**1. Introduction**

Autism Spectrum Disorders (ASD) are developmental disorders that people are burdened with for their whole life. They origin in childhood and are featured by restrictions in social and emotional development, communication, interests and motor skills [1]. People with au‐ tism are characterized by three major deficits as defined by the most recent version of diag‐ nostic and statistical manual of mental disorders (DSM-IV-TR). These deficits include qualitative impairments in social interaction, qualitative impairments in communication and restricted, repetitive and stereotyped patterns of behaviour [2]. Behaviours within these main components of ASD may differ per individual because they are expressed in unique ways for each individual. Variations can be found in the way, the intensity and the persever‐ ance with which the symptoms are expressed. Also the core characteristics may vary per in‐ dividual. Where skills, interests and intellectual levels differ between people, so do the characteristics of autism, only the main problem areas remain the same [3]. In the current chapter, not only autism as defined by DSM-IV-TR, but also all variations within the autistic spectrum will be included.

Several symptoms of ASD are not unique but also found in other groups of people with disabilities. Similar behaviours, overlapping symptoms, or even the exact same behaviou‐ ral characteristics can be found in people with hearing disabilities [4], visual impair‐ ments [5], intellectual disabilities [6] and combinations of these impairments, such as deafblindness [7]. All three of the main components of autism that the DSM-IV-TR de‐ scribes, are also found in non autistic people with sensory and intellectual disabilities.

© 2013 De Vaan et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Furthermore, the prevalence of ASD seems to be much higher in people with one or more of these disabilities. In the entire population ASD is estimated to occur in at least between 0,1 and 0,6 percent [8, 9] and at most 2,64 percent [10]. In people with intellec‐ tual disabilities reported prevalences are much higher, ranging from 4 up to 60 percent [11]. Without giving exact rates the prevalence of ASD and autistic features in people with sensory disabilities is reported to be much higher than in typically developing peo‐ ple [12-14] It is an interesting question what cause this increase in prevalence when oth‐ er impairments are involved. An obvious explanation could be a relationship between ASD and sensory or intellectual disabilities. An alternative explanation is an overlap of symptoms, but not of the underlying mechanisms, between autistic people without other disabilities and people with sensory and intellectual impairments. If the latter is the case, some people might be unfairly diagnosed as autistic when in fact they are not. False pos‐ itive diagnoses then causes the increase in prevalence of ASD in sensory, intellectually and multiply impaired people.

**2.1. Reciprocity and peer relationships**

the severity of the social impairments.

jects than people [19].

hearing population.

Some children with ASD prefer doing things alone and might avoid all kinds of social play [2]. Lack of reciprocity is also shown in an aversion to social touch and in problems with responding to your own name [21]. In young children impairments in this area are often ex‐ pressed as inappropriate responses towards other people and being more interested in ob‐

Autism Spectrum Disorders in People with Sensory and Intellectual Disabilities – Symptom Overlap and Differentiating

Characteristics

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http://dx.doi.org/10.5772/53714

Autistic people may find it difficult to engage in peer relationships. However, they are not the only ones that have trouble in this area. A recent study about the popularity of deaf chil‐ dren showed that deaf children were less accepted and less popular than their hearing peers. This was explained by them being, amongst others variables, more withdrawn, less prosocial and worse at monitoring a conversation [22], behaviours also typical for ASD in a

People with intellectual disabilities show problems in the area of reciprocity and relation‐ ships too. Often, intellectual disabilities are caused by abnormalities in the brain. It is not surprising to find that these abnormalities cause problems in people's emotional and social behaviours. However, not everyone with serious intellectual disabilities has social or emo‐ tional problems, some of them are even overly interested in social contact. Reciprocity and engagement are definitely present while communicating with them [3]. According to Wing [23] one can spot the difference between impaired social behaviour in intellectually im‐ paired people with ASD versus intellectually impaired people without ASD by looking at

The problems in reciprocity and developing relationships are not limited to people with ASD, and auditory or mental disabilities. In 1977 Selma Fraiberg described the development of blind children. She noticed that blind children do not reach out to their parents as much as their sighted peers do. This may appear as a lack of reciprocity, when in fact seeing a pa‐ rent makes sighted children reach out. Blind children obviously lack this ability [24]. This explains their less frequent attempts in reaching out, without any relationship with reci‐ procity. Moreover, according to Fraiberg, the absence of reaching out could make parents less responsive to their children, restraining them in their development of relationships. She explains that in the sighted, the smallest amount of eye contact with a baby can make an adult talk or play with them [24]. When signals such as reaching out and making eye contact are absent, the development of reciprocity and relationships could be impaired because of this. In fact, because the care for a blind child is so much more challenging and reciprocal signals are easily missed, lack of vision may increase the risk of problems in attachment [18]. However, Warren stressed that despite an increased risk, attachment problems can be avoided if the parents of a blind child respond appropriately. Assessing attachment high‐ lights another problem, that is the reliability and validity of assessment instruments and procedures in children with disabilities. Attachment in sighted children is often tested by the strange situation method [25] where a child's reaction upon reunion with its mother is assessed after it has been left alone or in the presence of a stranger. Children with visual im‐ pairments, especially blind children, may not notice the departure and reappearance of their mother and may therefore fail to respond like sighted children would do [18]. In this case

The overlap in symptoms between people with ASD and people with sensory, intellectual and multiple impairments interferes with the right classification of the behaviour of people with sensory and intellectual disabilities. Several authors stress that even though the symp‐ toms are similar, the processes that underlie these symptoms are different for autistic versus non autistic people [4, 15, 16]. Nevertheless, when behaviours are the same, there is the risk that ASD is either missed or unjustly diagnosed. A wrong classification may lead to a wrong treatment plan, which is especially problematic if the treatment plan is counterproductive for the true underlying cause. A treatment is most effective if it tackles the cause of the be‐ haviours. An example is the stopping of stereotyped movements. Whereas in the blind these are usually caused by a lack of stimulation from the environment [17, 18], in people with ASD stereotyped movements can occur to get away from too much stimulation from the en‐ vironment [19, 20].

The current chapter will give a comprehensive overview of the overlapping symptoms be‐ tween autistic and non autistic people; it will elaborate on the categories that the DSM-IV-TR distinguishes as well as on the overlap within these categories for autistic and nonautistic people, it will describe the differences between the two groups and finally explain why a better differentiation is necessary.

### **2. Qualitative impairments in social interaction**

The first characteristic of autism, according to DSM-IV-TR is defined as qualitative impair‐ ments in social interaction. These impairments can express through a variety of symptoms: problems in reciprocity and sharing of interests and emotions; impairments in non-verbal behaviours and impairments in joint attention, either in sharing, following or directing [2]. All of these problems in social behaviours contribute to problems in the development of proper peer relations.

### **2.1. Reciprocity and peer relationships**

Furthermore, the prevalence of ASD seems to be much higher in people with one or more of these disabilities. In the entire population ASD is estimated to occur in at least between 0,1 and 0,6 percent [8, 9] and at most 2,64 percent [10]. In people with intellec‐ tual disabilities reported prevalences are much higher, ranging from 4 up to 60 percent [11]. Without giving exact rates the prevalence of ASD and autistic features in people with sensory disabilities is reported to be much higher than in typically developing peo‐ ple [12-14] It is an interesting question what cause this increase in prevalence when oth‐ er impairments are involved. An obvious explanation could be a relationship between ASD and sensory or intellectual disabilities. An alternative explanation is an overlap of symptoms, but not of the underlying mechanisms, between autistic people without other disabilities and people with sensory and intellectual impairments. If the latter is the case, some people might be unfairly diagnosed as autistic when in fact they are not. False pos‐ itive diagnoses then causes the increase in prevalence of ASD in sensory, intellectually

The overlap in symptoms between people with ASD and people with sensory, intellectual and multiple impairments interferes with the right classification of the behaviour of people with sensory and intellectual disabilities. Several authors stress that even though the symp‐ toms are similar, the processes that underlie these symptoms are different for autistic versus non autistic people [4, 15, 16]. Nevertheless, when behaviours are the same, there is the risk that ASD is either missed or unjustly diagnosed. A wrong classification may lead to a wrong treatment plan, which is especially problematic if the treatment plan is counterproductive for the true underlying cause. A treatment is most effective if it tackles the cause of the be‐ haviours. An example is the stopping of stereotyped movements. Whereas in the blind these are usually caused by a lack of stimulation from the environment [17, 18], in people with ASD stereotyped movements can occur to get away from too much stimulation from the en‐

The current chapter will give a comprehensive overview of the overlapping symptoms be‐ tween autistic and non autistic people; it will elaborate on the categories that the DSM-IV-TR distinguishes as well as on the overlap within these categories for autistic and nonautistic people, it will describe the differences between the two groups and finally explain

The first characteristic of autism, according to DSM-IV-TR is defined as qualitative impair‐ ments in social interaction. These impairments can express through a variety of symptoms: problems in reciprocity and sharing of interests and emotions; impairments in non-verbal behaviours and impairments in joint attention, either in sharing, following or directing [2]. All of these problems in social behaviours contribute to problems in the development of

and multiply impaired people.

480 Recent Advances in Autism Spectrum Disorders - Volume I

vironment [19, 20].

proper peer relations.

why a better differentiation is necessary.

**2. Qualitative impairments in social interaction**

Some children with ASD prefer doing things alone and might avoid all kinds of social play [2]. Lack of reciprocity is also shown in an aversion to social touch and in problems with responding to your own name [21]. In young children impairments in this area are often ex‐ pressed as inappropriate responses towards other people and being more interested in ob‐ jects than people [19].

Autistic people may find it difficult to engage in peer relationships. However, they are not the only ones that have trouble in this area. A recent study about the popularity of deaf chil‐ dren showed that deaf children were less accepted and less popular than their hearing peers. This was explained by them being, amongst others variables, more withdrawn, less prosocial and worse at monitoring a conversation [22], behaviours also typical for ASD in a hearing population.

People with intellectual disabilities show problems in the area of reciprocity and relation‐ ships too. Often, intellectual disabilities are caused by abnormalities in the brain. It is not surprising to find that these abnormalities cause problems in people's emotional and social behaviours. However, not everyone with serious intellectual disabilities has social or emo‐ tional problems, some of them are even overly interested in social contact. Reciprocity and engagement are definitely present while communicating with them [3]. According to Wing [23] one can spot the difference between impaired social behaviour in intellectually im‐ paired people with ASD versus intellectually impaired people without ASD by looking at the severity of the social impairments.

The problems in reciprocity and developing relationships are not limited to people with ASD, and auditory or mental disabilities. In 1977 Selma Fraiberg described the development of blind children. She noticed that blind children do not reach out to their parents as much as their sighted peers do. This may appear as a lack of reciprocity, when in fact seeing a pa‐ rent makes sighted children reach out. Blind children obviously lack this ability [24]. This explains their less frequent attempts in reaching out, without any relationship with reci‐ procity. Moreover, according to Fraiberg, the absence of reaching out could make parents less responsive to their children, restraining them in their development of relationships. She explains that in the sighted, the smallest amount of eye contact with a baby can make an adult talk or play with them [24]. When signals such as reaching out and making eye contact are absent, the development of reciprocity and relationships could be impaired because of this. In fact, because the care for a blind child is so much more challenging and reciprocal signals are easily missed, lack of vision may increase the risk of problems in attachment [18]. However, Warren stressed that despite an increased risk, attachment problems can be avoided if the parents of a blind child respond appropriately. Assessing attachment high‐ lights another problem, that is the reliability and validity of assessment instruments and procedures in children with disabilities. Attachment in sighted children is often tested by the strange situation method [25] where a child's reaction upon reunion with its mother is assessed after it has been left alone or in the presence of a stranger. Children with visual im‐ pairments, especially blind children, may not notice the departure and reappearance of their mother and may therefore fail to respond like sighted children would do [18]. In this case the perception problems interfere with possible affirmations of attachment problems. The same problems occur when observing people whilst looking for signals of reciprocity or in‐ terest in other people. Because of a loss of sight children with visual impairment or blind‐ ness may not notice other people or other people's behaviour. In extreme cases they do not show any interest in their surroundings because of poor vision and direct all their attention to objects within arm's reach or to their own body. This is especially the case in deafblind children who have not only problems in vision but also hearing, the two distant senses. Their remaining senses (touch, smell, taste and proprioception) only function in nearby space, giving the impression that deafblind children are ego-centred. This ego-centeredness is however of a different origin than it is in ASD [4].

When trying to differentiate autistic behaviours from behaviours due to multiple impair‐ ments, Hoevenaars-van den Boom et al. (2009) showed that even though social behaviours appear similar it is possible to differentiate autistic from non-autistic behaviours. They have found a significant difference between autistic and non-autistic deafblind children with pro‐ found intellectual disabilities in the areas of social and communicative behaviours in that these children showed and openness for contact and pleasure while in social contact [7].

Autism Spectrum Disorders in People with Sensory and Intellectual Disabilities – Symptom Overlap and Differentiating

Characteristics

483

http://dx.doi.org/10.5772/53714

Autistic people have trouble sharing interests, emotions and activities [2]. Related to this is problems in joint attention. Joint attention refers to the ability to share your attention, by looking where someone else is looking at and by sharing your own interests through point‐ ing, gazing, or other non-verbal behaviour [19]. People with ASD may fail to share their emotions, feelings and thoughts but they also can have problems in sharing attention, which is expressed in their inability to follow a pointing finger or the direction of a gaze. This is interesting, because in non-autistic children, both pointing and following a finger or gaze not only relates to the object itself, but also to the other person's feelings and interests for this object. Autistic people fail to point or gaze and follow somebody else's pointing or gaz‐

Joint attention is often said to be a precursor of theory of mind (ToM) [27]. Someone has a ToM when they are capable of attributing a mental state to themselves and to others [28]. ToM is one of the most important constructs regarding a deeper understanding of ASD [29] and can explain many of the symptoms of ASD. Not only social behaviours as joint atten‐ tion, but also symbolic play and language problems such as echolalia and reversal of pro‐ nouns can be attributed to not having a ToM [12, 30]. In simple terms, its refers to being able to realize what people think, feel and want [3]. Having a ToM also entails understanding irony and non-literal language, and can therefore also explain some of the deficits in com‐ munication. Another aspect of ToM is being able to take someone else's point of view or per‐ spective. Perspective taking is often measured with false belief tasks, such as the Sally-Annetask [31]. Baron-Cohen and colleagues used this task to measure false belief in autistic children by showing them two dolls, one called Sally and the other called Anne. They played out a story where Sally had a marble in her basket. Sally left and Anne put the mar‐ ble in her own basket. By asking children questions on where the marble really is and where Sally would think the marble is, perspective taking can be measured [32] and give an indica‐ tion of the development of a ToM. This is a typical false belief task, but many variations have been used since then. Where in sighted children ToM is tested with a false belief task such as the Sally-Anne task [32] or joint attention tasks, these tasks may not be applicable sufficiently enough for children with visual impairment. In addition, joint attention is often measured with gaze direction or pointing, something that blind children are for obvious rea‐ sons incapable of showing and is limited in visually impaired children. Peréz-Pereira and Conti-Ramsden do point out that it is not the pointing or gazing what matters, it is the func‐ tion of this pointing that is of interest [30]. To measure this, things need to be seen from a

ing because they fail to understand other people's interests in the objects [19].

**2.3. Joint attention and theory of mind**

blind person's perspective.

#### **2.2. Verbal and non-verbal social behaviours**

In people with ASD, much verbal and non-verbal behaviour is impaired. This can express itself in to unnatural eye-to-eye gaze, a failure to correctly understand and execute facial ex‐ pressions, atypical body postures and gestures to regulate social interaction. People with ASD often show less eye contact and fewer social smiles to others. They may also show problems in understanding facial expressions and the underlying emotions [19].

Non-verbal behaviours are very important in social communication and are used to make messages more clear. It's hard to imagine communicating without facial expressions, ges‐ tures, posture or understanding gaze direction. People with impairments miss a lot of these signals while communicating. In a visually impaired group it may be hard to distinguish au‐ tistic people from non-autistic people based on non-verbal behaviours. Non-verbal skills that come natural to people without impairments need to be taught specifically to people with visual impairments [20], for example by explaining gestures in a tactile way and in nat‐ ural situations. So even though people with sensory impairments show problems in express‐ ing themselves non-verbally, Gense and Gense [20] do believe that many behaviours can be taught. On the other hand, in visually impaired people some behaviours may be impossible to teach. Making eye contact and following gaze direction are simply infeasible for people with visual impairments. One cannot expect them to show these behaviours. Since their im‐ pairments make some social behaviours impossible to execute, they may use other signs to show their social skills. A blind person will not look someone in the eye when interested in what they have to say, but they may aim their ears towards this person and will thus aim their face in another direction. This behaviour is inappropriate for someone with adequate visual abilities, but the visually impaired will orient with their ears more than with their eyes and it may even point to social interest in another person.

Another complication is that it is important to take into account the severity of intellectual disability when analysing a person's social behaviours. If mental and chronological age do not match, age inappropriate social behaviours might be seen. An example is that people with intellectual disabilities show few gestures and joint attention signs [26]. On the other hand, people with mental retardation and autism responded to their name much less fre‐ quently than did people with mental retardation alone [26], making orientation after hearing ones name a characteristic that may help in differentiating autistic from non-autistic people.

When trying to differentiate autistic behaviours from behaviours due to multiple impair‐ ments, Hoevenaars-van den Boom et al. (2009) showed that even though social behaviours appear similar it is possible to differentiate autistic from non-autistic behaviours. They have found a significant difference between autistic and non-autistic deafblind children with pro‐ found intellectual disabilities in the areas of social and communicative behaviours in that these children showed and openness for contact and pleasure while in social contact [7].

#### **2.3. Joint attention and theory of mind**

the perception problems interfere with possible affirmations of attachment problems. The same problems occur when observing people whilst looking for signals of reciprocity or in‐ terest in other people. Because of a loss of sight children with visual impairment or blind‐ ness may not notice other people or other people's behaviour. In extreme cases they do not show any interest in their surroundings because of poor vision and direct all their attention to objects within arm's reach or to their own body. This is especially the case in deafblind children who have not only problems in vision but also hearing, the two distant senses. Their remaining senses (touch, smell, taste and proprioception) only function in nearby space, giving the impression that deafblind children are ego-centred. This ego-centeredness

In people with ASD, much verbal and non-verbal behaviour is impaired. This can express itself in to unnatural eye-to-eye gaze, a failure to correctly understand and execute facial ex‐ pressions, atypical body postures and gestures to regulate social interaction. People with ASD often show less eye contact and fewer social smiles to others. They may also show

Non-verbal behaviours are very important in social communication and are used to make messages more clear. It's hard to imagine communicating without facial expressions, ges‐ tures, posture or understanding gaze direction. People with impairments miss a lot of these signals while communicating. In a visually impaired group it may be hard to distinguish au‐ tistic people from non-autistic people based on non-verbal behaviours. Non-verbal skills that come natural to people without impairments need to be taught specifically to people with visual impairments [20], for example by explaining gestures in a tactile way and in nat‐ ural situations. So even though people with sensory impairments show problems in express‐ ing themselves non-verbally, Gense and Gense [20] do believe that many behaviours can be taught. On the other hand, in visually impaired people some behaviours may be impossible to teach. Making eye contact and following gaze direction are simply infeasible for people with visual impairments. One cannot expect them to show these behaviours. Since their im‐ pairments make some social behaviours impossible to execute, they may use other signs to show their social skills. A blind person will not look someone in the eye when interested in what they have to say, but they may aim their ears towards this person and will thus aim their face in another direction. This behaviour is inappropriate for someone with adequate visual abilities, but the visually impaired will orient with their ears more than with their

Another complication is that it is important to take into account the severity of intellectual disability when analysing a person's social behaviours. If mental and chronological age do not match, age inappropriate social behaviours might be seen. An example is that people with intellectual disabilities show few gestures and joint attention signs [26]. On the other hand, people with mental retardation and autism responded to their name much less fre‐ quently than did people with mental retardation alone [26], making orientation after hearing ones name a characteristic that may help in differentiating autistic from non-autistic people.

problems in understanding facial expressions and the underlying emotions [19].

eyes and it may even point to social interest in another person.

is however of a different origin than it is in ASD [4].

**2.2. Verbal and non-verbal social behaviours**

482 Recent Advances in Autism Spectrum Disorders - Volume I

Autistic people have trouble sharing interests, emotions and activities [2]. Related to this is problems in joint attention. Joint attention refers to the ability to share your attention, by looking where someone else is looking at and by sharing your own interests through point‐ ing, gazing, or other non-verbal behaviour [19]. People with ASD may fail to share their emotions, feelings and thoughts but they also can have problems in sharing attention, which is expressed in their inability to follow a pointing finger or the direction of a gaze. This is interesting, because in non-autistic children, both pointing and following a finger or gaze not only relates to the object itself, but also to the other person's feelings and interests for this object. Autistic people fail to point or gaze and follow somebody else's pointing or gaz‐ ing because they fail to understand other people's interests in the objects [19].

Joint attention is often said to be a precursor of theory of mind (ToM) [27]. Someone has a ToM when they are capable of attributing a mental state to themselves and to others [28]. ToM is one of the most important constructs regarding a deeper understanding of ASD [29] and can explain many of the symptoms of ASD. Not only social behaviours as joint atten‐ tion, but also symbolic play and language problems such as echolalia and reversal of pro‐ nouns can be attributed to not having a ToM [12, 30]. In simple terms, its refers to being able to realize what people think, feel and want [3]. Having a ToM also entails understanding irony and non-literal language, and can therefore also explain some of the deficits in com‐ munication. Another aspect of ToM is being able to take someone else's point of view or per‐ spective. Perspective taking is often measured with false belief tasks, such as the Sally-Annetask [31]. Baron-Cohen and colleagues used this task to measure false belief in autistic children by showing them two dolls, one called Sally and the other called Anne. They played out a story where Sally had a marble in her basket. Sally left and Anne put the mar‐ ble in her own basket. By asking children questions on where the marble really is and where Sally would think the marble is, perspective taking can be measured [32] and give an indica‐ tion of the development of a ToM. This is a typical false belief task, but many variations have been used since then. Where in sighted children ToM is tested with a false belief task such as the Sally-Anne task [32] or joint attention tasks, these tasks may not be applicable sufficiently enough for children with visual impairment. In addition, joint attention is often measured with gaze direction or pointing, something that blind children are for obvious rea‐ sons incapable of showing and is limited in visually impaired children. Peréz-Pereira and Conti-Ramsden do point out that it is not the pointing or gazing what matters, it is the func‐ tion of this pointing that is of interest [30]. To measure this, things need to be seen from a blind person's perspective.

Seeing things from a blind person's perspective is difficult when it comes to ToM tasks. Conventional ToM tasks have been carried out on people with impaired vision, showing that visually impaired children invariably performed worse than sighted children. McAl‐ pine and Moore did a false belief task using containers with unexpected contents and asked what another person would think was in it. Many of the blind children failed this task, even though sighted children are able to do this at a younger age [33, 34]. A similar study by Min‐ ter, Hobson and Bishop (1998) compared visually impaired with sighted children of the same verbal intelligence, and showed similar results. In their first experiment, they did a similar task as the container task McAlpine and Moore used. They used a warm teapot, fil‐ led with sand instead of tea. Whereas almost all sighted children were able to pass this task, almost half of the visually impaired children failed to answer false belief questions such as: "What did you think was in here?" and "What would he/she think is in here?" The authors note that blind people may have less experience with hot teapots because of the extra dan‐ ger their lack of vision provides. Their second experiment was done with three boxes, where the participants helped the experimenter hide a pencil for another experimenter and false belief questions were asked. Again, the visually impaired children performed worse than the sighted, but much better than on the previous task. The authors think this was because they were more involved in this task, because they helped with the hiding [35]. These find‐ ings show that children with visual impairments do worse on conventional ToM tasks than do their hearing peers. One could assume that blind children do not have a ToM, or develop it slower. However, other findings indicate that visually impaired children can pass a ToM task, given an adapted task. In line with the notion that things need to be seen more from a blind person's perspective, it could be possible that visually impaired people have just as much a ToM as sighted people do; it's only measured in the wrong way. Peterson and her colleagues confirmed this. They state that blind people may very well rely on completely different features of an object than sighted people do in order to decide what another person thinks about an object [36]. They tested if this was true by adapting frequently used false belief tasks. For example, they have changed the famous Sally-Anne task to a Sally-Bill task. In this task, there were no dolls or pictures of children with baskets and marbles, but it was a purely narrative story. The experimenters performed four ToM tasks, including similar tasks to the container tasks, a location change task and a story. On average, the children per‐ formed best on the Sally-Bill task, 73% of the children passed this task. Despite this result and the careful adaptation of test methods, test methods were not found to be a factor influ‐ encing ToM development. Degree of visual impairment was also not found to be of influ‐ ence in developing a ToM, age was the only significant factor these authors found [36]. These are some interesting findings, firstly because they indicate that visually impaired peo‐ ple can show signs of having a ToM, secondly, because the question is raised where the dif‐ ference lies between visually impaired and sighted people. According to Minter et al. [35] tasks need to be adapted to the qualities of visually impaired but Peterson et al. [37] did not find a difference between tasks they used. Brambring and Ashbrock [38] elaborated on this question. They used a large variety of different tasks that did not require vision and found that performance was better than with traditional tasks but the blind children were on aver‐ age 19 months older when they were able to perform the same tasks as sighted children. A

more recent study [39] found that children with varying levels of congenital visual impair‐ ment when compared with sighted children matched on age and verbal intelligence, had a similar performance on advanced ToM stories (second order false belief, that is beliefs about beliefs) and non-literal stories. Despite a limited access to visual information during interac‐

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Peterson has not only studied ToM in visually impaired children, but also in deaf chil‐ dren [37, 40]. It looks as if deaf children are strongly delayed or even impaired in their ability to have a ToM. In their 1995 study, Peterson and Siegal tested the Sally-Anne paradigm on several deaf children who were able to communicate in sign language. Even though hearing children with or without intellectual disabilities can pass this task around a mental age of four, only 35% of these deaf children were able to pass at a mental age of 8. Furthermore, these results were similar to results of people with ASD, but worse than the performance of children with Down syndrome. Notwithstanding the lack of ToM, these deaf children were not autistic as they did not show any of the other characteristics of ASD [40]. According to Peterson and Siegel deaf children lack a ToM, because of the lack of understanding the communicative signals of others. It also appears that deaf children, especially those with hearing parents, communicate less at home than hearing children. On the one hand this is because a deaf child does not hear nor under‐ stand spoken language and on the other hand because their parents are not very fluent in sign language as an alternative for spoken language [41]. A direct consequence of the lower frequency of communication is that deaf children also communicate less about mental states, feelings and thoughts, which hinders the development of a ToM [37, 40]. This idea was supported in a more recent study that assessed the amount of communica‐ tion in play sessions for pairs of hearing mothers with their deaf children and compared them to hearing mothers with hearing children. They found that these signing mothers of deaf children do not necessarily communicate less than mothers of hearing children, but they do communicate less about mental states. Additionally, a relationship was found between the amount of communication about mental states of mothers of deaf children and the performance on false belief tasks of their children [42]. Despite the simi‐ lar way in which the lack of ToM expresses itself in people with ASD and in deaf, the cause is different. In children who are deaf it is often attributed to a lack of communica‐ tion about mental states, thoughts and feelings, whereas in ASD it is caused by inability

Another possibility for why hearing children outperform deaf children on ToM tasks could be that deaf children do have a ToM but only fail on certain aspects related to ToM and con‐ ventional tasks fail to test these aspects. Where normally false belief tests and variations of this are undertaken, a recent study addressed other aspects of ToM as well. Ketelaar, Rieffe, Wiefferink and Frijns [43] assessed deaf children that have received a cochlear implant (CI) at a young age, and compared them to hearing children. They tested other aspects of ToM than false belief, which are the understanding of other's intentions and others desires. The tasks were similar to false belief tasks, only instead of asking what someone would think or believe, it was asked what an other person intended to do with an object (after failing this

tions, children with congenital visual impairment can develop an effective ToM.

to take someone else's perspective.

more recent study [39] found that children with varying levels of congenital visual impair‐ ment when compared with sighted children matched on age and verbal intelligence, had a similar performance on advanced ToM stories (second order false belief, that is beliefs about beliefs) and non-literal stories. Despite a limited access to visual information during interac‐ tions, children with congenital visual impairment can develop an effective ToM.

Seeing things from a blind person's perspective is difficult when it comes to ToM tasks. Conventional ToM tasks have been carried out on people with impaired vision, showing that visually impaired children invariably performed worse than sighted children. McAl‐ pine and Moore did a false belief task using containers with unexpected contents and asked what another person would think was in it. Many of the blind children failed this task, even though sighted children are able to do this at a younger age [33, 34]. A similar study by Min‐ ter, Hobson and Bishop (1998) compared visually impaired with sighted children of the same verbal intelligence, and showed similar results. In their first experiment, they did a similar task as the container task McAlpine and Moore used. They used a warm teapot, fil‐ led with sand instead of tea. Whereas almost all sighted children were able to pass this task, almost half of the visually impaired children failed to answer false belief questions such as: "What did you think was in here?" and "What would he/she think is in here?" The authors note that blind people may have less experience with hot teapots because of the extra dan‐ ger their lack of vision provides. Their second experiment was done with three boxes, where the participants helped the experimenter hide a pencil for another experimenter and false belief questions were asked. Again, the visually impaired children performed worse than the sighted, but much better than on the previous task. The authors think this was because they were more involved in this task, because they helped with the hiding [35]. These find‐ ings show that children with visual impairments do worse on conventional ToM tasks than do their hearing peers. One could assume that blind children do not have a ToM, or develop it slower. However, other findings indicate that visually impaired children can pass a ToM task, given an adapted task. In line with the notion that things need to be seen more from a blind person's perspective, it could be possible that visually impaired people have just as much a ToM as sighted people do; it's only measured in the wrong way. Peterson and her colleagues confirmed this. They state that blind people may very well rely on completely different features of an object than sighted people do in order to decide what another person thinks about an object [36]. They tested if this was true by adapting frequently used false belief tasks. For example, they have changed the famous Sally-Anne task to a Sally-Bill task. In this task, there were no dolls or pictures of children with baskets and marbles, but it was a purely narrative story. The experimenters performed four ToM tasks, including similar tasks to the container tasks, a location change task and a story. On average, the children per‐ formed best on the Sally-Bill task, 73% of the children passed this task. Despite this result and the careful adaptation of test methods, test methods were not found to be a factor influ‐ encing ToM development. Degree of visual impairment was also not found to be of influ‐ ence in developing a ToM, age was the only significant factor these authors found [36]. These are some interesting findings, firstly because they indicate that visually impaired peo‐ ple can show signs of having a ToM, secondly, because the question is raised where the dif‐ ference lies between visually impaired and sighted people. According to Minter et al. [35] tasks need to be adapted to the qualities of visually impaired but Peterson et al. [37] did not find a difference between tasks they used. Brambring and Ashbrock [38] elaborated on this question. They used a large variety of different tasks that did not require vision and found that performance was better than with traditional tasks but the blind children were on aver‐ age 19 months older when they were able to perform the same tasks as sighted children. A

484 Recent Advances in Autism Spectrum Disorders - Volume I

Peterson has not only studied ToM in visually impaired children, but also in deaf chil‐ dren [37, 40]. It looks as if deaf children are strongly delayed or even impaired in their ability to have a ToM. In their 1995 study, Peterson and Siegal tested the Sally-Anne paradigm on several deaf children who were able to communicate in sign language. Even though hearing children with or without intellectual disabilities can pass this task around a mental age of four, only 35% of these deaf children were able to pass at a mental age of 8. Furthermore, these results were similar to results of people with ASD, but worse than the performance of children with Down syndrome. Notwithstanding the lack of ToM, these deaf children were not autistic as they did not show any of the other characteristics of ASD [40]. According to Peterson and Siegel deaf children lack a ToM, because of the lack of understanding the communicative signals of others. It also appears that deaf children, especially those with hearing parents, communicate less at home than hearing children. On the one hand this is because a deaf child does not hear nor under‐ stand spoken language and on the other hand because their parents are not very fluent in sign language as an alternative for spoken language [41]. A direct consequence of the lower frequency of communication is that deaf children also communicate less about mental states, feelings and thoughts, which hinders the development of a ToM [37, 40]. This idea was supported in a more recent study that assessed the amount of communica‐ tion in play sessions for pairs of hearing mothers with their deaf children and compared them to hearing mothers with hearing children. They found that these signing mothers of deaf children do not necessarily communicate less than mothers of hearing children, but they do communicate less about mental states. Additionally, a relationship was found between the amount of communication about mental states of mothers of deaf children and the performance on false belief tasks of their children [42]. Despite the simi‐ lar way in which the lack of ToM expresses itself in people with ASD and in deaf, the cause is different. In children who are deaf it is often attributed to a lack of communica‐ tion about mental states, thoughts and feelings, whereas in ASD it is caused by inability to take someone else's perspective.

Another possibility for why hearing children outperform deaf children on ToM tasks could be that deaf children do have a ToM but only fail on certain aspects related to ToM and con‐ ventional tasks fail to test these aspects. Where normally false belief tests and variations of this are undertaken, a recent study addressed other aspects of ToM as well. Ketelaar, Rieffe, Wiefferink and Frijns [43] assessed deaf children that have received a cochlear implant (CI) at a young age, and compared them to hearing children. They tested other aspects of ToM than false belief, which are the understanding of other's intentions and others desires. The tasks were similar to false belief tasks, only instead of asking what someone would think or believe, it was asked what an other person intended to do with an object (after failing this action) or what someone would want to eat (after showing them pictures of food they liked). It appeared that the deaf children and hearing children performed equally well on the inten‐ tion tasks, but the hearing children outperformed the deaf on false belief tasks and on the desire tasks [43].This study indicates that deaf children may possess some abilities related to a theory of mind. It should be noted, however, that this study only included children with a CI. These children thus had some hearing abilities, though different from hearing children. The study did not include a group that was completely deaf and so conclusions about com‐ pletely deaf children cannot be drawn.

**3.1. Making conversation**

language problems found in ASD.

autism lack the interest for this contact.

**3.2. Language**

or even awkward.

Language is something people use for communication, and so the willingness to communi‐ cate is related to their use of language [19].Despite possible technical problems in language the low desire for communication is one of the aspects of ASD that is mentioned in the DSM-IV-TR, that is not only problems in initiating and maintaining a conversation with oth‐ ers but also a lack of an internal willingness or desire to communicate [2]. If people with ASD are simply uninterested in communication, they will not put effort in initiating a social conversation spontaneously. This lack in willingness to communicate also contributes to the

Autism Spectrum Disorders in People with Sensory and Intellectual Disabilities – Symptom Overlap and Differentiating

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http://dx.doi.org/10.5772/53714

Initiating and maintaining a conversation can be difficult for people with sensory and intel‐ lectual disabilities too. The presence of others may go unnoticed for people with visual im‐ pairments, and communicative signs may be missed because of blindness or deafness. It has been found that deaf children communicate less with their hearing parents because of their poor skills in spoken language and their parents poor sign language skills [41]. In people with intellectual disabilities conversational skills may be worse than expected based on their chronological age, moreover, their initiations to communicate may be different, inadequate

Even though all of these impaired groups may show impaired conversation making skills, there are differences between autistic and non-autistic people. An example derived from a deaf population shows that despite other problems in the field of communication, such as monitoring a conversation and pragmatic use of language, non-autistic deaf children are not different from their hearing peers in initiating and maintaining a conversation [22]. But even though deaf children without ASD don't seem to have problems in initiating and maintain‐ ing a conversation, they still differ from their hearing peers in pragmatics and monitoring, hampering their conversational skills nevertheless. On the contrary, the impaired conversa‐ tional skills in autistic people lie in the area of the initiation and maintenance of a conversa‐ tion [2]. It also appeared that one of the areas in which the autistic and non-autistic children with deafblindness and profound intellectual disability differed significantly from each oth‐ er was the openness and willingness to take initiatives for contact [7]. It is evident that con‐ versation looks different for people with sensory or intellectual impairments versus people without impairments, and conversation skills are hampered by their lack of sensory and in‐ tellectual abilities. The difference with autistic people shows itself in the interest for this con‐ tact. Non-autistic sensory and/or intellectually impaired people still look for opportunities to make this contact or respond to other people's efforts to make contact, while people with

Besides a lower interest in communication than people without ASD, people with ASD show some technical language impairments as well. Some autistic people do not speak at all and in others the development of language can be seriously delayed or altered [19]. Further‐ more, it appears that joint attention and imitation behaviours, which are known to be im‐ paired in ASD, can predict language abilities [27], which raises the question whether

When children are completely deaf there is, however, still the possibility that, as seen in the visually impaired group, testing methods are not adequate for them. Peterson and Siegal [40] tried to make their intentions more clear in their false belief questions. They reasoned that someone with limited experience in conversation might expect that the experimenter just wants them to tell the location of Sally's marble, when they ask "Where will Sally look for her marble?" For this reason they altered the question to "Where will Sally first look for her marble?" By adding the word "first" they more clearly imply that they are looking for what sally thinks instead of where the marble really is. This slight alteration improved the deaf children's performance slightly, but not enough to overcome differences in ToM devel‐ opment [40] as the different tasks in the study by Ketalaar et al. [43] did. Peterson and Siegal only investigated false belief, though, whereas Ketelaar et al. adressesd other aspects of ToM and tested children with a CI who do have some hearing abilities, instead of children who are completely unable to hear. The question still remains whether a more appropriate meth‐ odology for deaf children could increase their scores on conventional ToM tasks and more research has to be done in order to clarify this.

Finally, people with intellectual disabilities often show ToM impairments as well. Typical developing children start to solve ToM tasks around the age of four to five years of age. A general characteristic of people with intellectual disabilities is that they have mental ages not corresponding to their chronological ages. If mental age is below five, which is the case in profoundly and severely intellectually disabled people, and sometimes also in moderately intellectually impaired people they will probably fail ToM tasks irrespective of their chrono‐ logical age [44]. Interpretations of ToM tasks should be done cautiously, when intellectually disabled people likely fail this task unrelated to the presence of ASD, to prevent unnecessa‐ ry suspicion of ASD.
