**2. Infancy**

Survey data provided by parents in the U.S. regarding their 2-, 5-, 8-, and 11-month-olds' experience with people over the course of one week demonstrated that the majority of their infant's time was spent interacting with adult females (2/3 of their time at 2 and 5 months of age and ¾ of their time at 8 and 11 months of age). Moreover, these infants also attended more to female than male faces during actual social interactions, thus augmenting their already greater experience with female than male faces [18]. Data collected from videos obtained via head-mounted cameras on 1- and 3-month-olds in Canada over the course of two weeks also showed that infants' exposure to faces was with females 70% of the time [19]. See **Figure 1**. This predominant exposure to female faces facilitates infants' ability to mentally represent female face exemplars and form summary representations of female faces, but hinders their ability to do the same with male faces [23–26]

To illustrate, 3-4-month-olds with a female primary caregiver were familiarized to eight different faces and then shown one of the familiarized faces paired with a novel face. They looked longer at the novel than familiar face when the faces were female, but showed no difference in looking when the faces were male, suggesting infants could recognize and discriminate between the female face exemplars, but not the male face exemplars [24]. Similarly,

Differential Trajectories in the Development of Attractiveness Biases Toward Female and Male Targets http://dx.doi.org/10.5772/intechopen.69342 127

females' health and reproductive value as compared to males' [1, 4], so attractiveness should be a more salient and valued attribute among women than men. In contrast to these theoretical viewpoints and adults and children's beliefs that physical appearance is more important for females than males [6–8], meta-analytic reviews of the attractiveness literature suggested there were no differences in how attractiveness affected individuals' ratings, impressions, and treatment of female and male targets [9–11]. It was noted, however, that studies including both female and male targets or comparisons between reactions to female and male targets were lacking, making it difficult to conclude whether there are truly differences in the impor-

In this chapter, we take a different theoretical approach to understanding the importance of attractiveness for female and male targets. Specifically, we discuss how cognitive representations for faces (i.e., how individuals mentally represent human faces) guide preferences for attractiveness. A seminal study demonstrated that adults perceive summary representations of faces (i.e., faces mathematically averaged together) as attractive [12]. Since its publication, empirical studies have supported the notion that facial *averageness* (the average value of the population of faces to which one is exposed) is attractive [13–16] and affectively rewarding [17]. Yet, early in development, infants and children have predominant experience with females [18–22], so the population to which they are exposed is more heavily weighted toward females than males, which impacts their cognitive representation of faces [23]. With changes in social experience and how individuals represent faces between infancy and adolescence, there are also developmental changes in the saliency of attractiveness for female and male targets. This chapter thus proposes a cognitive developmental perspective for understanding differential trajectories in the develop-

ment of children's attractiveness preferences and biases for female and male targets.

Survey data provided by parents in the U.S. regarding their 2-, 5-, 8-, and 11-month-olds' experience with people over the course of one week demonstrated that the majority of their infant's time was spent interacting with adult females (2/3 of their time at 2 and 5 months of age and ¾ of their time at 8 and 11 months of age). Moreover, these infants also attended more to female than male faces during actual social interactions, thus augmenting their already greater experience with female than male faces [18]. Data collected from videos obtained via head-mounted cameras on 1- and 3-month-olds in Canada over the course of two weeks also showed that infants' exposure to faces was with females 70% of the time [19]. See **Figure 1**. This predominant exposure to female faces facilitates infants' ability to mentally represent female face exemplars and form summary representations of female faces, but hinders their

To illustrate, 3-4-month-olds with a female primary caregiver were familiarized to eight different faces and then shown one of the familiarized faces paired with a novel face. They looked longer at the novel than familiar face when the faces were female, but showed no difference in looking when the faces were male, suggesting infants could recognize and discriminate between the female face exemplars, but not the male face exemplars [24]. Similarly,

tance of attractiveness for the two sexes [11].

ability to do the same with male faces [23–26]

**2. Infancy**

126 Perception of Beauty

**Figure 1.** The percentage of social interactions infants and toddlers have with female faces across the first three years. Percentages reflect data from Refs. [18, 19, 21].

10-, 14-, and 16-month-olds with a female primary caregiver who were familiarized to a video of a person speaking and then needed to locate an image of that person among three other distractor faces more easily located female than male faces. Caregiving experience seems to be important because same-aged infants with alternating experience with a female and male primary caregiver were equally successful at locating female and male faces in this task [27]. Results demonstrate predominant experience with female caregivers facilitates infants' ability to more easily represent and recognize female than male adult face exemplars, presumably due to their cognitive representation for human faces being weighted toward female adults.

Similar findings are evident among studies assessing infants' ability to summarily represent female and male faces. Six-month-olds were familiarized to eight different female faces and then saw three different face pairings: (1) an averaged female face (i.e., a face created by mathematically averaging the eight female faces) paired with a novel face; (2) an averaged female face paired with a familiar face; and (3) a familiar face paired with a novel face. If infants form summary representations of female faces, the averaged face should seem more familiar than the novel or familiar face even though they should recognize the familiar face. Indeed, infants looked more at the novel and familiar faces when each was paired with the averaged face, suggesting the averaged face was most familiar. They also looked more at the novel than familiar face when paired together, suggesting they did recognize the familiar face [25]. Infants' ability to summarily represent female faces is evident as early as 3 months of age [26] and might be present even earlier in development [28].

Additional studies using a paradigm similar to the one just described, but with male faces, showed no evidence of 6-month-olds' ability to summarily represent male faces. Manipulations to the paradigm, such as an increase in 6-month-olds' exposure to male faces through additional familiarization or testing of older infants (8-month-olds), still found that infants were unable to summarily represent male faces. Null results are difficult to interpret, but 11 different studies failed to provide evidence of infants' ability to mentally represent an average of the male faces to which they were exposed [23]. Taken together, the findings suggest most infants' initial representation for human faces is female-like (**Figure 2**).

Infants' ability to summarily represent female, but not male, faces is important because adults perceive summary (averaged) representations of faces as attractive [12, 14]. Thus, most infants' representation for human faces is not only female-like, but attractive. Faces most similar to this representation should be fluently processed and preferred [17, 23, 29]. Indeed, 6-montholds preferred to look more at an averaged female face relative to an unattractive female face when paired together. These results suggest that, like adults, they perceive averaged female faces as attractive [12, 25].

**Figure 2.** Using data from infants' average experience with faces across the first year [18], we created a simulation of a cognitive representation of faces weighted toward female-like. This morphed face includes 12 female and 7 male faces and was created so that female faces represent 70% of the morph and male faces represent 30% of the morph and thus mirrors most infants' typically greater facial experience with females than males [18, 19].

Although infants perceive averaged female faces as attractive, they do not necessarily prefer faces altered to be *more average* to those altered to be *less average*. To create such faces, researchers morph a face to be 50% closer to the averaged face or 50% further away from the averaged face. Despite these manipulations, 5- to 8-month-olds showed no overall differences in total looking toward the *more* and *less average* faces, although their longest look was toward the face made to be *less average* [30]. In another study with 12- to 24-month-olds, they looked more at the *less average* face than *more average* face [31]. Both sets of researchers suggested the less average faces might be particularly unusual or distinctive looking, thus drawing infant attention due to novelty rather than attractiveness. Even though faces were created to be *more average*, the 50% manipulation toward the averaged face might not have been sufficient to convey averageness (i.e., similarity to an averaged facial representation) and elicit a visual preference. Subsequently, as these researchers proposed, the 50% manipulation away from the average made faces appear atypical and elicited a novelty preference instead.

Additional studies using a paradigm similar to the one just described, but with male faces, showed no evidence of 6-month-olds' ability to summarily represent male faces. Manipulations to the paradigm, such as an increase in 6-month-olds' exposure to male faces through additional familiarization or testing of older infants (8-month-olds), still found that infants were unable to summarily represent male faces. Null results are difficult to interpret, but 11 different studies failed to provide evidence of infants' ability to mentally represent an average of the male faces to which they were exposed [23]. Taken together, the findings suggest most

Infants' ability to summarily represent female, but not male, faces is important because adults perceive summary (averaged) representations of faces as attractive [12, 14]. Thus, most infants' representation for human faces is not only female-like, but attractive. Faces most similar to this representation should be fluently processed and preferred [17, 23, 29]. Indeed, 6-montholds preferred to look more at an averaged female face relative to an unattractive female face when paired together. These results suggest that, like adults, they perceive averaged female

**Figure 2.** Using data from infants' average experience with faces across the first year [18], we created a simulation of a cognitive representation of faces weighted toward female-like. This morphed face includes 12 female and 7 male faces and was created so that female faces represent 70% of the morph and male faces represent 30% of the morph and thus

mirrors most infants' typically greater facial experience with females than males [18, 19].

infants' initial representation for human faces is female-like (**Figure 2**).

faces as attractive [12, 25].

128 Perception of Beauty

Taken together, studies suggest most infants' initial representation for human faces is weighted toward adult females and is attractive. Attractiveness should, therefore, be more salient among female than male faces. Attractiveness does seem to guide infants' visual interest in adult female faces, but does not consistently influence their interest in adult male faces. For example, across several studies, infants ranging in age from a few days old to 8 months looked longer at high attractive relative to low attractive female faces [32–35]. In two other studies that included both female and male face pairs, 3- to 6-month-olds showed a preference for the high attractive faces regardless of face pair gender—there were no effects or interactions involving stimulus gender [36, 37]. In another study, however, when the babyfaceness of the high and low attractive faces paired together was held constant, 4- to 6-month-olds showed a preference for high attractive female faces, but not for high attractive male faces [38]. Also, when 6- and 12-montholds saw pairs of male faces who differed in attractiveness, but were similar in masculinity, 6-month-olds showed no preference for high attractive males. The 12-month-olds, however, did show a visual preference for high attractive males, but only when the face pair was low masculine [39].

To summarize, when cues such as babyfaceness and masculinity are held constant within face pairs, young infants show no visual preference for attractive males [38, 39]. By the end of the first year, however, they visually prefer high attractive males, but within low masculine face pairs only. High attractive, low masculine males should be most similar to an attractive, female-like facial representation, so this similarity might cause infants to overgeneralize their visual preference for high attractive female faces to high attractive, low masculine male faces toward the end of the first year [39].

An attractive, female-like facial representation also seems to guide how infants categorize adult female and male faces. To test infant categorization, infants view several exemplars of faces from a particular category (e.g., low attractive females) and then see a novel exemplar from the familiarized category paired with a novel exemplar from a different category (e.g., a high attractive female). If they have formed a category, the novel exemplar from the familiarized category should seem more familiar than the novel exemplar from the novel category—thus, if infants are able to categorize the faces, they should look more at the novel category face than familiar category face even though both faces are novel to the infant.

Using this paradigm, infants show an ability to categorize adult female faces based on attractiveness by 6 months of age. They show this ability regardless of whether they are familiarized to low attractive or high attractive females. Importantly, 6-month-olds also showed an ability to discriminate between the category exemplars, demonstrating they individuated the female faces, but still grouped faces together based on attractiveness level [40]. In contrast, 12-montholds attend more to males' facial masculinity than attractiveness when categorizing adult male faces—they group together low masculine males and exclude high masculine males from the category. Low masculine males' perceptual similarity to the infants' female-like facial representation might be what facilitates infants' ability to categorize these faces by 12 months of age [39].

Attractiveness, therefore, seems to be a more salient cue when infants view female relative to male faces and it guides their visual preferences for and categorization of adult females, but not necessarily adult males. This early asymmetry is important to consider because how children functionally group people in their social world serves as a precursor to the development of biases and stereotypes [41]. Also, beyond the first year, toddlers continue to have predominant experience with females. Survey data provided by parents regarding their 18 to 36-month-olds' facial experience over the course of one week showed that approximately 68% of their toddlers' social interactions were with females (**Figure 1**) and they allocated a significantly greater percentage of time attending to female than male faces during these interactions [21]. Given the substantial brain growth that occurs during the first three years of life [42], these experiences likely not only maintain, but strengthen, children's attractive, female-like facial representation and greater attention toward females' than males' attractiveness. Such differential attention should subsequently influence categorization and person perception during early childhood.
