The Male Brain (19 page)

testosterone as in an adult man
: For more on the infantile, or perinatal, masculinization of adult sex behavior, see Wu 2009, Wudy 1999, and Wright 2008.

exploratory behavior and rough play
: Wang P. 2009 found that boys older than one year have very low levels of testosterone, but they continue to have high MIS until the onset of puberty.

when she's angry or afraid
: Peltola 2009 found that an enhanced sensitivity to facial signals of threat emerges between five and seven months of age. This may reflect functional development of the brain mechanisms involved in processing of emotionally significant stimuli. Grossman 2007 found that seven-month-olds integrate emotional information across modalities and recognize common emotions in the face and voice. For more on brain processing of words, faces, and emotions, see Schacht 2009. For more on infant gazing at objects and adult emotional expressions, see Hoehl 2008.

and can easily ignore them
: Rosen 1992. They found that by the age of twelve months, the intensity of the mothers' fear signals increased and were more intense toward boys, but boys ignored them more. For overview, see Maccoby 1998, Mumme 1996, and Becker 2008b.

For girls, the opposite happens
: Researchers find that by one year of age, girls are more socially oriented toward their mothers than are boys; see Wasserman 1985, Maccoby 1998, and Byrd-Craven 2007. They are more wary than boys, according to Jacklin 1983 and Gunnar 1984. Zahn-Waxler 1992 found that infant boys cry less than girls in response to hearing the distressed cries of another baby. By twelve to twenty months, boys are less interested in seeking out and inquiring about the distress of someone who is hurt; for overview see Byrd-Craven 2007 and Leppanen 2001. Even as children get older, studies show that what is important to girls and boys, and meaningful to pay attention to, is different in terms of nonverbal emotional communications. For overview of sex-difference brain research, see Becker 2008b.

of warning on Jessica's face
: For boys ignoring their mothers more, see Rosen 1992 and Maccoby 1998.

in the room with them
: Rosen 1992 in "An experimental investigation of infant social referencing: Mothers' messages and gender differences." For more on gender differences in brain and behavior, see Maccoby 1998, Byrd-Craven 2007, Eme 2007, and Becker 2008b.

at the risk of punishment
: Cialdini 1998a.

 

sons as to their daughters
: Maccoby 1998.

take risks and break rules
: Maccoby 1998. For more on sex differences in play behavior, also see Minton 1971 and Berenbaum 2008.

many mothers wince, including me
: A mother's reaction to a boy's genitals may have a bigger effect than is commonly acknowledged, even in other mammals. Wallen 2009 found that in primates, maternal increased responsiveness to boys is best accounted for by the mother's reactions to the penis of her offspring.

are "girl colors" like pink
: Feiring 1987 and Fagot 1985. For overview of girls' and boys' toys, see Pasterski 2005 and Hassett 2008.

destroying, and seeking new thrills
: Maccoby 1998. For more on the brain and boys' thrills, see Byrd-Craven 2007, Manson 2008, and Becker 2009.

more interested in cooperative games
: Berenbaum 2008. McClure 2000 found that during the late preschool and early school years, girls tend increasingly to play in small, intimate groups, whereas boys more typically form large, hierarchically organized groups focused on competition. For overview of children's gender cultures, see Sheldon 1996 and Maccoby 1998. Charlesworth 1987 found that girls got greater access to the toys by verbal bargaining rather than through physical pushing like the boys.

while girls spend only 35 percent
: Lever 1976.

 

twenty times more often than boys
: Maccoby 1998.

 

to use as toy guns
: Maccoby 1998.

 

and used beans as bullets
: Sheldon 1996 and Maccoby 1998.

is being called a girl
: Blaise 2005 found that in early childhood classrooms, being called a "girl" is considered by boys to be one of the most shameful, polluting, and degrading insults of all.

like girls' games and toys
: Feiring 1987 found that boys reject other boys who like girls' games and toys.

and must therefore be avoided
: Feiring 1987 says that even in the years before exclusionary same-sex play, groups evolved in several studies of children 24 to 36 months old, where boys were able to identify their own sex's toys and activities better than girls did. For more on self-imposed sex segregation, see Pasterski 2005 and Maccoby 1998.

doll and the wheeled toy
: Hassett 2008.

 

toys more than other girls
: Servin 2003.

muscle groups when they play
: Hassett 2008. Eaton 1986 says that boys' toys reflect their preference for using big muscle groups when they play, and sports reflect boys' preference for gross motor behavior and propulsion--of themselves and objects--from infancy onward. For overview of gendered play, see Berenbaum 2008.

like car and plane crashes
: Iijima 2001 found that drawings by boys and girls showed clear sex differences. Girls tended to draw human figures, mainly girls and women, as well as flowers and butterflies. Girls used bright colors, such as red, orange, and yellow, and their subjects tend to be peaceful and arranged in a row on the ground. Boys, however, preferred to draw more technical objects, weapons, and fighting, and means of transport, such as cars, trains, and airplanes, in bird's-eye-view compositions and in dark, cool colors, such as blue. See also Tuman 1999 on children's gendered art.

is to determine social ranking
: Archer 2006.

 

seen the humor in it
: DiPietro 1981.

 

break his sense of self
: Eaton 1986.
"have their kind of fun"
: Maccoby 1998.

form of a dopamine rush
: Becker 2008b says that sex differences in the regulation of dopamine, DA, in the brain's ascending mesolimbic projections may underlie sex differences in motivation and result in the expression of differences in motivated behaviors between boys and girls, men and women.

and children self-impose sex segregation
: Maccoby 1998.

mock-fight frequently; girls do not
: Maccoby 1998. Also see Eme 2007, Flanders 2009, and Becker 2008a on sex differences in motivation.

if they placed at all
: Grant 1985.

 

the girls did not show
: Feiring 1987.

 

establish physical and social dominance
: Eme 2007 and Becker 2008b.

 

"most important thing to be good at"
: Boulton 1996.

 

of the six-month study
: Edelman 1973 and Weisfeld 1987.

 

levels than did the other boys:
Weisfeld 1987.

 

the hierarchy at age fifteen
: Weisfeld 1987.

of learning boys do differently
: See Benenson 2003 and 2009 for more on boys' choosing to ally with stronger peers, and for more on girls' need to maintain conflict-free friendships.

Wii had become their favorite toy
: Hoeft 2008 found that these gender differences may help explain why males are more attracted to and more likely to become hooked on video games than females. For more on computer game playing and improving spatial skills, see De Lisi 2002, Feng 2007, Ginn 2005, Olson 2007, Heil 2008, and Wolbers 2006.

brain linked to dopamine production
: Hoeft 2008 found that males showed greater activation compared to females in the mesocorticolimbic areas--which may account reward prediction, learning reward values, and cognitive state during computer video games. For more on the male brain and dopamine, see Lavranos 2006 and Becker 2008b.
system--dopamine brain

for gender differences in

 

even if he isn't moving
: Grafton 1997.

control his own jumping muscles
: Orzhekhovskaya 2005 found males have more activity in neurons in the motor areas of the brain. See Cherney 2008 on "Mom let me play more video games."

girls do in this way
: For more on the gender difference in movement biology, see Field 2008.

and express themselves as well
: Ehrlich 2006 found that the boys frequently gestured about movement even when they did not talk about it; they found that gesture (but not talk) was associated with successful performance on spatial transformation tasks. Boys used their hands and body to convey an understanding of the spatial transformation task not found in their spoken explanations. And for more on girls catching up to boys on visuospatial tasks by practicing video games, see Feng 2007, who found that playing an action video game can virtually attention disparity in mental rotation ability. For more on sex differences in movement and the brain, see Field 2008, Hampson 2008, Spence 2009, and Becker 2009. eliminate the gender difference in spatial

and simultaneously decrease the gender

the meaning of that word
: For more on embodied cognition, see Siakaluk 2008, Thomas 2009, and DeCaro 2009. See Ullman 2008 for more on sex differences in the neurocognition of language.

their advantage at spatial manipulation
: Keller 2009 found evidence for gender differences in the functional and structural organization of the right-hemisphere brain areas involved in mathematical cognition. Spence 2009 found that women can catch up to men on spatial skills by practicing single-shooter video games.

object in their mind's eyes
: Hahn 2009. Also see Koscik 2009, Hampson 2008, Hugdahl 2006, and Clements-Stephens 2009 for more on mental rotation.

differences between boys and girls
: Scientists agree that there are genuine between-sex differences in cerebral activation patterns during mental rotation activities even when performances are similar and that the sexes use different strategies in solving mental rotation tasks. Clearly males and females can both generate male-and female-typical behaviors, but their brains use different strategies to do so. For structural differences in the brain related to visuospatial abilities and language, see Hanggi 2009, Shaywitz 1995, Jordan 2002, Piefke 2005, Neuhaus 2009, and Hampson 2008.

them to grasp its three-dimensionality
: Scientists believe that sex effects reflect a difference in strategy, with females mentally rotating the polygons in an analytic, piecemeal fashion and males using a holistic mode of mental rotation. See Yu 2009, Heil 2008, Schoning 2009, and Hooven 2004 on testosterone and mental rotation.

explanation without using any words
: Ehrlich 2006 found that before training, the response for the boys was to produce answers in movement and gesture on all eight problems; however, the response for the girls was to produce answers in movement and gesture on zero of the eight problems. After "gesture-training," the girls did much better. For further reading on gesturing and math teaching, see Goldin-Meadow 2009. For more on movement and math, see Broaders 2007, Terlecki 2008, Thomas 2009, Lorey 2009, Thakkar 2009, and Munzert 2009.

without intervention, use them differently
: See Hampson 2008 for more on sex differences in visuospatial cognition and learning. For more studies that found sex differences in brain circuits used for mental rotation, see Nuttall 2005, Casey 2001, Jordan 2002, Peters 2006, Quaiser-Pohl 2002, and Parsons 2004.

amounts of the pheromone androstenedione
: Hummel 2005. And see Larsen 2003 on the dramatic hormonal changes that begin before the body changes of puberty.

TWO: THE TEEN BOY BRAIN

different from the preadolescent brain
: Yurgelun-Todd 2007 found emotional and cognitive changes during adolescence. Brain regions that underlie attention, reward evaluation, impulses,
architectural early adulthood. emotional discrimination, inhibition of and goal-directed behavior undergo

remodeling throughout puberty and into

little androgen switches
: Swaab 2009 found that certain areas of the male brain have more receptors for testosterone, i.e., androgen receptors, AR, than the same areas of the female brain at birth but await its maximum behavioral activation at puberty testosterone production from the 2010 found that the onset of puberty in males and females is controlled differently. Testosterone levels rise at puberty, and these levels support mating and aggressive behavior. And not until males are required to care for with the surge in testicles. Kauffman offspring, or until old age, does their testosterone level decrease. For more on testosterone and the male brain, see Matsuda 2008, Wu 2009, Sato 2008, Neufang 2009, Becker 2008b, Ciofi 2007, Zuloaga 2008, Shah 2004, and Schulz 2006 and 2009.

many other boys his age
: Christakou 2009 found in teens a recruitment of age-correlated prefrontal, PFC, activation in females, and of age-correlated parietal activation in males, during tasks of cognitive control. Perrin 2009 and Giedd 1996 and 2006 found that brain development in teens differs between boys and girls, reaching its peak in girls one to two years earlier than in boys.