Le differenze che spesso riscontriamo tra uomini e donne sono quasi sempre un’espansione di quelle già riscontrate nel periodo infantile, per questo giova vedere queste ultime più da vicino.
In SEX DIFFERENCES IN INFANCY AND AT PLAY, David Geary ci fa da provvidenziale guida.
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L’età dello sviluppo è fondamentale nell’uomo, lo sappiamo bene. Le durate, nella nostra specie, sono dilatate proprio perché la “macchina” da mettere a punto è particolarmente sofisticata…
… The 15- to 20-year period between weaning and reproduction…
Negli scimpanzé non si va oltre i 5-7 anni.
Si tratta di un periodo molto costoso in termini di dispendio fisico e di vulnerabilità…
… the development of secondary sexual characteristics can be costly… The costs include potential suppression of immune functions, increased risk of predation (e.g., for brightly colored males), and increased aggression from conspecifics, among others….
La maturazione maschile è ritardata in anche perché deve essere più prepotente…
… delayed maturation allows males to grow larger and gain the social and behavioral competencies needed to compete for and attract mates…
Le bambine maturano prima…
… girls grow up faster than boys: that is, they reach 50% of their adult height at an earlier age …, enter puberty earlier and cease earlier to grow …. At birth the difference corresponds to 4 to 6 weeks of maturation and at the beginning of puberty to 2 years. (Tanner, 1990, p. 56)…
La probabile logica: l’età dello sviluppo è costosa visto che rende i soggetti più vulnerabili. Poiché le bambine sono la risorsa riproduttiva più preziosa della specie, va messa al sicuro quanto prima. Con i bambini invece è razionale rischiare di più: 1) non sono una risorsa così preziosa (basterebbe un uomo per inseminare tutte le donne) 2) ritardare lo sviluppo seleziona i migliori e potenzia lo sviluppo stesso.
Commento: non è solo la società umana che tende a sacrificare l’uomo, è la natura stessa a farlo.
Benefici dello sviluppo ritardato…
… The slower maturation of boys (see Garai & Scheinfeld, 1968; Hutt, 1972) appears to heighten their risk of early mortality but contributes to their adult height; later puberty results in longer legs in men than in women, relative to overall height…
Lo sviluppo maschile è particolarmente laborioso e costoso in termini energetici…
… Boys also develop larger hearts as well as larger skeletal muscles, larger lungs, higher systolic blood pressure, lower resting heart-rate, a greater capacity for carrying oxygen in the blood, and a greater power of neutralizing the chemical products of muscular exercise …. In short, the male becomes more adapted at puberty for the tasks of hunting, fighting and manipulating all sorts of heavy objects. (Tanner, 1990, p. 74)…
I cambiamenti fisici sono essenzialmente esplosioni ormonali, ma non solo quelli fisici…
… hormonal increase… also influence the expression of a wide range of social, behavioral, and sexual differences (Hayward, 2003). As examples, the hormonal changes influence the emergence of sexual fantasy… For boys, there is a marked increase in sexual behavior, especially masturbation…
Nel corso dell’infanzia le differenze fisiche e comportamentali tra bambini e bambine sono ridotte ma già presenti. La fase successiva è sostanzialmente un’amplificazione di queste differenze…
… During childhood there are small to moderate differences favoring boys in tasks such as grip strength, jumping distance, and running speeds, with large differences emerging during adolescence (Thomas & French, 1985); by 17 years of age, more than 9 out of 10 boys outperform the average girl in these areas…
Le differenze fisiche si traducono poi in una maggior forza e in dimensioni più ampie nel maschio…
… As a result of the sex difference in leg length, muscle mass, and cardiovascular capacity, men can run faster, on average, than women (Deaner, 2006). By far, the largest differences in physical competencies are for throwing distance and throwing velocity (Thomas & French, 1985)…
Lo scheletro maschile diventa più adatto al lancio di oggetti…
… The sex differences in throwing skills are related to differences in the structure of the supporting skeletal system. Relative to overall body height, boys have a longer ulna and radius (i.e., forearm), on average, than do girls (Gindhart, 1973)….
Ci sono almeno due ipotesi in campo per giustificare una simile differenziazione: 1) competizione sessuale (i maschi competono tra loro in modo più feroce) e 2) specializzazione nei compiti (l’uomo caccia, la donna cura i bimbi e raccoglie)…
… some theorists have argued that the physical differences evolved from the division of labor, including men’s hunting, rather than male–male competition (e.g., Kolakowski & Malina, 1974)…
Alcuni indizi privilegiano la prima ipotesi…
… Across polygynous primates with intense male–male competition, there is a characteristic pattern of female and male growth…
Alcuni tratti femminili (per esempio le dimensioni ampie della regione pelvica) ci ricordano che la selezione sessuale (e non solo quella naturale9 è all’opera…
… Of course, some physical sex differences, such as the wider pelvic region in women, have evolved through natural rather than sexual selection. Once the large pelvis evolved, the waist-to-hip ratio that men find attractive emerged and began to be shaped by male choice…
Lo scheletro femminile è più flessibile (si muove meglio in spazi ridotti) e il colpo d’occhio ravvicinato più reattivo…
… Girls are also more physically flexible than boys and have an advantage in fine eye–motor coordination…
La manipolazione “sottile” sembra migliore nelle donne…
… Kimura (1987) argued that the advantage of girls and women might be related to manipulating objects “within personal space, or within arm’s reach, such as food and clothing preparation and child care” (p. 145)…
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Nella fase infantile i bambini sono più vulnerabili delle bambine, il loro metabolismo è più dispendioso e in caso di scarsità di risorse soffrono di più…
… Related to the need to grow larger and stronger than girls is slower growth, beginning prenatally: Boys are born “premature” relative to girls. They have higher activity levels and higher basal metabolic rates than girls, resulting in higher caloric requirements for normal development…
Inoltre, nei giochi, prendono più rischi e si feriscono più di frequente…
… Among other social and behavioral sex differences is higher risk taking and accidental injury in boys…
La loro salute è più esposta e risentono di più in caso di malnutrizione…
… boys will be more sensitive—suffer more physical, social, and cognitive deficits—than girls when growing up in poor conditions, including poor nutrition, inadequate health care, or poor social stimulation…
Quando le condizioni ambientali non sono ottime sono i maschietti a risentirne: la loro mortalità è più accentuata…
… An analysis of 16,000 infant deaths in the United States between 1983 and 1987, inclusive, revealed that boys had a 38% higher mortality rate due largely to infectious disease during the 1st year of life (J. S. Read, Troendle, & Klebanoff, 1997)…
Le diseguaglianze sociali incidono di più sul benessere dei maschietti…
… Poor early physical development, exposure to parasites, frequent illness, poor nutrition, and inadequate social and cognitive stimulation have been shown to be related to poor long-term cognitive, academic, and social outcomes, even after controlling for SES and other confounds (S. P. Walker, Chang, Powell, & Grantham-McGregor, 2005). Sex differences are not typically reported in these studies, but boys’ risk of poor early growth and development is likely to result in an overrepresentation of boys and men with poor long-term outcomes…
La qualità dell’allattamento e la disponibilità di “giunte” è importante per tutti, ma lo è di più per i bambini che per le bambine…
… Breast-fed infants of both sexes had normal IQ scores at age 8 years… For the two groups that were not breast fed, the risk of cerebral palsy or other significant cognitive impairments was 5 to 6 times higher for boys who received standard formula compared with boys who received the supplement. The risk was not elevated for girls. In fact, the mean IQ of girls was in the average range and did not vary across conditions…
Un ambiente arricchito e una società prospera è quindi un vantaggio soprattutto per i maschietti. Sono loro i maggiori beneficiari di una condizione infantile oggi molto migliore…
… The flip side of boys’ greater vulnerability may be an enhanced potential to benefit more than girls from an enriched environment. This hypothesis has not been tested, although there were hints of such an effect in the Lucas et al. (1998) study…
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I maschietti sono più attratti dalle cose, le femminucce dalle persone. La diversa preferenza sembrerebbe dipendere dagli ormoni…
… M. Alexander (2003) hypothesized that some of the early sex differences in orientation toward people (more in girls) or things (more in boys) reflect the evolved skeletal structure of the visual system, specifically, biases in the what and where visual pathways. Prenatal and early postnatal exposure to androgens may enhance development of the latter and result in attentional and perceptual biases for processing spatial location and object motion…
Le ragazze si concentrano sulle persone, il loro contatto visivo è più frequente e prolungato…
… Orientation toward other people is measured in terms of the duration of eye contact, empathy for others’ distress, and time spent looking at faces, among other behaviors…
La cosa è già riscontrata nel primo giorno di vita…
… “there is no doubt that girls and women establish and maintain eye contact more than boys and men. The earliest age for which this is reported is one day”… The sex difference in time spent looking at the face was small but consistent with studies of older infants (McClure, 2000)…
Le ragazzine hanno più memoria per i volti…
… By this age, girls might also have a better memory for faces and might be more skilled in discriminating two similar faces (e.g., J. F. Fagan, 1972)…
I maschi si curano più del gruppo, le femmine della relazione binaria…
… sex difference in social organization will manifest in the attentional interests of boy (i.e., a focus on groups) and girl (i.e., a focus on individuals) infants…
Le differenze nell’empatia sviluppata dai due sessi sono già evidenti nella prima infanzia…
… Infant girls may react with greater empathy than infant boys to the distress of other people (M. L. Hoffman, 1977). Simner (1971) found that infant girls cried longer than infant boys when exposed to the cry of another infant, but there was no sex difference in reflexive crying when the infants were exposed to artificial noise of the same intensity…
Nel rapporto con i genitori le bambine hanno una marcia in più…
… Studies of the quality of social interactions between parents and infants also reveal that girls are more responsive, and perhaps more sensitive, to social cues than boys (Freedman, 1974; Gunnar & Donahue, 1980; W. D. Rosen, Adamson, & Bakeman, 1992)… In a related study with 6- to 12-month-olds, Gunnar and Donahue (1980) found that mothers were just as likely to attempt to initiate social interactions with their sons as with their daughters, but daughters were much more responsive; Whiting and Edwards (1988) reported the same pattern with older children across cultures…
Il contatto visivo madre-figlia non ha paragoni…
… K. A. Buss, Brooker, and Leuty (2008) found that 2-year-old girls sought contact with and stayed closer to their mother than did boys in a fear-eliciting situation… In an intensive naturalistic study of mother–infant interactions from birth to 3 months, Lavelli and Fogel (2002) found that girls spent more time in face-to-face communication with their mothers than did boys….
I maschietti sono attratti dalla forma, dal colore e dal movimento meccanico degli oggetti. La differenza è ancora maggiore rispetto a quella riscontrata nella sensibilità ai volti…
… In an intensive naturalistic study of mother–infant interactions from birth to 3 months, Lavelli and Fogel (2002) found that girls spent more time in face-to-face communication with their mothers than did boys….
Riassumendo…
… Males appear to be more likely to store information about the various components of a repeatedly presented stimulus, for example, its form and color …. [while] females, unlike males, are more likely to store information about the consequences of orienting. (p. 382)…
Queste differenze sono correlate con l’esposizione prenatale al testosterone…
… Baron-Cohen and his colleagues have been studying how prenatal exposure to testosterone influences sex differences in infancy and in older children (Baron-Cohen, Lutchmaya, & Knickmeyer, 2004; Lutchmaya, Baron-Cohen, & Raggatt, 2002a, 2002b)… Testosterone gets into the amniotic fluid by diffusion through the fetus’s skin and through urination…
Testosterone e contatto visivo…
… Lutchmaya et al. (2002a) examined the relation between prenatal testosterone levels and the frequency with which 12-month-olds made eye contact with their mother… Prenatal testosterone levels were, however, related to how often the boys made eye contact but not in a straightforward way…
Testosterone e linguaggio…
… Lutchmaya et al. (2002b) assessed the vocabulary of boys and girls at 18 and 24 months. At 18 months, the vocabulary of girls was more than double that of boys. At 24 months, the typical girl knew 40% more words than did the typical boy. At this age, higher prenatal testosterone levels were associated with lower vocabulary scores…
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Bambini e bambine giocano diversamente, è un dato universale…
… sex differences in play activities are a universal aspect of children’s behavior…
A sei mesi il sessismo dei bambini è già notevole…
… Infants begin to make sex-based discriminations (e.g., between male and female voices) as early as 6 months of age (C. L. Martin, Ruble, & Szkrybalo, 2002). By 18 months, they are beginning to categorize some activities as male typical and others as female typical (Eichstedt, Serbin, Poulin-DuBois, & Sen, 2002), and they talk about these as 2-year-olds (S. A. Gelman, Taylor, & Nguyen, 2004)…
I bambini piccoli hanno molti più stereotipi di genere dei loro genitori…
… children are often more stereotyped than their parents and other adults (e.g., S. A. Gelman et al., 2004)…
Un genitore puo’ togliere alcuni stereotipi alla prole ma difficilmente cambia i loro comportamenti effettivi…
… Girls and boys segregate into same-sex groups whether or not they are engaging in sex-typed activities (Maccoby, 1988), and children raised by egalitarian parents—those who actively discourage sex typing—have less stereotyped beliefs about sex differences than do children raised in other types of families, but their toy and play preferences are the same as these other children (Weisner & Wilson-Mitchell, 1990)…
I bambini giocano alla lotta, le bambine alla mamma. Il dato è universale…
… Rough-and-tumble play is more common among boys and play parenting is more common among girls… The sex difference in rough-and-tumble play emerges by age 3 years… This sex difference is found in all modern societies…
Quanto più i bambini vengono lasciati liberi (assenza di un adulto supervisore), tanto più hanno comportamenti e preferenze stereotipate…
… The sex difference is most evident with groups of three or more children and in the absence of adult supervision…
I ragazzini nutrono un maggior interesse per il gruppo…
… The sex difference in infants’ interest in groups (Benenson et al., 2004) continues into childhood and beyond. These studies confirm that boys organize themselves into much larger social groups than do girls, engage in intergroup competition once such groups are formed, form within-group dominance hierarchies, and show within-group role differentiation and specialization when engaged in group-level competition (Eder & Hallinan, 1978; Lever, 1978)… More often, boys compete as members of teams and must simultaneously coordinate their actions with those of their teammates while taking into account the action and strategies of their opponents…
Tra giochi, ormoni e stereotipi esiste una forte correlazione…
… Collaer and Hines (1995) concluded that the “clearest evidence for hormonal influences on human behavioral development comes from studies of childhood play. Elevated androgen in genetic females …is associated with masculinized and defeminized play” (p. 92)…
Qui i soggetti sperimentali più preziosi sono quelle bambine esposte a livelli ormonali vicini a quelli maschili…
… excess levels of androgens (i.e., affected by congenital adrenal hyperplasia [CAH])…
In effetti, i comportamenti di queste bambine si avvicinano a quelli maschili…
… In an observational study, Hines and Kaufman (1994) found that girls affected by CAH engaged in more playful physical assaults, physical assaults on objects, wrestling, and rough-and-tumble play in general than did unaffected girls, but none of these differences were statistically significant…
Le bambine amano giocare alla mamma. Il dato è uniforme in tutte le culture…
… Throughout the world, girls are assigned child-care roles, especially for infants, more frequently than are boys (Whiting & Edwards, 1988). Girls also seek out and engage in child care, play parenting, and other domestic activities (e.g., playing house) with younger children or child substitutes such as dolls more frequently than do same-age boys (Pitcher & Schultz, 1983)…
E’ comune anche alle culture antiche e agli altri primati…
… In sum, a sex difference in play parenting favoring girls is found in both modern and traditional societies and in fact most other species of primate (Eibl-Eibesfeldt, 1989; Nicolson, 1987)…
E per quanto riguarda i giochi esplorativi e itineranti?
In quasi tutte le società l’uomo si muove e viaggia di più…
… Across traditional societies, men travel farther from the home village than do women for many reasons, including finding mates, developing alliances with the men of neighboring villages, hunting, and intergroup warfare (Chagnon, 1997; K. Hill & Hurtado, 1996; K. Hill & Kaplan, 1988)… Women’s foraging, in contrast, typically occurs within the group’s territory… Unlike women’s foraging for fruit or tubers, hunting requires an ability to track and predict the movements of evasive prey, human and nonhuman…
In genere nei giochi maschili si occupa più spazio, si compete e si corre di più…
… The sex difference is related in part to the sex difference in group-level competitive play and to a greater engagement of boys than girls in solitary running (Eaton & Enns, 1986; Lever, 1978)… During juvenility and beyond, boys have a larger play range than girls…
Nei giochi maschili si esplora e si manipola la natura con maggior frequenza…
… Whenever it emerges, boys not only engage in more locomotor activities over a larger range than girls but also explore and manipulate (e.g., build things, such as forts) the ecology much more frequently (Matthews, 1992)…
I maschi hanno maggior facilità nel farsi delle mappe mentali del territorio…
… ecological exploration is correlated with the ability to generate mental maps of the physical layout of the ecology but is not consistently related to other forms of spatial cognition, such as the ability to copy geometric figures (R. H. Munroe et al., 1985)…
E anche nel risolvere problemi che coinvolgono la dimensione spaziale…
… Scientists do know that 4-year-old boys, and perhaps even infant boys (D. S. Moore & Johnson, 2008; Quinn & Liben, 2008), have an advantage over same-age girls on some spatial tasks (Levine, Huttenlocher, Tayler, & Langrock, 1999) and that this advantage grows during juvenility, puberty, and adolescence (Matthews, 1992; D. Voyer, Voyer, & Bryden, 1995)…
Questa differenza nelle abilità scompare tra i bambini delle famiglie disagiate…
… Levine et al. assessed 547 children from high-, middle-, and low-income backgrounds across second and third grades on two spatial tasks—map reading and two-dimensional mental rotation—and a syntax comprehension test. No sex differences were found on the syntax test, but boys from high- and middle-income families had an advantage on both spatial tasks. There was no sex difference on either spatial task for children from low-income families. In other words, low family income was associated with lower scores for both boys and girls on all three tests…
I maschietti amano giocare con gli oggetti…
… Boys engage in much more object-oriented play than do girls (Eibl-Eibesfeldt, 1989; Freedman, 1974; Sandberg & Meyer-Bahlburg, 1994; Sutton-Smith et al., 1963)…
Talune differenziali nelle abilità derivano direttamente da questa attitudine…
… An analysis of the relation between the focus of play activities and the pattern of cognitive abilities indicated that children whose play was object oriented “performed better on tests of ability to organize and classify physical materials” (Jennings, 1975, p. 515), as assessed by tests of spatial cognition (e.g., the ability to mentally represent and manipulate geometric designs) and the ability to sort objects on the basis of, for example, color and shape…
Anche le differenze vocazionali sono interessate…
… As I review elsewhere (Geary, 1998b), there are sex differences in interest in and pursuit of careers that involve designing and working with mechanical objects, as in engineering and computer technology…
Altre evidenze del discrimine…
… Chen and Siegler (2000) found that as early as 18 months of age, boys have small to moderate advantages over girls in several aspects of early tool use, as in using a hooked stick to retrieve a desired toy. Boys were better at applying tool-related knowledge learned in one setting to another setting, were more consistent in the use of tools across settings, and were more successful in the use of tools in problem solving. Without any hints from an adult, 79% of the boys and 31% of the girls were able to use such tools to retrieve the toy…
Ci sono poi i giochi di ruolo. I ruoli preferiti da maschi e femmine sono molto diversi…
… Both boys and girls regularly engage in sociodramatic play but differ in the associated themes and the roles they tend to adopt, as noted by Pitcher and Schultz (1983): Boys play more varied and global roles that are more characterized by fantasy and power. Boys’ sex roles tend to be functional, defined by action plans. Characters are usually stereotyped and flat with habitual attitudes and personality features (cowboy, foreman, Batman, Superman). Girls prefer family roles, especially the more traditional roles of daughter and mother. Even at the youngest age, girls are quite knowledgeable about the details and subtleties in these roles …. From a very early age girls conceive of the family as a system of relationships and a complex of reciprocal actions and attitudes. (p. 79)…
