Article

Early androgens, activity levels and toy choices of children in the second year of life

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Abstract

The hypothesis that stronger preferences for active play styles contribute to stronger preferences for male-typical toys was examined in 47 boys and 37 girls at 19-months of age using ambulatory monitoring technology (i.e., actigraphy) to measure activity levels during contact with male-typical, female-typical, and gender-neutral toys. Digit ratios and salivary testosterone levels were measured earlier in children at 3-4months of age. There were no significant sex differences in digit ratios, salivary testosterone levels, or overall activity levels during toy play. In contrast, contact times showed large sex differences in infants' toy preferences. The within-sex comparisons showed that infant girls had significant preferences for female-typical toys over male-typical toys, whereas infant boys showed only a small preference for male-typical toys over female-typical toys. More male-typical digit ratios in early infancy predicted higher activity counts during toy play and less female-typical toy preferences in girls. However, in both sexes, activity levels were unrelated to toy preferences suggesting that factors other than activity level preferences contribute to the early emergence of gender-linked toy preferences.

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... Further, young monkeys reach for "gender-typical" toys (male: car, ball, wheeled toys; female: doll, pot, plush toys) more than toys that are typical for the other gender in humans, arguing for some biological rather than social basis for toy preferences (Alexander & Hines, 2002;Hassett, Siebert, & Wallen, 2008). Nineteen-month-olds with more "male-typical" digit ratios, which are linked to higher exposure to masculinizing hormones in the womb, are likely to be rated as having higher activity during play and show less "female-typical" toy preference (Alexander & Saenz, 2012). Once again, it has to be noted that not all studies on hormonal effects reveal congruent findings. ...
... Zosuls et al. (2009) reported infants' mild gender differences in play at 17 months, which increased at 21 months, and by 19 months, they observed spontaneous production of gender labels. At 18 and 19 months, male infants spend more time playing with cars and female infants with dolls when both toys are presented in the experiment, although they interact with these toys with equal frequency (Alexander & Saenz, 2012). Infants at this age seem to be aware of gender-specific toy preferences themselves, in that they link girl photographs with dolls and boy photographs with cars (Serbin, Poulin-Dubois, Colburne, Sen, & Eichstedt, 2001). ...
... A number of studies have argued that transitions in infant gender-related preferences occur between 14 and 21 months after birth during which self-awareness toward gender-specific toys also increases (Alexander & Saenz, 2012;Lauer & Yhang, 2016;Serbin et al., 2001;Zosuls et al., 2009). The previously reported developmental time window is in agreement with the outcomes of the current study, in which one of the main difference between male and female infants is that male infants around 15 months showed no preference for cars and dolls, unlike females who overall preferred dolls to cars. ...
Article
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In contrast to the anecdotal claim that “male infants like cars and female infants like dolls,” previous studies have reported mixed findings for gender‐related toy preferences in infancy. In Experiment 1, we explored the emergence of gender‐related preferences using face–car pairs (Experiment 1a, n = 51, 6–20 months) or face–stove pairs (Experiment 1b, n = 54, 6–20 months). In Experiment 2 (n = 42, 14–16 months), we explore the effect of toy properties, infants' past toy exposure, activity levels, and parental attitudes on such preferences using a wider range of toys. For both studies, infants demonstrated a general preference for faced stimuli over other objects, except for male infants who showed no preference between dolls and cars at around 15 months. Infants' prior experience participating in motor‐intensive activities, with wheeled toys and parental attitudes appeared to relate to female infants' preferences for dynamic toys. These results indicate a range of factors influence gendered toy preferences and suggest that nurture plays an important role.
... Children's interest in small vehicle toys may be influenced by what they learn from elder brothers at home and the type of cartoon show they watch on television. A study by Alexander and Saenz (2012), for instance, recorded that boys interest towards vehicle toys is possibly linked to the maturation of the brain system that supports both male or female selection of objects. In many occasions, boys engage in a more physically active game; throwing and pushing their small toy car on the railings or anywhere they can play around the walkways of the SC. ...
... Research has found that girls pay more attention to soft animal toys and princess dolls when browsing in a store. Naturally, playing dolls and soft toys animals are significant to girls and is claimed to be a pure framework for their preference of entertainment since early childhood (Alexander and Saenz, 2012;Ironico, 2012). Girls also prefer these cute toys as they are not aggressive to play with, and promote conversation oriented play like role-playing (Kail and Cavanaugh, 2017). ...
Thesis
Shopping centres are no doubt one of the many modern-day necessities, providing everything one might need all under one roof. To encourage customer visits, prolong time spent, and potential purchases, the environment of a shopping centre is often designed in a specific way to affect customer’s shopping values, enticing both their emotional and physiological sensations. A well designed shopping centre is a combination of modern architecture, as well as the integration of the right shopping atmospheric variables such as wall decoration, lighting, sound effects, music as well as retail layout. In today’s society, parents and children visit shopping centres for multiple purposes including retail therapy, entertainment, socialising and many others. Most of the time, parents intend to complete a purchase and at the same time to enjoy the hedonic aspects of the shopping environment with their children. In the shopping journey between a parent and their accompanying child, children play a significant role in determining the family’s shopping expenses, one that is as important as an adult. However, research within this area also found that having a child companion can reduce positive shopping values due to the child’s behaviour. As a result, this will lead parents into making hasteful decisions such as shortening their shopping visit or even making a turning back home. Although numerous efforts have been made by scholars to understand the effects of shopping atmospheric variables on the customer, only a few research is conducted to understand how these variables affect small children’s emotional response and shopping behaviour during their shopping journey. Therefore, this research focuses on ‘how to improve children aged between three to seven years shopping experience through the shopping atmospheric variables when accompanying parents during shopping activities?’. The qualitative methodology using ethnography studies is employed in this research to develop an in-depth understanding of children customer shopping experience. Research data is collected using ethnography cultural probes (children shopping experience diary), digital ethnography observations and face-to-face semi-structured interviews. Results from this study are used to help the researcher develop a theoretical framework to identify atmospheric variables that are salient to young children customers, which may later provide vital insights in improving their shopping journey. Based from the findings, this research found that children emotional response, shopping behaviour and experience are influenced by four key factors. Each key factor explained how children react towards shopping atmospherics variables they engaged with, including their self-role and characteristics as a young customer, in-store decorative elements and electronic devices, categories for merchandise and snacks and other human variables while shopping with parents. The findings help to clarify children’s attitude towards each shopping atmospherics variable, and factors that might potentially influence their response towards them. To continue, the findings also highlighted important insights that will be useful for the shopping centre’s managerial team, designer and retailer who aim to improve children’s shopping experience. The improvement made based on these insights may also potentially help businesses create a more pleasant shopping environment for children as well as increase store and brand loyalty. Moreover, the findings may also benefit parents, since a positive children’s shopping behaviour may contribute towards a more positive family’s shopping vibes.
... Experimental studies with mammals reveal that lower 2D:4D results from stronger masculinization and defeminization prenatal processes (i.e., exposure to higher levels of prenatal testosterone relative to estrogen; Zheng & Cohn, 2011). For instance, girls with low 2D:4D show less preference for female-typical toys (e.g., baby dolls) and are more active during play (Alexander & Saenz, 2012), whereas boys show more preference for male-type plays (e.g., play-fighting, ball games) (Hönekopp & Thierfelder, 2009). Women with low 2D:4D tend to identify with male-type sex roles (Csathó et al., 2003), whereas men tend to be more dominating (Meij, Almela, Buunk, Dubbs, & Salvador, 2012) risk-taking (Stenstrom, Saad, Nepomuceno, & Mendenhall, 2011), and sensation-seeking (Fink, Neave, Laughton, & Manning, 2006). ...
... This might suggest that despite women expecting more benefits from the intervention (the effect of sex), there might have been a higher occurrence of depressed individuals among more feminized participants (the effect of 2D:4D). Second, individuals with low 2D:4D tend to be more energetic and willing to risk more (Alexander & Saenz, 2012;Fink et al., 2006;Meij et al., 2012;Stenstrom et al., 2011). These individuals may be more likely to try and enjoy new activities such as the proposed gratitude intervention. ...
Article
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Men are less grateful than women and less likely to intentionally enhance gratitude via interventions. Yet, little is known if sex differences in gratitude result from biological influences such as prenatal testosterone and estrogen levels – hormones that control the development of sex-specific characteristics. In two studies, we examined how sex and second-to-fourth digit ratio (2D:4D) – an indicator of prenatal sex hormones exposure – predicts gratitude intervention use. In the first study, we tested whether lower 2D:4D (i.e., higher masculinization) would suppress gratitude intervention use. Contrary to expectations, after controlling for sex, women and men with more male-type fingers were more motivated and likely to complete the intervention. In the second study, we replicated these findings using a larger sample and different 2D:4D metric. Our research suggests that motivation towards gratitude interventions is facilitated by female sex and masculinity. These findings provide initial evidence for the biological grounding of individual differences in gratitude behavior.
... At 6 months, although both boys and girls show a visual preferencefordollsovertrucks,boyslookedlongerattrucksthandid girls (Alexander, Wilcox, & Woods, 2009;Woods, Wilcox, Armstrong, & Alexander, 2010). These looking time differences continuethrough infancy intotoddlerhood (Jadva, Hines, &Golombok, 2010).Inthefirst2 yearsoflife,girlsspendmoreplaytimewithfeminine toys than do boys and boys spend more play time with masculine toys than do girls (Alexander & Saenz, 2012;Servin, Bohlin, & Berlin, 1999). During preschool, boys increased their play with masculine toys and decreased dramatically their play with feminine toys, whereas girls' play preferences changed little (Davis & Hines, 2015). ...
... Similarly, research indicates that boy infants visually attend to trucks even though the vehicle was not in motion, and potentially before the infant had the physical development to play with the truck via propulsion (Alexander etal.,2009;Woods etal., 2010).Additionally, genderdifferences in activity levels do not relate to children's early toy choices as one would expect if boys preferred propulsion-based play (Alexander & Saenz, 2012). Further, the current results differ from results of nonhumanprimateresearch,afoundationforthehypothesesthatgendertyped toy preferences reflect hormonally influenced behavioral and cognitive biases (Hassett et al., 2008). ...
Article
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Children’s toy play is at the foundation of child development. However, gender differentiation in early play experiences may result in gender differences in cognitive abilities, social interactions, and vocational choices. We investigated gender-typing of toys and toys’ propulsive properties (e.g., wheels, forward motion) as possible factors impacting children’s toy interests, perceptions of other children’s interests, and children’s actual toy choices during free play. In Studies 1 and 2, 82 preschool children (42 boys, 40 girls; mean age = 4.90 years) were asked to report their interest and perceptions of other children’s interests in toys. In Study 1, masculine, feminine, and neutral toys with and without propulsive properties were presented. Children reported greater interest in gender-typed toys and neutral toys compared to cross-gender-typed toys. In Study 2, unfamiliar, neutral toys with and without propulsive properties were presented. Propulsive properties did not affect children’s interest across both studies. Study 3 was an observational study that assessed toy preferences among 42 preschool children (21 males, 21 females, mean age = 4.49 years) during a play session with masculine, feminine, and neutral toys with and without propulsive properties. Gender-typed toy preferences were less apparent than expected, with children showing high interest in neutral toys, and girls playing with a wide variety of masculine, feminine, and neutral toys. Gender differences in interest for toys with propulsion properties were not evident. Overall, gender differences in children’s interest in toys as a function of propulsion properties were not found in the three experiments within this study.
... Studies in our review appeared to treat the gender categorization of toys as uncontroversial, even though, according to our review, it was not uncommon for toys to be assigned to different gender categories in different studies. For example, in some studies, blocks were classified as boy-related toys (e.g., Alexander & Saenz, 2012;Benenson et al., 1997;Fagot & Patterson, 1969), and in other studies they were classified as neutral toys (e.g., Cherney et al., 2003;Guinn, 1984;Wood, Desmarais, & Gugula, 2002). Similarly, drawing toys were sometimes categorized as girl-related toys (e.g., Berenbaum & Hines, 1992;Martin et al., 2013), and sometimes as neutral toys (e.g., Berenbaum & Snyder, 1995;Pasterski et al., 2005); and stuffed toys were equally likely to be classified as girl-related toys (e.g., DeLucia, 1963;Jacklin et al., 1973) as neutral toys (e.g., Alexander & Saenz, 2012;Idle et al., 1993;Moller & Serbin, 1996), but were also sometimes classified as boy-related toys (e.g., Stagnitti, Rodger, & Clarke, 1997). ...
... For example, in some studies, blocks were classified as boy-related toys (e.g., Alexander & Saenz, 2012;Benenson et al., 1997;Fagot & Patterson, 1969), and in other studies they were classified as neutral toys (e.g., Cherney et al., 2003;Guinn, 1984;Wood, Desmarais, & Gugula, 2002). Similarly, drawing toys were sometimes categorized as girl-related toys (e.g., Berenbaum & Hines, 1992;Martin et al., 2013), and sometimes as neutral toys (e.g., Berenbaum & Snyder, 1995;Pasterski et al., 2005); and stuffed toys were equally likely to be classified as girl-related toys (e.g., DeLucia, 1963;Jacklin et al., 1973) as neutral toys (e.g., Alexander & Saenz, 2012;Idle et al., 1993;Moller & Serbin, 1996), but were also sometimes classified as boy-related toys (e.g., Stagnitti, Rodger, & Clarke, 1997). This pattern suggests that researchers sometimes disagree on what toys are boy-related, girl-related, or neutral. ...
Article
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It is generally recognized that there are gender-related differences in children’s toy preferences. However, the magnitude of these differences has not been firmly established. Furthermore, not all studies of gender-related toy preferences find significant gender differences. These inconsistent findings could result from using different toys or methods to measure toy preferences or from studying children of different ages. Our systematic review and meta-analysis combined 113 effect sizes from 75 studies to estimate the magnitude of gender-related differences in toy preferences. We also assessed the impact of using different toys or methods to assess these differences, as well as the effect of age on gender-related toy preferences. Boys preferred boy-related toys more than girls did, and girls preferred girl-related toys more than boys did. These differences were large (d ≥ 1.60). Girls also preferred toys that researchers classified as neutral more than boys did (d = 0.29). Preferences for gender-typical over gender-atypical toys were also large and significant (d ≥ 1.20), and girls and boys showed gender-related differences of similar magnitude. When only dolls and vehicles were considered, within-sex differences were even larger and of comparable size for boys and girls. Researchers sometimes misclassified toys, perhaps contributing to an apparent gender difference in preference for neutral toys. Forced choice methods produced larger gender-related differences than other methods, and gender-related differences increased with age.
... Previous research has indicated that even young infants and toddlers demonstrate gender-typed toy preferences. However, the results of these studies are mixed and discrepancies exist in the age at which these preferences are shown to first arise (Alexander et al. 2009;Alexander and Saenz 2012;Campbell et al. 2000;Lamminmåki et al. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11199-017-0858-4) ...
... However, Alexander et al. (2009) and Todd et al. (2016) found gender-typed preferences in both male and female infants at 9 months of age. Other literature indicates that these preferences are demonstrated by toddlers older than 12 months (Alexander and Saenz 2012;Lamminmåki et al. 2012;Servin et al. 1999;van de Beek et al. 2009). Given that there is discrepancy in the age at which gender-typed toy preferences first arise, further research is needed to examine when these preferences develop. ...
Article
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Gender socialization influences children at early ages, shaping their developing identities. The toys provided by parents deliver some of the earliest gender-based messages by encouraging children to engage in activities associated with, for example, dolls and trucks. In the current study, we measured the influence of parental socialization by assessing 5- and 12 ½-month-old infants’ exposure to dolls and trucks and by experimentally manipulating parents’ encouragement to play with these toys. We found that infants displayed gender-typical toy preferences at 12 ½, but not 5 months, a pattern characteristic of previous studies. However, brief encouragement by a parent to play with toys from each category was ineffective in altering infants’ preferences. Rather, the types of toys present in the home predicted preferences, suggesting that at-home exposure to toys may be influential in the development of toy preferences. These findings reveal that socialization processes may indeed play a role in the formation of early gender-typical toy preferences and highlight the importance of equal toy exposure during infancy to ensure optimal development.
... Based on the same cohort, a correlation of the obtained salivary testosterone values (EIA) at the age of 3-4.9 months with play behavior and eye-contact time at the age of 19 months was analyzed. It was observed that there was no influence of salivary testosterone levels during minipuberty on gender-linked play behavior [58] or eye-contact time [59] in young children of either sex. ...
Article
Hormonal 'minipuberty' refers to a transient sex specific surge of LH, FSH, testosterone (T) and estradiol (E2) in the first few months of life. We hypothesized a potential long term effect of this hormonal surge on somatic parameters in the following years and therefore designed this longitudinal study. A hierarchical multiple regression analysis was used to analyze the potential influence of hormone concentrations during minipuberty on anthropometric measurements conducted in the first six years of life. Thirty-five healthy babies (17 male, 18 female) were the participants. Testosterone, E2, SHBG, LH and FSH were measured at the ages of four, eight and 20 weeks. Anthropometric measurements were taken eight times in the first 12 months, then every six months up to the age of six years. A significant negative effect was found in boys between testosterone and LH levels at eight weeks and body weight up to the age of six years and BMI up to six years (LH) and three years (T), respectively. A further negative effect was found between E2 levels at the age of 20 weeks and body weight as well as body length in the years that followed. A positive effect was observed between E2 at the age of four weeks and skin fold thickness up to the age of six years in boys. No significant effects were found in girls. The findings seem to reflect an up to now unknown long-term influence of the physiological early hormonal surge on the subsequent male but not female somatic development. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
... Participants included 47 children (29 males and 18 females) who took part in a longitudinal study investigating sex-linked behavior. For more information on the sample, please refer to the following articles (30)(31)(32)(33)(34)(35). Signed informed consent was obtained from all parents prior to participation in the study. ...
Article
Full-text available
Despite strong evidence linking sleep to developmental outcomes, the longitudinal relationship between sleep and emotional wellbeing remains largely unknown. To address this gap in our knowledge, the current study examined sleep in infancy, measured via actigraphy, as a predictor of social-emotional problems in toddlers. A total of 47 children (29 males) were included in this longitudinal study. At time one, actigraphy measures of sleep were obtained from 3- to 4-month-old infants. At time two, parents rated their 18- to 24-month-old toddler’s social-emotional wellbeing using the Brief Infant Toddler Social Emotional Assessment. Results indicated that boys tended to have higher levels of externalizing behaviors than did girls. Additionally, boys with longer sleep durations also showed lower sleep efficiency. In girls, sleep duration in infancy was a significant predictor of Autism Spectrum Disorder behaviors and approached significance as a predictor of externalizing problems in toddlerhood. Our findings are the first to show a relationship between sleep measured in infancy and Autism Spectrum Disorder symptomatology measured in early childhood. They suggest that the etiology of social-emotional problems may differ between genders and raise the possibility that sleep/wake cycles may be differentially related to Autism Spectrum Disorder symptoms in girls and boys.
... These background assumptions, in turn, have shaped the dominant methodology in this area of research. For example, researchers have not attempted to categorize or create toys on the basis of the presence or absence of features or affordances explicitly theorized to be timelessly or universally appealing to a masculinized brain (Fine 2015), such as movement, color, and form (Alexander 2003), affordance for active play (Alexander and Saenz 2012), or stimuli that involve rule-driven input-function-output systems versus objects that allow for empathizing activities (Baron-Cohen 2003). Instead, they construct masculine, feminine, and gender-neutral categories on the basis of their assumed or observed popularity with girls and boys in a particular time and place (Bleier 1984). ...
Article
Investigations of sex differences in the human brain take place on politically sensitive terrain. While some scholars express concern that gendered biases and stereotypes remain embedded in scientific research, others are alarmed about the politicization of science. To help better understand these debates, this review sets out three kinds of conflicts that can arise in the neuroscience of sex differences: academic freedom versus gender equality; frameworks, background assumptions, and dominant methodologies; and inductive risk and social values. The boundaries between fair criticism and politicization are explored for each kind of conflict, pointing to ways in which the academic community can facilitate fair criticism while protecting against politicization.
... Sex differences in toy preference have been found amongst 12-14-month-old infants in 'play alone' conditions (Lamminmäki et al., 2012;Servin et al., 1999;van de Beek et al., 2009), yet parents were often present in the same room, sometimes sitting close by. Where 'play alone' and 'play with parent' conditions have been incorporated into the same study, results are not always consistent; Alexander and Saenz (2012) found stable sex differences across such conditions at 19 months, whereas Zosuls et al. (2009) found stereotyped preferences were generally weaker when infants aged 17 and 21 months played with their mother than when playing alone. Findings may vary by cultural context and sex of the play partner (Servin et al., 1999), and parental behaviour in the research context may not always represent their typical behaviour at home. ...
Article
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Many studies have found that a majority of boys and girls prefer to play with toys that are typed to their own gender but there is still uncertainty about the age at which such sex differences first appear, and under what conditions. Applying a standardized research protocol and using a selection of gender-typed toys, we observed the toy preferences of boys and girls engaged in independent play in UK nurseries, without the presence of a parent. The 101 boys and girls fell into three age groups: 9 to 17months, when infants can first demonstrate toy preferences in independent play (N=40); 18 to 23months, when critical advances in gender knowledge occur (N=29); and 24 to 32months, when knowledge becomes further established (N=32). Stereotypical toy preferences were found for boys and girls in each of the age groups, demonstrating that sex differences in toy preference appear early in development. Both boys and girls showed a trend for an increasing preference with age for toys stereotyped for boys. Theoretical implications of the findings are discussed with regard to biological predispositions, cognitive development and environmental influences on toy preference.
... In other research measuring visual attention, female infants compared to male infants look longer at a doll than a toy truck (Alexander et al., 2009;Lauer et al., 2015). Later, boys prefer interacting with toy vehicles and girls prefer interacting with dolls (for discussion, see Alexander and Saenz, 2012). Although gender-linked toys (e.g., vehicles, baby dolls) are clearly cultural artifacts associated with contemporary social roles for men and women (Liben and Bigler, 2002), nonhuman primates also show similar sex differences in response to these gender-linked objects (Alexander and Hines, 2002;Hassett et al., 2008). ...
Article
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Adolescents and adults show preferences for male and female body shapes consistent with evolutionary theories of reproductive fitness and mate selection. However, when these preferences for females with narrow waists (i.e., 0.7 waist-to-hip ratio) and men with broad shoulders (i.e., mesomorphic body shape) emerge during the lifespan is largely unknown. To address this knowledge gap, eye-movements were tracked in 144 infants (3 to 18 months of age) during computer presentation of three-dimensional human figures varying in body features thought relevant for reproductive success (e.g., secondary sex characteristics, waist-to-hip ratio). When presented with pairs of figures differing in apparent sex, male and female infants looked significantly longer at the female figure compared to the male figure, a new finding that extends previous research showing preferences for female faces in infancy. When presented with same-sex figures differing in characteristics associated with mate value, male and female infants looked longer at a low mate value male (i.e., an endomorphic body type) compared to a high mate value male (i.e., a mesomorphic body type), a finding that replicates the results of previous research. In addition, the novel use of high and low mate value female figures showed a sex difference in visual attention, such that female infants looked longer at the high mate value female figure compared to the low mate female figure whereas male infants showed the opposite pattern of results. In sum, these findings suggest that infants generally do not possess preferences for adult-defined attractive male body shapes. However, infant girls’ greater attention to a female figure with an adult-preferred waist-to-hip ratio raises the possibility that evolved preferences for 0.7 waist-to-hip ratio influence girls’ later preference for toys representing females with an hourglass shape, perhaps supporting elaboration of adult social behaviors that enhance reproductive success (e.g., cooperative breeding).
... According to Maccoby, gender serves as an organizational principle for children, helping them to understand and interpret the behaviour of those around them. A further study by Alexander and Saenz (2012) found that 2-year-old girls preferred toys typically associated with girls over those associated with boys, but then 2-year-old boys showed only a slight preference for male children's toys over female ones. These findings support the idea that toy preferences, although based on gender, are not a perfect indication of gender identity. ...
Book
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In this volume, we examine the relationship between gender and education with respect to the Italian context. The purpose is to forge a space for a progressively varied and dense area of interdisciplinary research on gender and education. As new gender studies fields are rapidly developing and becoming pivotal in the traditional social disciplines of sociology, educational studies, pedagogy, anthropology, we felt a greater need for a dynamic and intersectional examination that plots emerging definitions and debates while uncovering the critical complexities of gender and education in Italy. These include issues relating to: - the influence that family socialization and pre-school education have on both the formation of gender identities and the development of educational paths; - the female hegemony in the demography of the teaching staff and the repercussions of this numerical dominance for both male and female colleagues and students in terms of patterns and methodologies; - the reproduction of women and men’s traditional choices in fields of study such as STEM in the tracks of the Italian secondary education and university system; the barriers to a gender neutral vision of university career choices; the influence of parents’ educational attainment – especially that of mothers – on the educational achievements of younger men and women over time; - the growing importance of learning IT and digital skills for employability - especially for women; - the efficacy of experiments in coding, robotics and computational learning as part of innovative programs for pupils; - gender gaps in financial literacy and gender divides in more complex financial skills; - the social construction of gender categories in standardized assessments of adolescents’ competences. In adopting a critical approach to gender and education as the complex intertwining of these crucial issues, we recognize the importance of probing beyond the boundaries of specific domains in order to develop a more intersectional focus.
... Rather than describing children as cognitive processors of direct and vicarious learning and reinforcement experiences (Bussey & Bandura, 1999), self-socialization theories of gender development emphasize that children are distinctly motivated to understand their social worlds; children seek to determine which attributes are associated with which gender groups, and build gender identities based on this information. While self-socialization theories might be seen as particularly separate from biologically based approaches, which emphasize how factors that govern sexual differentiation in the body (i.e., hormones, genes) also influence sexual differentiation in behavior (e.g., Alexander & Saenz, 2012;Berenbaum, 1999;Wallen, 2005), researchers from both perspectives have been greatly interested in gender differentiation in infancy and early childhood (e.g., Alexander & Wilcox, 2012;Zosuls et al., 2009). Early differences linked to biological sex are seen as a way of assessing the extent to which sexually dimorphic behaviors exist before more extensive social experience. ...
Article
This article advances a self-socialization perspective demonstrating that children's understanding of both gender categories represents an intergroup cognition that is foundational to the development of gender-stereotyped play. Children's (N = 212) gender category knowledge was assessed at 24 months and play was observed at 24 and 36 months. Higher levels of gender category knowledge and, more specifically, passing multiple measures of knowledge of both gender categories at 24 months was related to increases in play over time with gender-stereotyped toys (doll, truck), but not gender-stereotyped forms of play (nurturing, motion). In contrast to the long-standing focus on self-labeling, findings indicate the importance of intergroup cognitions in self-socialization processes and demonstrate the generalizability of these processes to a diverse sample.
... Evidence of any organizational effects of postnatal T on behavior, however, requires establishing associations between postnatal concentrations of T and behavioral outcomes beyond the infantile period of transient HPG activation. For that reason, we tested whether postnatal T concentrations measured at 3-4 months of age would predict gender-typical play behavior and activity levels in children in the second year of life (60). Play preferences were videotaped and children's interactions with male-typical, femaletypical, and gender-neutral toys were coded later using behavioral coding software (Noldus Observer XT). ...
Article
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Converging evidence from over 40 years of behavioral research indicates that higher testicular androgens in prenatal life and at puberty contribute to the masculinization of human behavior. However, the behavioral significance of the transient activation of the hypothalamic-pituitary-gonadal (HPG) axis in early postnatal life remains largely unknown. Although early research on non-human primates indicated that suppression of the postnatal surge in testicular androgens had no measurable effects on the later expression of the male behavioral phenotype, recent research from our laboratory suggests that postnatal testosterone concentrations influence male infant preferences for larger social groups and temperament characteristics associated with the later development of aggression. In later assessment of gender-linked behavior in the second year of life, concentrations of testosterone at 3-4 months of age were unrelated to toy choices and activity levels during toy play. However, higher concentrations of testosterone predicted less vocalization in toddlers and higher parental ratings on an established screening measure for autism spectrum disorder. These findings suggest a role of the transient activation of the HPG axis in the development of typical and atypical male social relations and suggest that it may be useful in future research on the exaggerated rise in testosterone secretion in preterm infants or exposure to hormone disruptors in early postnatal life to include assessment of gender-relevant behavioral outcomes, including childhood disorders with sex-biased prevalence rates.
... This feature is important because it would allow sufficient time for the testosterone to have exerted organisational influences on the brain and behaviour, meaning that the observations made could not be attributable to transient (i.e., activational) effects of the hormone. Findings from studies that utilised saliva samples, on the other hand, have generally been equivocal (Alexander & Saenz, 2012;Alexander et al., 2009). It is therefore relevant to note that these, and some other studies (Alexander & Saenz, 2011Auyeung et al., 2012;Corpuz, 2021) that obtained saliva samples at approximately 3-6 months did not observe a significant sex difference for testosterone. ...
Article
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Sexually differentiated behaviour appears to emerge from a complex interaction of biological and socio-cultural factors, with prenatal exposure to steroid hormones such as testosterone thought to play a key role. Due to large sex differences being present from a very early age, much research has focussed on the influence these hormones may have on play preferences during childhood. We present an overview of the literature and a random-effects meta-analysis linking amniotic testosterone with sexually differentiated play preferences (k = 9, n = 493). The overall effect size estimate was in the theory-consistent direction (i.e., with higher levels of testosterone associated with more male-typical play preferences), though not statistically significant (r = 0.082, p = 0.274). However, after three hypothesised missing studies were imputed via the trim and fill procedure , a significant correlation emerged (r = 0.166, p = 0.014). Nevertheless, one sample was observed to exert a particularly large influence on the outcome of the analysis. Notably this was the second biggest sample and related to the largest effect size estimate. Though far from conclusive, the overall findings are consistent with the idea that individual differences in prenatal testosterone within the typical range predict sexually differentiated play preferences in early life. However, these effects may be small in magnitude and appear to vary considerably across studies.
... Of the included studies that compare infants across conditions in which the same participant plays (a) alone and (b) in interaction with a parent, findings are inconsistent. One study found stable sex differences across play-alone and playwith parent conditions (Alexander & Saenz, 2012), whereas others found that infants played with gender-typed toys less when with their mother than when alone (Zosuls et al., 2009) and more with male-typed toys when with their father than when alone (Servin et al., 1999). In studies involving older children, no differences were found between play-alone or play-with-parent conditions for 3-5-year-olds (Servin et al., 1999) but typically developing 3-10- ...
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From an early age, most children choose to play with toys typed to their own gender. In order to identify variables that predict toy preference, we conducted a meta-analysis of observational studies of the free selection of toys by boys and girls aged between 1 and 8 years. From an initial pool of 1788 papers, 16 studies (787 boys and 813 girls) met our inclusion criteria. We found that boys played with male-typed toys more than girls did (Cohen's d = 1.03, p < .0001) and girls played with female-typed toys more than boys did (Cohen's d = −0.91, p < .0001). Meta-regression showed no significant effect of presence of an adult, study context, geographical location of the study, publication date, child's age, or the inclusion of gender-neutral toys. However, further analysis of data for boys and girls separately revealed that older boys played more with male-typed toys relative to female-typed toys than did younger boys (β = .68, p < .0001). Additionally, an effect of the length of time since study publication was found: girls played more with female-typed toys in earlier studies than in later studies (β = .70, p < .0001), whereas boys played more with male-typed toys (β = .46, p < .05) in earlier studies than in more recent studies. Boys also played with male-typed toys less when observed in the home than in a laboratory (β = −.46, p < .05). Findings are discussed in terms of possible contributions of environmental influences and age-related changes in boys' and girls' toy preferences.
... Sex differences in toy preference have been found amongst 12-14-month-old infants in 'play alone' conditions (Lamminmäki et al., 2012;Servin et al., 1999;van de Beek et al., 2009), yet parents were often present in the same room, sometimes sitting close by. Where 'play alone' and 'play with parent' conditions have been incorporated into the same study, results are not always consistent; Alexander and Saenz (2012) found stable sex differences across such conditions at 19 months, whereas Zosuls et al. (2009) found stereotyped preferences were generally weaker when infants aged 17 and 21 months played with their mother than when playing alone. Findings may vary by cultural context and sex of the play partner (Servin et al., 1999), and parental behaviour in the research context may not always represent their typical behaviour at home. ...
Article
Many studies have found that a majority of boys and girls prefer to play with toys that are typed to their own gender but there is still uncertainty about the age at which such sex differences first appear, and under what conditions. Applying a standardized research protocol and using a selection of gender-typed toys, we observed the toy preferences of boys and girls engaged in independent play in UK nurseries, without the presence of a parent. The 101 boys and girls fell into three age groups: 9 to 17 months, when infants can first demonstrate toy preferences in independent play (N = 40); 18 to 23 months, when critical advances in gender knowledge occur (N = 29); and 24 to 32 months, when knowledge becomes further established (N = 32). Stereotypical toy preferences were found for boys and girls in each of the age groups, demonstrating that sex differences in toy preference appear early in development. Both boys and girls showed a trend for an increasing preference with age for toys stereotyped for boys. Theoretical implications of the findings are discussed with regard to biological predispositions, cognitive development and environmental influences on toy preference.
... So, although numerous findings on the relation between 2D:4D and behavior-related correlates exist [Manning 2002], some questions on the nature of the mechanism behind this relation remain unanswered. It can be speculated that PT not directly influences the development of cognitive abilities but that it only shapes certain preferences, such as regarding playing behavior [Alexander, Saenz 2012, Beltz et al. 2013, Berenbaum, Beltz 2011, Ceci et al. 2009, see also Berenbaum et al. 2012, Valla, Ceci 2011]. These preferences might then have training effects in the respective cognitive and/ or developmental dimensions [Ceci et al. 2009, Valla, Ceci 2011]. ...
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The role of prenatal testosterone (PT) in human behavior has increasingly been in the scope of psychoneuroendocrinological research in the recent years and has also been used to explain features of child (language) development. PT can be assessed by means of the so-called digit ratio 2D:4D, which is the ratio between the index (2nd digit) and the ring finger (4th digit). In the current paper, relations between PT, operationalized by means of 2D:4D, on the one hand and language development and media preferences (use of picture books) on the other hand in a sample of 190 three to four year-old children are reported. PT was significantly negatively associated with male as well as female performances in several language tests (e.g., language comprehension skills). In two analyses, 2D:4D was able to significantly distinguish between children of different developmental stages (normal vs. needing support vs. delayed). It was also found that, by trend, higher PT might be associated with less proneness to use picture books. It is concluded that PT is negatively associated with some features of language development as well as, potentially, with some early media preferences in preschool age. Theoretical models of explanation and practical implications are discussed.
... In humans, Smilansky cognitive play categories include functional (using toys), constructive (creating materials), or dramatic (transforming/imagining objects) play (181). As in rodents, there are also sex differences in human play that are demonstrated in terms of toy preference (e.g., cars vs dolls) (182,183), general activity levels in infants less than a year old (184), and the performance of rough and tumble play (185). Masculine play indices in children 14 months, 3.5 years, and 8 years old are positively correlated with concentrations of testosterone in infant urine at 6 months, in maternal blood at 16 weeks' gestation, and in amniotic fluid at 16 weeks gestation, respectively (133,(186)(187)(188). ...
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Postnatal development includes dramatic changes in gonadal hormones and the many social behaviors they help regulate, both in rodents and humans. Parental care-seeking is the most salient social interaction in neonates and infants, play and pro-social behaviors are commonly studied in juveniles, and the development of aggression and sexual behavior begins in peripubertal stages but continues through late adolescence into adulthood. While parental behaviors are shown after reproductive success in adulthood, alloparenting behaviors are actually high in juveniles as well. These behaviors are sensitive to both early life organizational effects of gonadal hormones and later life activational regulation. However, changes in circulating gonadal hormones and the display of the above behaviors over development differs between rats, mice and humans. These endpoints are of interest to endocrinologist, toxicologists, neuroscientists because of their relevance to mental health disorders and their vulnerability to effects of endocrine disrupting chemical exposure. As such, the goal of this minireview is to succinctly describe and relate the postnatal development of gonadal hormones and social behaviors to each other, over time and across animal models. Ideally, this will help identify appropriate animal models and age ranges for continued study of both normative development and in contexts of environmental disruption.
... B. auf Spielverhalten (z. B.Alexander & Saenz, 2012;Beltz et al., 2013). Das resultierende Spielverhalten hätte dann einen Trainingseffekt hinsichtlich der im jeweiligen Spielen relevanten Eigenschaften(Ceci, Williams & Barnett, 2009;Valla & Ceci, 2011). ...
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Die vorliegende Schrift stellt eine zusammenfassende Erörterung von sechs meiner Veröffentlichungen der letzten Jahre dar, die sich empirisch mit Sprache, Kommunikation und Medien befasst haben. Diese sechs Veröffentlichungen werden einerseits entlang einer klassischen Mediensystematik (Primär-, Sekundär-, Tertiär- und Quartärmedium) sowie entlang der einzelnen Lebensleistungen der Lebensgeschichtstheorie (somatisch, Paarungsleistung, elterlich, nicht-elterlich) geordnet. Bei den sechs Veröffentlichungen handelt es sich um empirische Arbeiten, die u. a. folgende Ergebnisse zutage förderten: Es existieren Geschlechterunterschiede in der Sprachkompetenz von Vorschulkindern, die zum Teil durch einen Marker für pränatales Testosteron erklärt werden können. Die sprachliche Gewandtheit einer Person hat einen Einfluss darauf, wie attraktiv diese wahrgenommen wird, vor allem im Kontext einer langfristigen Partnerwahl. Pseudonyme erlauben hocheffektstarke Rückschlüsse auf das Geschlecht des Pseudonymverwenders; außerdem werden von Männern verwendete Pseudonyme als deutlich kreativer bewertet als von Frauen verwendete Pseudonyme. Es existieren Geschlechtsstereotype über den Filmgeschmack von Frauen und Männern, die angesichts tatsächlicher Geschlechterunterschiede im Filmgeschmack jedoch nicht gänzlich falsch sind. Diese Geschlechterunterschiede beziehen sich auf Genres, die einen Zusammenhang zu geschlechtsdifferenten Herausforderungen die Partnerwahl und damit assoziierte Phänomene betreffend erkennen lassen. Videospiele werden überwiegend von Männern im reproduktionsrelevanten Alter geschaffen. Die sechs Studien stehen vielfältig miteinander in Beziehung; teils wird diese Beziehung zusätzlich erläuternd dargelegt, teils werden ergänzend über die sechs Studien hinausgehende (eigene) empirische Daten präsentiert, die den Zusammenhang noch stärker herstellen und so verdeutlichen. Zwei Aspekte ziehen sich durch alle bzw. fast alle der sechs Arbeiten: Geschlecht und sprachliche Fähigkeiten.
... Considering digit ratios, the study of Knickmeyer and colleagues (2011) also shows no differences in 2D:4D in younger cohorts which is in line with our results 16 . This is in fact comparable to other findings that could not find sex differences in 2D:4D in younger cohorts [55][56][57][58][59] . This questions the assumption that 2D:4D is sexually dimorphic as early as the prenatal age 19,51 and independent of age effects 17 . ...
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Hands and digits tend to be sexually dimorphic and may reflect prenatal androgen exposure. In the past years, the literature introduced several hand and digit measures, but there is a lack of studies in prepubertal cohorts. The available literature reports more heterogeneous findings in prepubertal compared to postpubertal cohorts. The comparability of the available studies is further limited by the study design and different measurement techniques. The present study compared the reliability and sex differences of available hand and digit measures, namely digit lengths of 2D, 3D, 4D, 5D, digit ratios 2D:4D, 2D:5D, 3D:4D, 3D:5D, 4D:5D, relative digit lengths rel2, rel3, rel4, rel5, directional asymmetry of right and left 2D:4D (Dr-l), hand width, length, and index of 399 male and 364 female 6-month-old German infants within one study using only indirect and computer-assisted measurements. The inter-examiner reliability was excellent while the test-retest reliability of hand scans was only moderate to high. Boys exhibited longer digits as well as wider and longer hands than girls, but smaller digit ratios, with ratios comprising the fifth digit revealing the largest effect sizes. Other hand and digit ratios revealed sex differences to some extent. The findings promote the assumption of sexual dimorphic hand and digit measures. However, by comparing the results of the available literature, there remains an uncertainty regarding the underlying hypothesis. Specifically in prepubertal cohorts, i.e. before the influence of fluctuating hormones, significant effects should be expected. It seems like other factors than the influence of prenatal androgens contribute to the sexual dimorphism in hand and digit lengths.
... Based on the same cohort, a correlation of the obtained salivary testosterone values (EIA) at the age of 3-4.9 months with play behavior and eye-contact time at the age of 19 months was analyzed. It was observed that there was no influence of salivary testosterone levels during minipuberty on gender-linked play behavior [58] or eye-contact time [59] in young children of either sex. ...
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Minipuberty describes the transient sex-specific activation of the hypothalamic-pituitary-gonadal (HPG) axis during the first 6 months of life in boys and during the first 2 years in girls. It leads to a rise of luteinizing hormone, follicle-stimulating hormone, estradiol, and testosterone. The existence of minipuberty has been known for >40 years, but we still do not fully understand why it takes place. Current thinking suggests that it is an essential imprinting period for different body functions. Firstly, minipuberty plays an important role in genital organ development; testosterone influences penile growth, the number of Sertoli cells, and spermatogenesis. Secondly, it seems to influence the infant's body composition; testosterone likely has an imprinting effect on BMI and body weight of boys and growth velocity in the first 6 months of life. Thirdly, it affects cognitive functions; testosterone has an impact on language organization in the infant brain and estradiol affects laryngeal sound production and baby babbling. There are inconsistent findings concerning the impact of minipuberty on sex-specific playing behavior. Minipuberty is an interesting field of research, and further studies in this area will teach us more about this exciting period of human development.
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There is sparse evidence suggesting the participation of neuroendocrine mechanisms, mainly involving sex and stress steroid hormones, to the pathophysiology of neurodevelopmental disorders such as Tourette syndrome (TS) and obsessive-compulsive disorder (OCD). Patients with TS exhibit a sex-specific variability in gender distribution (male/female ratio=3-4/1) and in its natural history, with a severity peak in the period around puberty. The administration of exogenous androgens may worsen tics in males with TS, whereas drugs counteracting the action of testosterone might show some antitic efficacy. This suggests a higher susceptibility of patients with TS to androgen steroids. There are insufficient data on the regulation of the hypothalamic-pituitary-gonadal (HPG) axis in TS. However, preliminary evidence suggests that a subgroup of women with TS might be more sensitive to the premenstrual trough of estrogen levels. Patients with TS exhibit differences in a number of behavioral, cognitive, and anatomical traits that appear to be sex related. There is a body of evidence supporting, albeit indirectly, the hypothesis of an increased exposure to androgenic steroids during the very early phases of neural development. Animal models in rodents suggest a complex role of gonadal hormones upon the modulation of anxiety-related and stereotyped behaviors during adult life. Patients with TS exhibit an enhanced reactivity of the hypothalamic-pituitary-adrenal axis to external stressors, despite a preserved diurnal cortisol rhythm and a normal restoration of the baseline activity of the axis following the acute stress response. Preliminary evidence suggests the possible implication of oxytocin (OT) in disorders related to the TS spectrum, especially non-tic-related OCD. The injection of OT in the amygdala of rodents was shown to be able to induce hypergrooming, suggesting the possible involvement of this neuropeptide in the pathophysiology of complex, stereotyped behaviors. In contrast, there is anecdotal clinical evidence that tics improve following periods of affectionate touch and sexual intercourse.
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The objective of the current study was to investigate the relationship between testosterone collected at 3-4 months of age and sex-linked disorder-relevant behaviors in the second year of life. Eighty-four children participated at 3-4 (when salivary testosterone levels were obtained and second to fourth digit ratios were measured) and 18-24 months of age (when behavioral ratings of aggression and verbal ability were coded from two 8-minute play sessions). Parents also completed the Brief Infant-Toddler Social Emotional Assessment, and the four subscales (Internalizing, Externalizing, Dysregulation, and Autism Spectrum Disorder) were used to indicate child specific problems. Greater postnatal testosterone levels in early infancy were predictive of more male-typical behaviors in the second year of life (i.e., more autism spectrum behaviors, less time vocalizing, and more Internalizing Problems). These results support the hypothesis that early infancy may be another critical period for the development of gender-linked behavior.
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Mikołajewska Emilia, Komendziński Tomasz, Dreszer Joanna, Bałaj Bibianna, Mikołajewski Dariusz. Role of toys in the development of healthy infants. Journal of Education, Health and Sport. 2015;5(4):219-223. ISSN 2391-8306. DOI: 10.5281/zenodo.16845 http://ojs.ukw.edu.pl/index.php/johs/article/view/2015%3B5%284%29%3A219-223 https://pbn.nauka.gov.pl/works/554832 http://dx.doi.org/10.5281/zenodo.16845 Formerly Journal of Health Sciences. ISSN 1429-9623 / 2300-665X. Archives 2011 – 2014 http://journal.rsw.edu.pl/index.php/JHS/issue/archive Deklaracja. Specyfika i zawartość merytoryczna czasopisma nie ulega zmianie. Zgodnie z informacją MNiSW z dnia 2 czerwca 2014 r., że w roku 2014 nie będzie przeprowadzana ocena czasopism naukowych; czasopismo o zmienionym tytule otrzymuje tyle samo punktów co na wykazie czasopism naukowych z dnia 31 grudnia 2014 r. The journal has had 5 points in Ministry of Science and Higher Education of Poland parametric evaluation. Part B item 1089. (31.12.2014). © The Author (s) 2015; This article is published with open access at Licensee Open Journal Systems of Kazimierz Wielki University in Bydgoszcz, Poland and Radom University in Radom, Poland Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. The authors declare that there is no conflict of interests regarding the publication of this paper. Received: 15.02.2015. Revised 27.03.2015. Accepted: 10.04.2015. Role of toys in the development of healthy infants Emilia Mikołajewska1,2,3, Tomasz Komendziński3,4, Joanna Dreszer3,4, Bibianna Bałaj3,4, Dariusz Mikołajewski3,5,6 1 Department of Physiotherapy, Ludwik Rydygier Collegium Medium in Bydgoszcz, Nicolaus Copernicus University in Toruń 2 Rehabilitation Clinic, The 10th Clinical Military Hospital with Policlinic, Bydgoszcz, Poland 3 Neurocognitive Laboratory, Interdisciplinary Center for Modern Technologies, Nicolaus Copernicus University in Toruń 4 Department of Cognitive Science, Nicolaus Copernicus University, Toruń, Poland 5 Institute of Mechanics and Applied Computer Sciences, Kazimierz Wielki Universit, Bydgoszcz, Poland 6 Department of Informatics, Nicolaus Copernicus University, Toruń, Poland Corresponding author: Emilia Mikołajewska Rehabilitation Clinic Military Clinical Hospital No. 10 and Polyclinic Bydgoszcz, Poland e-mail: e.mikolajewska@wp.pl, emiliam@cm.umk.pl www: http://emikolajewska.netstrefa.eu Keywords: rehabilitation; development; gesture; toy use; parent–child interaction; Abstract Developmental outcomes in infants can be significantly improved thanks to promising use of approapriate toys. Objective assessment of their positive influence to functional achievements in healthy infants may completely change attitude to new generation of toys, developing motor, cognitive, and social skills. Despite advances in toys assessment their true influence remains incomplete. This study aims at assessment how current knowledge and experience influences principles of the toys selection and use in healthy infants.
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Background/Objective Although the physiology of minipuberty are well‐established, it is not fully explained why it occurs. It has been suggested that minipuberty contributes to the development of reproductive organs, somatic growth, cognitive/behavioral, and sex‐specific brain development. Given the well‐known trade‐off between the reproductive/endocrine and immune systems in adults, the immunological approach to minipuberty, which is characterized by transient activation of the hypothalamo‐pituitary gonadal (HPG) axis seems to be ignored. This study focused on the relationship of the lymphocyte subsets with gonadotrophin and sex hormones during the minipuberty. Materials and Methods A total of 121 newborns (58 male) were included in this cross‐sectional study. The hormone and lymphocyte subsets studied were as follow:follicle‐stimulating hormone (FSH), luteinizing hormone (LH) estradiol (E), testosterone (T), CD19, CD16/56, CD3, CD3/CD4, CD3/CD8, and HLA‐DR as lymphocyte activation marker. Results The mean FSH levels were higher in females (15.15±10.12mIU/mL vs, 2.61±1.74mIU/mL) and LH in males (5.80±2.51mIU/mL vs. 1.91±12.89mIU/mL) (p<0.001 for each). The mean percentages of the CD3/CD4 levels were higher in females (54.61±6.70% vs. 51.17±6.77%) and CD3/CD8 in males (21.49±4.82% vs. 17.31±3.66%) (p <0.001 for each). In the females, the mean FSH levels negatively correlated with CD3/CD4 (rFSH‐CD3/CD4=‐0.423, p=0.001) and positively correlated with CD3/CD8 (rFSH‐CD3/CD8=0.311, p=0.013). In the males, LH positively correlated with CD3/CD4 (rLH‐CD3/CD4=0.406, p<0.001) and negatively correlated with CD3/CD8 (rLH‐CD3/CD8=‐0.486, p<0.001). Conclusion This study showed that the mean CD3/CD4 levels were higher in female and CD3/CD8 in male newborns, indicating that there was a sexual dimorphism in favor of immunostimulant in females and immunosuppressor components of immune response in males during the minipuberty. These interactions point to sex‐specific trade‐off between reproductive/endocrine and immune systems, which it reflects the an investment favoring in the reproductive system against the immune response during minipuberty, which is critical period for adult fertility, especially in males
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Evidence indicating that sex-linked toy preferences exist in two nonhuman primate species support the hypothesis that developmental sex differences such as those observed in children's object preferences are shaped in part by inborn factors. If so, then preferences for sex-linked toys may emerge in children before any self-awareness of gender identity and gender-congruent behavior. In order to test this hypothesis, interest in a doll and a toy truck was measured in 30 infants ranging in age from 3 to 8 months using eye-tracking technology that provides precise indicators of visual attention. Consistent with primary hypothesis, sex differences in visual interest in sex-linked toys were found, such that girls showed a visual preference (d > 1.0) for the doll over the toy truck and boys compared to girls showed a greater number of visual fixations on the truck (d = .78). Our findings suggest that the conceptual categories of "masculine" and "feminine" toys are preceded by sex differences in the preferences for perceptual features associated with such objects. The existence of these innate preferences for object features coupled with well-documented social influences may explain why toy preferences are one of the earliest known manifestations of sex-linked social behavior.
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The differentiation of the urinogenital system and the appendicular skeleton in vertebrates is under the control of Hox genes. The common control of digit and gonad differentiation raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations. This work was concerned with the ratio between the length of the 2nd and 4th digit (2D:4D) in humans. We showed that (i) 2D:4D in right and left hands has a sexually dimorphic pattern; in males mean 2D:4D = 0.98, i.e. the 4th digit tended to be longer than the 2nd and in females mean 2D:4D = 1.00, i.e. the 2nd and 4th digits tended to be of equal length. The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight.
Article
Sex differences in children's toy preferences are thought by many to arise from gender socialization. However, evidence from patients with endocrine disorders suggests that biological factors during early development (e.g., levels of androgens) are influential. In this study, we found that vervet monkeys (Cercopithecus aethiops sabaeus) show sex differences in toy preferences similar to those documented previously in children. The percent of contact time with toys typically preferred by boys (a car and a ball) was greater in male vervets (n=33) than in female vervets (n=30) (P
Article
The sexually differentiated second-to-fourth digit ratio (2D:4D) is currently frequently utilized in individual differences research as a putative indicator of the masculinizing brain organization effects of prenatal testosterone. This preamble introduces the journal special issue on this theme, entitled “Digit ratio (2D:4D) and individual differences research”. Notes regarding the background, history, and recent progress of 2D:4D research are provided, and the background of the special issue and the contents of its 11 research articles are briefly summarized.
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2 sets of scales were developed designed to measure the strength of sex typing in children's play patterns in a naturalistic setting. Over a 12-week observational period, the scales based upon those activities showing a sex difference in play preferences appeared to be more stable than those scales based upon adult ratings of masculine and feminine activities. Masculine and feminine activity preferences, as measured by the more stable scales, were correlated with observational measures of other classroom behavior and performance on 3 cognitive tests. These results suggested that (a) many children have already learned to avoid opposite-sex activities by the time they enter nursery school; (b) sex-role learning during the preschool period appears to involve increasing attention to same-sex activities; and (c) the development of visual-spatial ability in boys is related to involvement in masculine activities. The advantages of a behaviorally based definition of masculine and feminine activity preference are discussed.
Article
The second to fourth digit ratio (2D:4D) is sexually dimorphic, with lower mean values in males compared to females. It has been suggested that the sex difference in 2D:4D is determined prenatally, 2D:4D is negatively related to prenatal testosterone and positively to prenatal oestrogen, and that 2D:4D is a marker for levels of sex steroids during brain organisation. There is growing evidence that many sex-dependent behaviours are correlated with 2D:4D. However, there is no direct evidence for an effect of prenatal sex steroids on the digit ratio. The response to prenatal testosterone is dependent on the amount produced and the foetal sensitivity to the hormone. Variation in the X-linked androgen receptor gene (AR) determines sensitivity to testosterone. Alleles of AR with low numbers of CAG triplets respond to testosterone with high transactivational activity, while high numbers of CAG's are associated with increased insensitivity to testosterone. We show in a sample of 50 men (49 Caucasian subjects, 1 Caucasian/Chinese subject) that 2D:4D is a phenotypic correlate of AR structure. Right-hand 2D:4D was positively correlated with CAG number and individuals with low 2D:4D in their right hand compared to left hand had AR alleles with low CAG numbers. We discuss the implications of our findings for our understanding of the aetiology of 2D:4D, its relationships with sex-dependent behaviours, and the evolutionary implications of variation in 2D:4D and AR.
Article
Infants’ visual preferences for gender-stereotyped toys and their knowledge of stereotyped toys were examined in two experiments using an adaptation of the preferential looking paradigm. Girls and boys aged 12, 18, and 24 months were tested for their preference for photos of vehicles or dolls, and for whether they associated (“matched”) these two stereotyped sets of toys with the faces and voices of male and female children. Results of Experiment 1 (N = 77) demonstrated significant preferences for gender stereotyped toys appearing by 18 months of age. In Experiment 2 (N = 58), girls were able to associate the gender-stereotyped toys with girls’ and boys’ faces by 18 months of age, but boys were not. Implications for theories of early gender development are discussed.
Article
A gender difference in motor activity level (AL) is well established for children, but questions about the existence and nature of an infant sex difference remain. To assess these questions, we applied meta-analytic procedures to summarize 46 infancy studies comprising 78 male–female motor activity comparisons. Our results showed that, as with children, male infants were more active than females. Objective measures of infant AL estimated the size of this difference to be 0.2 standard deviations, though subjective parent-report measures estimated the difference to be smaller. We argue that this early sex difference in activity level is biologically based. However, socialization processes, such as gender-differentiated expectations and experiences, in conjunction with further sex-differentiated biological developments, amplify this early difference to produce the larger gender differences in activity found during childhood. Copyright © 1999 John Wiley & Sons, Ltd.
Article
Girls with cong~nital adr~nal hyp~rplasia (CAR) who w~r~ ~xpos~d to high '~v~ls 01 andro,~n in th~ pr~natal and ~arly postnatal p~riods show~d in- cr~as~dp/Qy with boys' toys and r~duc~d play with girls' toys compar~d with th~ir un~xpos~d I~ma/~ r~/atives at a,~s 3 to 8. Boys with CAR did not differ from th~ir ma/~ r~/atives in play with boys' or girls' toys. Th~se r~sults sugg~st that early hormon~ exposur~ in/~males has a masculinizing ~ff~ct on s~x-typ~d toy pr~/erences. the patient or control status of subjects. We hypothesized that CAH girls would show 8feater preference for boys' toys than their unaffected female relatives, and reduced preference for girls' toys. We did not predict effects for CAH boys because androgen treatment has incon. sistent effects in male experimental ani- mals (Baum &. Schretlen, 197.5; Dia. mond. Llacuna, & Wong, 1973).
Article
Toddler children and their parents were observed in their homes using an observation checklist of 46 child behaviors and 19 reactions by parents. The parent behaviors were categorized as positive, negative, or neutral, and parental reactions to specific child behaviors were examined to determine if the sex of the child or the actual behavior influenced the type of parental reaction. It was found that parents reacted significantly more favorably to the child when the child was engaged in a same-sex-preferred behavior and were more likely to give negative responses to cross-sex-preferred behaviors. Parents gave girls more negative responses when engaged in active, large motor activities. They gave girls more positive responses when they engaged in adult-oriented, dependent behavior. No difference in parental reaction toward boys and girls was present for aggressive behavior. Parents' self-report data and the observation of parents reactions did not correlate highly.
Article
Conducted naturalistic observations of the play of 52 14–35 mo old toddlers (28 girls and 24 boys) with a set of socially stereotyped masculine, feminine, and neutral toys in a daycare setting over 14 mo. In addition, 2 potential influences on toy choice were investigated: parental expectations of play and Ss' gender knowledge. Results show that Ss played more often with toys stereotyped for their own gender than with the other toys. Girls' play with feminine toys increased with age, but boys' play with masculine toys did not vary with age, partly because even the youngest boys chose masculine toys frequently. Parents provided same-sex-typed toys for their children and made sex-typed predictions of their children's toy choices, but these measures were not clearly related to children's play. Cognitive change in understanding of gender was related to toddler boys' early sex-typed behavior. (17 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Observed 47 preschool girls (2.5–4 yrs old) in social interaction with boys and girls. For young Ss, feminine toy preference was positively related to interaction with girls, whereas masculine toy choice was positively associated with interaction with boys. For older girls, feminine toy choice was positively related to interaction with girls. Large, older girls tended to play with masculine toys. (5 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
A gender-labeling task was used to test the ability of 21 girls and 22 boys ranging in age from 21 to 40 mo to discriminate between pictures of boys and girls and male and female adults. Ss who passed the gender task (mean age 30 mo) were compared with Ss who failed it (mean age 26 mo) on 3 behaviors most often categorized as sex typed (toy choice, aggression, and peer playmate selection). It was predicted that Ss who passed the task would choose more sex-typed toys and same-sex peers and that there would be a drop in aggression for girls who passed but no change for boys. Results confirm the predictions for aggression and peer choice but not for toy choice. The relation between the child's understanding of gender categories and environmental influences is discussed. (18 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Based upon studies of children's sex-typed behaviours, it is theorized that a forceful, forward motor behaviour, or propulsion, is an integral component of several masculine sex-typed behaviours. To test the relation between propulsion and masculinity, a game of tag was designed to elicit propulsion from 3- to 5-year-old children. In addition, in Study 1, teachers rated children's degree of masculinity and, in Study 2, the masculinity of children's toy preferences was assessed. Results showed a significant relation between propulsion and measures of masculinity. Findings are discussed in terms of the importance of considering motor behaviour in studies of sex typing.
Article
Sex differences in social behaviour emerge as early as 2 years of age and gender schema theorists have suggested that preverbal infants possess ‘tacit’ knowledge of gender which informs their behaviour. This study examined sex-congruent preferences using a visual preference paradigm in four domains (babies, children, toys, activities) in a longitudinal study of infants aged 3, 9 and 18 months. At 3 months, infants showed a marginally significant preference for same-sex babies driven principally by males. Sex-congruent toy preference was found among males at ages 9 and 18 months. Both sexes preferred masculine activity styles but this effect was significantly stronger among males than females. Gender schema theory requires gendered self-concept as a precursor to sex-congruent preference. Infants did not recognize themselves from photographs at any of the ages tested. By 18 months approximately two thirds of infants showed self-recognition on the rouge test. However, at none of the ages and in none of the domains tested was self-recognition related to sex-congruent preference. Cross-domain consistency of preference was not found. There was evidence of some stability of preference within domains between the ages of 9 and 18 months and this stability was very marked for activity preference.
Article
This cross-sectional study investigated toy-choice in 38 one-year-old, 33 three-year-old, and 35 five-year-old children, who could choose between 10 different toys (four feminine, four masculine, and two neutral) in a structured play-session. The children played alone for 7 minutes and together with their accompanying parent for another 7 minutes (play-status). The results showed that girls and boys chose different toys from as early as the age of one year (Mdn=12 months). These sex differences were found at all three ages. In contradiction to earlier studies, our results showed that feminine toys became less interesting for both girls and boys with increasing age. The present study showed no consistent effects of play-status. This study contributes to the knowledge of how early behavioral sex differences can be observed, how these differences develop, and it also raises questions concerning what sex differences stem from.
Article
The relative contribution of gender labels and play styles (masculine or feminine) in playmate selection was evaluated in 60 children between the ages of 4 and 8 years using a novel interview measure. In the interview, when targets' gender labels and targets' play styles were presented as independent dimensions, children showed predicted sex differences in preferences for gender labels and for play styles (including toys, rough-and-tumble play, and activity level). However, when targets' gender labels and targets' play styles were presented as competing dimensions, boys of all ages chose female targets with masculine play styles over male targets with feminine play styles. In contrast, younger girls (4–5-year-olds) chose female targets with masculine play styles, whereas older girls (6–8-year-olds) chose male targets with feminine play styles. This suggests possible sex differences in the contribution of gender labels and of play styles in the development of children's preferences for same-sexed playmates.
Article
Kindergarten children were videotaped playing with female- and male-traditional toys as well as nonsex-typed toys. Coders calculated time spent by each child in behavioral categories (positive and negative comments, aggression, nurturance, movement, noise, and gadgetry) and rated children on scales (talkativeness, activity, familiarity, enjoyment, proximity, appropriateness, and gentleness). Sex differences were revealed on most dimensions. Boys were rated as familiar with, enjoying, and playing appropriately with two toys (male-traditional and nonsex-typed) and girls on the female-traditional toy. Girls paid more attention to details of the toys, while there were few differences on aggression and movement. Data suggest that children develop varying patterns of play with the same toy—based on their earlier experiences with play materials. Agents promoting these differences (parents, teachers, and peers) are discussed, as are implications of the findings for children's development of skills and cognitive abilities.
Article
This study examined the gender-typed portrayal of material culture in Caldecott Award children's books published between 1937 and 1989. Analyses of illustrations found that a larger proportion of female characters was shown using household artifacts, and a larger proportion of male characters was depicted using nondomestic production artifacts. Contrast analyses revealed no change over time in the proportions of female characters portrayed using household and production artifacts. Children's exposure to this representation may result in gender-linked modeling effects on preferences and skills related to technology and other material culture.
Article
This study assessed the diagnostic potential of the actigraph, the Continuous Performance Test, and the Matching Familiar Figures Test in diagnosing attention-deficit hyperactivity disorder (ADHD). Twenty boys previously diagnosed with ADHD and 52 controls were examined. By these measures the boys with ADHD were differentiated from the controls with sensitivity and specificity above 75%. We were able to classify ADHD into eight subtypes by combining the scores of the actigraph and the CPT: hyperactive-impulsive, hyperactive-inattentive, impulsive-inattentive, hyperactive, impulsive, inattentive, mixed, and unspecified type. These classifications may be useful in diagnosing ADHD.
Article
Sexual dimorphism in sociability has been documented in humans. The present study aimed to ascertain whether the sexual dimorphism is a result of biological or socio-cultural differences between the two sexes. 102 human neonates, who by definition have not yet been influenced by social and cultural factors, were tested to see if there was a difference in looking time at a face (social object) and a mobile (physical-mechanical object). Results showed that the male infants showed a stronger interest in the physical-mechanical mobile while the female infants showed a stronger interest in the face. The results of this research clearly demonstrate that sex differences are in part biological in origin.
Article
Twelve-month-old infants (n=60) were presented with a video of cars moving, or a face moving, in a looking preference experimental design. This tested the prediction from our earlier work that attention in males is drawn more to mechanical motion, whilst attention in females is drawn more to biological motion. Results supported this prediction. These findings are discussed in relation to social and biological determinism.
Article
The testes are active during gestation, as well as during early infancy. Testosterone elevation during fetal development has been shown to play a role in human neurobehavioral sexual differentiation. The role of early postnatal gonadal activation in human psychosexual development is largely unknown, however. We measured testosterone in 48 full term infants (22 boys, 26 girls) by monthly urinary sampling from day 7 postnatal to age 6 months, and related the area under the curve (AUC) for testosterone during the first 6 months postnatal to subsequent sex-typed behavior, at the age of 14 months, using the Pre-School Activities Inventory (PSAI), and playroom observation of toy choices. In boys, testosterone AUC correlated significantly with PSAI scores (Spearman's rho = 0.54, p = 0.04). In addition, play with a train and with a baby doll showed the anticipated sex differences, and play with the train correlated significantly and positively with testosterone AUC in girls (Spearman's rho = 0.43, p = 0.05), while play with the doll correlated significantly and negatively with testosterone AUC in boys (Spearman's rho = -0.48, p < 0.03). These results may support a role for testosterone during early infancy in human neurobehavioral sexual differentiation.
Article
The relative lengths of the 2nd and 4th digits (2D:4D) may provide an easily measurable and stable anthropometric index of prenatal androgen exposure, but no study has examined the development of 2D:4D in infancy and the potential impact of neonatal testosterone levels. We collected 2D:4D ratios from 364 children between 0 and 2 years of age. Saliva samples were collected from 236 of these children 3 months after birth and analyzed for testosterone. In addition, 259 children provided DNA samples which were genotyped for the CAG repeat polymorphism in the androgen receptor. There was substantial variability across age in 2D:4D. Sex differences were small compared to adults and did not consistently reach statistical significance. This suggests that 2D:4D may not function well as a proxy measure of prenatal testosterone exposure in infancy. In addition, the interaction of salivary T and CAG repeats predicted right hand digit ratio at 12 months and left hand digit ratio at 12 months and 24 months in males. The interaction of salivary testosterone and CAG repeat length also predicted change in left hand 2D:4D from 2 weeks to 12 months in males. This suggests that 2D:4D in adults may reflect, in part, neonatal testosterone exposure. No significant relationships were observed within females. No significant relationships were observed when salivary testosterone and CAG repeats were examined independent of each other. Results have important implications for the design and interpretation of studies which use 2D:4D as a proxy measure of prenatal testosterone exposure.
Article
Both sexual orientation and sex-typical childhood behaviors, such as toy, playmate and activity preferences, show substantial sex differences, as well as substantial variability within each sex. In other species, behaviors that show sex differences are typically influenced by exposure to gonadal steroids, particularly testosterone and its metabolites, during early development (prenatally or neonatally). This article reviews the evidence regarding prenatal influences of gonadal steroids on human sexual orientation, as well as sex-typed childhood behaviors that predict subsequent sexual orientation. The evidence supports a role for prenatal testosterone exposure in the development of sex-typed interests in childhood, as well as in sexual orientation in later life, at least for some individuals. It appears, however, that other factors, in addition to hormones, play an important role in determining sexual orientation. These factors have not been well-characterized, but possibilities include direct genetic effects, and effects of maternal factors during pregnancy. Although a role for hormones during early development has been established, it also appears that there may be multiple pathways to a given sexual orientation outcome and some of these pathways may not involve hormones.
Article
Recent research showing associations between behavior and postnatal testosterone levels in male infants has suggested that the transient activation of the hypothalamic-pituitary-gonadal axis in early infancy may influence the expression of gender phenotypes in later development (i.e., the postnatal hormone hypothesis). As a further test of the relationship between postnatal hormones and behavior in infancy, we measured digit ratios and salivary testosterone in 76 male and female infants (3-4 months of age) and parents completed the Infant Behavior Questionnaire-Revised, a well-established measure of temperament in the first year of life. Consistent with our earlier findings, there were no significant sex differences in salivary testosterone levels and testosterone levels were unrelated to measures of behavior in female infants. However, in male infants, higher androgen levels predicted greater Negative Affectivity. Further examination of the four scales contributing to the measure of Negative Affectivity showed testosterone levels were a significant predictor of scores on the Distress to Limitations scale, but not of scores on Fear, Sadness, or Reactivity scales. This sex-specific association between salivary testosterone and behavior in infants is consistent with animal research showing higher prenatal androgens associated with typical male development lower the threshold of sensitivity to endogenous testosterone in postnatal life. In sum, these data provide additional support for the postnatal hormone hypothesis and suggest postnatal testosterone levels may influence the development of emotional regulation in male infants.
Article
To provide an overview of the methods that have been developed for measurement of physical activity in children of preschool age. Emphasis will be given to direct observation and accelerometry, but pedometry, HR monitoring, and proxy reports will be reviewed as well. Research articles detailing the measurement properties of direct observational systems, accelerometry, pedometry, HR monitoring, and proxy reporting specifically in children of preschool age were selected and reviewed. Systems for direct observation of physical activity and accelerometry are valid and reliable measures of physical activity in young children. Direct observation, which can provide information on type and context of physical activity, is an excellent complement to accelerometry, which provides detailed information on the intensity and duration of physical activity but no contextual information. Direct observation systems and accelerometry have become well-established measurements of physical activity in young children as well as older groups. Pedometry and HR monitoring have been shown to be applicable, but these methods have been studied less extensively than direct observation and accelerometry. Proxy reports of physical activity are attractive because of low burden, but they have limited validity.
Article
The purpose of this study was to evaluate the influence of the location (ankle, hip, wrist) where an activity monitor (AM) is worn and of the minimum bout duration (BD) on physical activity (PA) variables during free-living monitoring. Study 1 participants wore AMs at three locations for 1 day while wearing the Intelligent Device for Energy Expenditure and Activity (IDEEA) system. Study 2 participants wore AMs at the same locations for 3 days. Variables included time (T(MV), min/day) and AEE (AEE(MV) kcal/day) for each monitor location and BD above a moderate-vigorous (MV) intensity. T(MV) and AEE(MV) in Study 1 were similar across AMs to IDEEA values at BD = 10 min, as was T(MV) in Study 2. This suggests that ankle-, wrist- and hip-worn AMs can provide similar PA outcome values during free-living monitoring at 10-min BDs.
Article
The physiological significance of hormonal changes in early postnatal life is emerging, but the behavioral significance in humans is unknown. As a first test of the relationship between hormones and behavior in early infancy we measured digit ratios and salivary hormone levels in forty-one male and female infants (3-4 months of age) who watched a video depicting stimuli differentially preferred by older males and females (toys, groups). An eye-tracker measured visual fixations and looking times. In female infants, hormones were unrelated to visual preferences. In male infants, higher androgen levels predicted stronger preferences for male-typical stimuli. These data provide the first evidence for a role for hormones in emerging sex-linked behavior in early development.
Article
(1) Studies on the long-term effects of progesterone administration during gestation have suggested that it has a mild influence on postnatal female behavior causing even greater femininity than expected in normal controls. (2) However, it has been difficult to distinguish the effects of the prenatal hormone from those of the maternal disease state (toxemia). (3) In a new study, girls (n= 15) with prenatal exogenous hormonal exposure due to maternal intake of medroxyprogesterone acetate (MPA) were compared with a closely matched control group. (4) The results suggested that MPA was not associated with genital abnormalities in genetic females. (5) Behavior effects of prenatal MPA appeared to be subtle and included a lower incidence of being labeled a tomboy during childhood and a more constant preference for feminine clothing styles. (6) We conclude that prenatal MPA may have an enhancing effect on female sexually dimorphic behavior.
Article
Observations were made in the homes of 32 families, each with a child aged around 12 or 24 months. 16 of the children were boys and 16 girls. Boys showed more active play, play with transportation toys, and play generally forbidden by parents. Girls played more with soft toys and dolls. On questionnaire responses many parents rated these and other behaviors as sex appropriate. However, actual sex differences in immediate parental response to children were few or undetected. Sex differences in children's behavior did not appreciably increase from 12 to 24 months. Also, there was no correlation with how stereotyped parents' questionnaire responses were and the degree to which their children exhibited sex-typed behavior.
Article
Sex differences in social play are quantitative and not qualitative, referring to frequency and not the form of the behaviors. Whereas increased perinatal exposure to exogenous testosterone masculinizes social play, experimental manipulations of androgen levels after this period (i.e. following critical periods for neuronal differentiation) apparently have no effect on the expression of social play. This effect appears to involve, at least in part, androgen receptor occupancy in the amygdala. In the rat, there is a prominent sex difference in nuclear-bound androgen receptors in the amygdala during the sensitive period for the masculinization of play-fighting. Moreover, testosterone implants directly into the amygdala during this period masculinize social play in females. Progesterone exposure reduces play-fighting in male rats, as does corticosterone. This latter effect may be mediated by corticosteroid receptors in the limibic brain. Perinatal androgen exposure may also be important in humans, since girls born with congenital adrenal hyperplasia diagnosed and treated at birth still show male-like patterns of play. Theories concerning the function of sex differences in social play emphasize either the social or motor learning functions. Juvenile male primate social rank correlates with number of peer social interactions, which predominantly take the form of play-fighting. Females on the other hand appear to spend less time play-fighting and spend more time waiting and competing for interactions with infants, i.e. play-mothering, whereby they acquire the motor skills necessary for handling infants. Such differences may reflect socio-biological and developmental cascades that are, in some way, initiated by perinatal hormonal events.
Article
Motor activity level, or customary energy expenditure through movement, is a cornerstone dimension of temperament. In this article we address the unresolved question of sex differences in activity level (AL) by quantitatively integrating results from 90 citations encompassing 127 independent sex difference contrasts. Males are generally more active than females, d = .49, although the magnitude of the difference is associated with other features of the research investigation, such as participant age and situational characteristics. This AL result is judged a large effect within the context of established behavioral sex differences, and implications are discussed.
Article
Testicular steroidogenic activity in 22 boys was monitored longitudinally over the first 6 months of life using salivary T measurements. Samples were collected biweekly. The highest T levels, 130 +/- 12 pmol/liter (mean +/- SE, n = 22), were observed on days 2-10. The values then gradually declined to a mean of about 30 pmol/liter after month 4. No secondary peak in salivary T appeared, in contrast to the 1-3 month peak in serum T previously reported. The overall levels of T, reflected by the areas under the T concentration curves over the whole period, varied by a factor of three among the subjects studied. It is concluded that postnatal testicular activity may have its most marked physiologic effects immediately after birth rather than at the time of the 1-3-month peak of serum T. Furthermore, the overall exposure to androgen is individually greatly variable.
Article
In the first study, the motor activity level and vigor of play of 52 toddlers was assessed as they played with a set of sex-role stereotyped and neutral toys. Boys and girls showed the same level of activity, and both were significantly more active when playing with stereotypically masculine toys. In the second study, 27 toddlers were observed playing with toys defined as potentially eliciting high, medium, or low activity within the masculine, feminine, and neutral categories. Again, boys and girls did not differ in overall activity level. All children preferred toys that allowed moderate to high activity, but given this preference, they selected toys stereotyped for their own gender above those stereotyped for the other gender.
Article
Total and unbound testosterone and Delta(4)-androstenedione have been determined in 104 cord blood samples. The same sexual steroids and pituitary gonadotropins have been measured in 46 normal male infants aged 27-348 days and 34 normal female infants aged 19-332 days. In cord blood of female neonates mean total and unbound testosterone was 29.6+/-7.5 and 0.89+/-0.4 ng/100 ml, respectively (mean+/-1 SD); Delta(4)-androstenedione was 93+/-38 ng/100 ml. In male neonates mean plasma total and unbound testosterone was 38.9+/-10.8 and 1.12+/-0.4 ng/100 ml; Delta(4)-androstenedione was 85+/-27 ng/100 ml. In female infants testosterone concentrations remained constant during the 1st yr of life with a mean concentration of 7+/-3 ng/100 ml. Mean unbound testosterone and Delta(4)-androstenedione concentrations were 0.05+/-0.03 and 16.7+/-8.3 ng/100 ml, respectively. Mean plasma levels of follicle-stimulating hormone and luteinizing hormone were 8.7+/-3.3 and 12.9+/-7.7 mU/ml. In male infants mean plasma total testosterone concentration increased to 208+/-68 ng/100 ml from birth to 1-3 mo of age, decreasing thereafter to 95+/-53 ng/100 ml at 3-5 mo, 23.2+/-18 ng/100 ml at 5-7 mo, and reached prepubertal levels (6.6+/-4.6 ng/100 ml) at 7-12 mo. Mean unbound testosterone concentration plateaued from birth to 1-3 mo of age (1.3+/-0.2 ng/100 ml) decreasing to prepubertal values very rapidly. Mean Delta(4)-androstenedione concentration, although progressively decreasing during the 1st yr of life to 11.7+/-4.5 ng/100 ml, was higher than in the female at 1-3 mo of life (34+/-11 ng/100 ml). Mean plasma level of follicle-stimulating hormone was 6.7+/-2.9 mU/ml, and that of luteinizing hormone was 19.7+/-13.5 mU/ml, significantly higher than in the female. There was no correlation between gonadotropin and age or testosterone. The present data demonstrate that the testes are active during the first natal period. It is tempting to correlate this phenomenon to a progressive maturation of the hypothalamo-pituitary-gonadal axis. It is possible that the surge in testosterone occurring the first 3 mo could play a role in the future life pattern of the male human being.
Article
Evidence that gonadal hormones during prenatal and neonatal development influence behavior is reviewed. Several theoretical models of hormonal influences, derived from research in other species, are described. These models are evaluated on the basis of data from humans with either normal or abnormal hormonal exposure. It is concluded that the evidence is insufficient to determine which model best explains the data. Sexual differentiation may involve several dimensions, and different models may apply to different behaviors. Gonadal hormones appear to influence development of some human behaviors that show sex differences. The evidence is strongest for childhood play behavior and is relatively strong for sexual orientation and tendencies toward aggression. Also, high levels of hormones do not enhance intelligence, although a minimum level may be needed for optimal development of some cognitive processes. Directions for future research are proposed.
Article
The relative contribution of gender labels and play styles (masculine or feminine) in playmate selection was evaluated in 60 children between the ages of 4 and 8 years using a novel interview measure. In the interview, when targets' gender labels and targets' play styles were presented as independent dimensions, children showed predicted sex differences in preferences for gender labels and for play styles (including toys, rough-and-tumble play, and activity level). However, when targets' gender labels and targets' play styles were presented as competing dimensions, boys of all ages chose female targets with masculine play styles over male targets with feminine play styles. In contrast, younger girls (4-5-year-olds) chose female targets with masculine play styles, whereas older girls (6-8-year-olds) chose male targets with feminine play styles. This suggests possible sex differences in the contribution of gender labels and of play styles in the development of children's preferences for same-sexed playmates.
Article
The standard view of sexual differentiation of the brain, derived primarily from work with mammals, is that the same steroidal signal which permanently masculinizes the body early in life, androgen, also permanently masculinizes the nervous system. This oversimplified view overlooks the rich diversity of mechanisms produced by natural selection. We review the mechanisms underlying sexual differentiation of what may be the simplest mammalian model, the spinal nucleus of the bulbocavernosus (SNB), a system that is intimately associated with sexual differentiation of the periphery. Indeed, in many instances, early androgen can permanently masculinize the SNB system but, surprisingly, these early influences may depend to some extent on social mediating factors. Furthermore, in adulthood, androgen continues to affect the SNB system in diverse ways, acting on several different loci, indicating a life-long plasticity in even this simple system. Finally, there is evidence that adult androgens interact with social experience in order to affect the SNB system. Thus the SNB system displays a far richer array of interactions than the standard view of sexual differentiation would predict. Examination of other systems and other species, as depicted in the following reports, reveals a far more complicated, and far more interesting perspective on how the brains and behaviors of males and females diverge.
Article
Healthy boys have a considerable production of reproductive hormones during the first postnatal months, the biological significance of which is poorly understood. We report on cases of male infants with hypogonadism (hypogonadotropic hypogonadism, n = 1; panhypopituitarism, n = 2) who showed lack of penile growth and involution of the scrotum. In two boys, diagnoses were obtained in early infancy and hormonal measurements at 3-4 months of age showed serum testosterone levels below detection limits in both low inhibin B (37 and 199 pg/mL, respectively; normal range, 193-563 pg/mL) and low to undetectable gonadotropins [LH, undetectable and 0.07 IU/L (normal range, 0.65-2.69 IU/L), respectively; FSH, 0.18 IU/L in both (range, 0.86-2.52 IU/L)]. In a third boy, gonadotropin deficiency was diagnosed at 3 yr of age by undetectable serum levels of FSH and LH both before and after stimulation with GnRH. All cases required hormonal treatment with testosterone, administered as suppositories in daily doses between 1 and 5 mg, which reintroduced male genital development. Our observations suggest that normal phallic and scrotal development in humans is dependent on intact testosterone secretion during early infancy. Additionally, the diagnosis of gonadotropin deficiency may be established in a short-time window postnatally by measurement of spontaneous serum concentrations of reproductive hormones.