that were within one standard deviation of the hearing normative mean, scoring higher than children implanted between ages 5 and 7 years. Geers and Hayes (2011) also documented 47-66% of adolescents who received their implants as pre-schoolers achieving reading abilities within the average range for their hearing peers. Other studies have reported similar results, with 70%, 61%, and 51% of children reading within age-appropriate levels (Moog, 2002; Geers, 2003, Johnson &

age-appropriate vocabulary (Uziel et al., 2007).

Johnson & Goswami, 2010; Spencer & Oleson, 2008).

Goswami, 2010 respectively).

Once again, there is enormous variability between individuals in their communication and social development after cochlear implantation, with some children progressing at, or even above, the average rate of children with normal hearing, and others who lag behind their peers. Although there appear to be no negative reports on social/emotional development of children as a result of cochlear implantation, a cochlear implant will not guarantee that the social difficulties experienced by many children with severe-profound hearing loss are avoided (Punch & Hyde, 2011). The research does offer hope, however, that an early cochlear implant may not only facilitate the development of speech and language skills, but can also give children the potential to develop a healthy and positive social identity and competent interactional skills.

#### **3.6 Literacy and academic outcomes**

With documented improvements in speech perception, production and language outcomes clearly attributable to the improved auditory access provided by cochlear implants, there has been an expectation that academic outcomes for children with cochlear implants would also improve, with implanted children showing significantly better performance than their peers with hearing aids. However, although the proportion of children with cochlear implants who are enrolled in mainstreamed education settings is increasing steadily (Geers & Brenner, 2003), the degree to which cochlear implants have impacted on academic outcomes in children with severe-profound hearing loss is not yet clear. Much of the research on children with hearing loss is limited mainly to studies of reading ability, and few children who have received cochlear implants at a young age are currently old enough for longer-term outcomes to be measured.

Many children with severe-profound hearing loss, including those with cochlear implants, have 4 to 5 year delays in spoken language development by the time they enter secondary school (Blamey et al., 2001a; Dahl et al., 2003; Davis & Hind, 1999; Ramkalawan & Davis, 1992; Sarant et al., 2009). Generally, the greater the degree of hearing loss, the larger the language delay (Boothroyd et al., 1991). It is well known that poor spoken language ability is a primary cause of difficulty in learning to read for children with normal hearing, and it is therefore unsurprising that literacy achievement for children with hearing loss has historically been low, with many children failing to progress in reading beyond the identification of a limited number of words, or the fourth grade level of primary school (Geers et al., 2008; Moeller et al., 2007). Reported rates of progress have varied from 1 to 6 months for every year of education, with the delay in reading widening in adolescence (Geers et al., 2008; Thoutenhoofd, 2006). A significant proportion of graduating students with hearing loss are functionally illiterate (Helfand, 2001; Moeller et al., 2007; Traxler, 2000; Walker et al., 1998), having not even acquired mastery of spoken language, which is necessary not only for the development of literacy but also for the development of literate thought (Paul 1998). Low literacy achievement and low academic outcomes have seriously impacted on the ability of many children with hearing loss to obtain employment as adults, with resulting low skill employment and reduced income for some, and others simply not having sufficient literacy skills to succeed in the workplace at all.

One of the key language skills required for learning to read is vocabulary, which is often limited in children with hearing loss due to phonetic and phonological delays (Connor & Zwolan, 2004; James et al., 2008; Johnson & Goswami, 2010; Moeller et al., 2007; Moores &

Once again, there is enormous variability between individuals in their communication and social development after cochlear implantation, with some children progressing at, or even above, the average rate of children with normal hearing, and others who lag behind their peers. Although there appear to be no negative reports on social/emotional development of children as a result of cochlear implantation, a cochlear implant will not guarantee that the social difficulties experienced by many children with severe-profound hearing loss are avoided (Punch & Hyde, 2011). The research does offer hope, however, that an early cochlear implant may not only facilitate the development of speech and language skills, but can also give children the potential to develop a healthy and positive social identity and

With documented improvements in speech perception, production and language outcomes clearly attributable to the improved auditory access provided by cochlear implants, there has been an expectation that academic outcomes for children with cochlear implants would also improve, with implanted children showing significantly better performance than their peers with hearing aids. However, although the proportion of children with cochlear implants who are enrolled in mainstreamed education settings is increasing steadily (Geers & Brenner, 2003), the degree to which cochlear implants have impacted on academic outcomes in children with severe-profound hearing loss is not yet clear. Much of the research on children with hearing loss is limited mainly to studies of reading ability, and few children who have received cochlear implants at a young age are currently old enough

Many children with severe-profound hearing loss, including those with cochlear implants, have 4 to 5 year delays in spoken language development by the time they enter secondary school (Blamey et al., 2001a; Dahl et al., 2003; Davis & Hind, 1999; Ramkalawan & Davis, 1992; Sarant et al., 2009). Generally, the greater the degree of hearing loss, the larger the language delay (Boothroyd et al., 1991). It is well known that poor spoken language ability is a primary cause of difficulty in learning to read for children with normal hearing, and it is therefore unsurprising that literacy achievement for children with hearing loss has historically been low, with many children failing to progress in reading beyond the identification of a limited number of words, or the fourth grade level of primary school (Geers et al., 2008; Moeller et al., 2007). Reported rates of progress have varied from 1 to 6 months for every year of education, with the delay in reading widening in adolescence (Geers et al., 2008; Thoutenhoofd, 2006). A significant proportion of graduating students with hearing loss are functionally illiterate (Helfand, 2001; Moeller et al., 2007; Traxler, 2000; Walker et al., 1998), having not even acquired mastery of spoken language, which is necessary not only for the development of literacy but also for the development of literate thought (Paul 1998). Low literacy achievement and low academic outcomes have seriously impacted on the ability of many children with hearing loss to obtain employment as adults, with resulting low skill employment and reduced income for some, and others simply not

One of the key language skills required for learning to read is vocabulary, which is often limited in children with hearing loss due to phonetic and phonological delays (Connor & Zwolan, 2004; James et al., 2008; Johnson & Goswami, 2010; Moeller et al., 2007; Moores &

competent interactional skills.

**3.6 Literacy and academic outcomes** 

for longer-term outcomes to be measured.

having sufficient literacy skills to succeed in the workplace at all.

Sweet, 1990). Phonological processing occurs when a child analyses words into their constituent parts, repeats strings of syllables that form new words, or quickly names common words. These processing abilities enable word decoding to occur, which in turn facilitates word recognition and comprehension of word meaning. Delayed phonological awareness, and a subsequently delayed vocabulary, makes it difficult to learn to read. Further compounding this difficulty is the fact that reading is a skill that must be learned through explicit instruction, some of which may be 'missed' due to compromised perceptual abilities caused by hearing loss, and also through an inability to understand some of the instruction due to poorer language skills (Moeller et al., 2007). It has been shown, however, that vocabulary development accelerates after cochlear implantation (Connor et al., 2006; Dawson, 1995; Geers et al., 2007; Johnson & Goswami, 2010; Nicholas & Geers, 2008),

although there are conflicting reports regarding whether vocabulary growth rates slow over time, particularly for children who received their cochlear implants at older ages (El-Hakim et al., 2001) or remain constant (James et al., 2007). There is wide variability in vocabulary development between children (Connor et al., 2000), and long-term follow up of some children in their teen or early adult years still documents many children not having attained age-appropriate vocabulary (Uziel et al., 2007).

Reading outcomes to date for children with cochlear implants are promising, with evidence that children with cochlear implants are often achieving better reading outcomes at a faster rate than their peers with hearing loss who use hearing aids (Marschark et al., 2007), although many children are still significantly delayed. The number of children with cochlear implants who achieve age-appropriate reading skills is increasing (Geers, 2002; 2003). It has also been documented that almost 4 times as many children who have used a cochlear implant for at least 2 years have achieved a reading level beyond that of fourth grade compared to children with severe-profound hearing loss of similar ages using hearing aids (Spencer et al., 2003; Vermeulen et al., 2007). Higher levels of reading performance have been documented for girls than for boys (Moog & Geers, 2003), as has been observed in children with normal hearing. As with normally-hearing children, the factor that most affects reading outcome is language ability (Connor & Zwolan, 2004; Geers, 2003; Johnson & Goswami, 2010; Spencer et al., 2003), with children who are more competent in producing an oral narrative attaining better reading comprehension skills (Crosson & Geers, 2001). Cognitive ability (Geers & Hayes, 2011), speech intelligibility and speech perception ability have also been shown to be strong predictive factors of reading outcomes (Geers, 2003; Johnson & Goswami, 2010; Spencer & Oleson, 2008).

There is increasing evidence that some children with cochlear implants can not only acquire better reading outcomes than their peers with hearing aids, but can even achieve similar outcomes to their peers with normal hearing (Archbold et al., 2008a; Spencer et al., 2003; Spencer & Oleson, 2008). James and colleagues (2008) reported that children implanted between the ages of 2 to 3.6 years achieved reading scores that were within one standard deviation of the hearing normative mean, scoring higher than children implanted between ages 5 and 7 years. Geers and Hayes (2011) also documented 47-66% of adolescents who received their implants as pre-schoolers achieving reading abilities within the average range for their hearing peers. Other studies have reported similar results, with 70%, 61%, and 51% of children reading within age-appropriate levels (Moog, 2002; Geers, 2003, Johnson & Goswami, 2010 respectively).

Cochlear Implants in Children: A Review 349

subtests of the Woodcock-Johnson Tests of Achievement (the expected average score for children with normal hearing would be 100). This study is novel because it is the only report of fully comparable academic performance for children with cochlear implants. A more recent report on educational and employment achievements in France showed that although 42-61% of the children had failed one grade (or year level) at school (a higher rate of failure than for children with normal hearing), over 60% of those aged 18 years and over either held a university degree and/or were employed at levels similar to those of their peers with normal hearing. These figures were reported as being very similar to those for the general population of France, where 53% of individuals have at least a high school diploma (Venail et al., 2010). A third study of Malaysian children reported that for children implanted relatively late (aged 3-4 years), 56% performed below the average level academically, with

As with other areas of development, wide variability in literacy and academic outcomes has been reported. As children are implanted at younger ages and enter school with better language skills, it is likely that future research will show a further narrowing of the gap in literacy and academic performance between children with cochlear implants and children with normal hearing. However, although many younger children are reported to be performing at age appropriate levels, some studies suggest that this level of performance is not sustained long-term by all children. Currently, the effect of cochlear implants on the

**4. Factors affecting speech perception, production and language outcomes**  Despite the significant improvements made in cochlear implant technology, and the large body of clinical knowledge gained over time regarding likely benefits for children with cochlear implants, one of the remaining significant challenges is to identify predictors of post-implant outcomes, as there is great variation in benefits between individuals. Several factors have currently been identified as influential in children's speech perception, speech production, language and academic development after implantation, and the most

With the establishment of newborn hearing screening in many developed countries around the world, the average age of diagnosis of hearing loss in these countries has dropped to 12- 25 months, with many babies identified as young as 3 months of age (Dalzell et al., 2000; Harrison et al., 2003; Watkin et al., 2007). As mentioned previously, the earlier identification of hearing loss has resulted in a rapid rise in the numbers of children receiving cochlear implants at younger ages (ASHA, 2004). It was estimated that the number of children receiving cochlear implants before the age of 2 years between 1991 and 2002 increased forty fold (Drinkwater, 2004), and it is likely that this growth rate has not declined. However, there are still many children in developed countries who are not receiving cochlear implants early in life. It is disappointing to note that despite earlier identification of hearing loss through newborn hearing screening programs, many families (and almost half of the families in the U.S. who are referred for further hearing assessment of their newborn babies) still do not receive early intervention services by the age of 6 months, as is recommended by the 2007 Position Statement of the Joint Committee on Infant Hearing (JCIH, 2007). The

greatest achievement in mathematics rather than language (Mukari et al., 2007).

long-term academic outcomes of children appears promising, but unclear.

important of these are discussed below.

**4.1 Age at diagnosis** 

Other studies have shown that although early cochlear implantation facilitates improved reading outcomes in terms of both decoding and reading comprehension, a significant number of children are still not reading at the same level as their normally-hearing peers, and are falling behind over time (Archbold et al., 2008a; Connor & Zwolan, 2004). Geers and colleagues showed that only 44% of secondary school students showed age-appropriate reading performance, compared to 56% of the same group when in primary (elementary) school (Geers et al., 2008). Although the group of children was reading, on average, at an age-appropriate level when aged 8-9 years, the same children were delayed on average by almost 2 years in their reading by age 15-16 years. More recently, Geers and Hayes (2011) also reported that although 72% of the adolescents in the same sample had retained their reading standing in comparison with hearing peers since primary school, (demonstrating age-appropriate growth in reading skills over that time), 60% were still delayed overall. For many children, the reading gap between children with cochlear implants and their peers with normal hearing still widens as they grow older. Some studies still report that some children still do not make any progress at all (James et al., 2008).

Studies of writing in children with hearing loss have evaluated syntax (or grammar), looking specifically at complexity, productivity and grammaticality. The writing of children with hearing loss has generally been found to be composed of shorter sentences than those used by their hearing peers (Kretchmer & Kretchmer, 1986), repetitive phrasing, and many subject-object-verb constructions (Lichtenstein, 1998; Wilbur, 1977). There are also many errors of omission, substitution and word addition (Myklebust, 1964), including the omission of articles, prepositions, copulas, pronouns and conjunctions (Crosson & Geers, 2001). Lichtenstein also noted many errors of morphology such as plurality, verb agreement and tense in the writing of children with hearing loss. It has been concluded that children with hearing loss have even greater difficulties with writing than with learning to read (Paul, 1998).

During the primary (or elementary) school years, early writing patterns appear to follow those of spoken language development (ie. children write as they would speak). As their writing skills develop, they use more sophisticated forms of language so that their writing becomes more "detached" from their spoken language (Spencer et al., 2003). Children with cochlear implants are reported to persist in the documented pattern of immature writing skills, with shorter, less complex sentences containing more errors reported for a group of 9 year-old children using cochlear implants (Spencer et al., 2003). In this study, correlations between language abilities and writing productivity suggested that the children had not yet 'detached' their written from their spoken language. Geers and Hayes (2011) also documented the poor spelling and writing skills of children with cochlear implants compared to their peers with normal hearing. Children in this study continued to struggle with phonological processing tasks, and performed at delayed levels on measures of phonological awareness, expository writing, and spelling.

Academic success relies on reading and writing abilities, and there is now a body of work focused on literacy in children with cochlear implants. However, information on overall academic performance of these children is scarce. Spencer and colleagues (2004) examined academic achievement in science, social studies and humanities in young adults with cochlear implants, finding that consistent users of cochlear implants performed comparably to their hearing peers, achieving an overall mean standard score of 103.88 on the relevant

Other studies have shown that although early cochlear implantation facilitates improved reading outcomes in terms of both decoding and reading comprehension, a significant number of children are still not reading at the same level as their normally-hearing peers, and are falling behind over time (Archbold et al., 2008a; Connor & Zwolan, 2004). Geers and colleagues showed that only 44% of secondary school students showed age-appropriate reading performance, compared to 56% of the same group when in primary (elementary) school (Geers et al., 2008). Although the group of children was reading, on average, at an age-appropriate level when aged 8-9 years, the same children were delayed on average by almost 2 years in their reading by age 15-16 years. More recently, Geers and Hayes (2011) also reported that although 72% of the adolescents in the same sample had retained their reading standing in comparison with hearing peers since primary school, (demonstrating age-appropriate growth in reading skills over that time), 60% were still delayed overall. For many children, the reading gap between children with cochlear implants and their peers with normal hearing still widens as they grow older. Some studies still report that some

Studies of writing in children with hearing loss have evaluated syntax (or grammar), looking specifically at complexity, productivity and grammaticality. The writing of children with hearing loss has generally been found to be composed of shorter sentences than those used by their hearing peers (Kretchmer & Kretchmer, 1986), repetitive phrasing, and many subject-object-verb constructions (Lichtenstein, 1998; Wilbur, 1977). There are also many errors of omission, substitution and word addition (Myklebust, 1964), including the omission of articles, prepositions, copulas, pronouns and conjunctions (Crosson & Geers, 2001). Lichtenstein also noted many errors of morphology such as plurality, verb agreement and tense in the writing of children with hearing loss. It has been concluded that children with hearing loss have even greater difficulties with writing than with learning to read

During the primary (or elementary) school years, early writing patterns appear to follow those of spoken language development (ie. children write as they would speak). As their writing skills develop, they use more sophisticated forms of language so that their writing becomes more "detached" from their spoken language (Spencer et al., 2003). Children with cochlear implants are reported to persist in the documented pattern of immature writing skills, with shorter, less complex sentences containing more errors reported for a group of 9 year-old children using cochlear implants (Spencer et al., 2003). In this study, correlations between language abilities and writing productivity suggested that the children had not yet 'detached' their written from their spoken language. Geers and Hayes (2011) also documented the poor spelling and writing skills of children with cochlear implants compared to their peers with normal hearing. Children in this study continued to struggle with phonological processing tasks, and performed at delayed levels on measures of

Academic success relies on reading and writing abilities, and there is now a body of work focused on literacy in children with cochlear implants. However, information on overall academic performance of these children is scarce. Spencer and colleagues (2004) examined academic achievement in science, social studies and humanities in young adults with cochlear implants, finding that consistent users of cochlear implants performed comparably to their hearing peers, achieving an overall mean standard score of 103.88 on the relevant

children still do not make any progress at all (James et al., 2008).

phonological awareness, expository writing, and spelling.

(Paul, 1998).

subtests of the Woodcock-Johnson Tests of Achievement (the expected average score for children with normal hearing would be 100). This study is novel because it is the only report of fully comparable academic performance for children with cochlear implants. A more recent report on educational and employment achievements in France showed that although 42-61% of the children had failed one grade (or year level) at school (a higher rate of failure than for children with normal hearing), over 60% of those aged 18 years and over either held a university degree and/or were employed at levels similar to those of their peers with normal hearing. These figures were reported as being very similar to those for the general population of France, where 53% of individuals have at least a high school diploma (Venail et al., 2010). A third study of Malaysian children reported that for children implanted relatively late (aged 3-4 years), 56% performed below the average level academically, with greatest achievement in mathematics rather than language (Mukari et al., 2007).

As with other areas of development, wide variability in literacy and academic outcomes has been reported. As children are implanted at younger ages and enter school with better language skills, it is likely that future research will show a further narrowing of the gap in literacy and academic performance between children with cochlear implants and children with normal hearing. However, although many younger children are reported to be performing at age appropriate levels, some studies suggest that this level of performance is not sustained long-term by all children. Currently, the effect of cochlear implants on the long-term academic outcomes of children appears promising, but unclear.
