Male rh = 1442g (n=7), callosal area 672 mm^2 • Male MH (n=5) 1511g, 801 (differs sign from Male RH) • Females RH (n=20) 1269g, 655 • Fem MH (n=10), 1237g, 697 (differs from fem RH)
Absolute vs Relative Size Differences • Bermudez & Zatorre (2001, n=137) found larger splenium (back of corpus callosum) in females.
FEMALES • Larger language areas -Harasty et al, 1997 • Larger lateral frontal area – Schlaepfer et al, 1995 • More densely packed neurons in temporal lobe, Witelson et al 1995 • MALES • Larger medial frontal, Goldstein et al, 2001 • Larger cingulate, Paus et al 1996 • Larger amygdala and hypothalamus, Swaab et al, 1985 • More white matter volume, Gur et al, 1999 • More neurons overall, Pakkenberg & Gunderson, 1997
Reliable Functional Sex Differences • Men are better at • Visuospatial tasks • Higher mathematics • Aggression • Females are better at: • Verbal tasks Hemispheric asymmetries may be less marked in females compared to males
APHASIAS occur most often in women with LH anterior damage. In men, they occur more frequently with LH posterior damage. • APRAXIA, or difficulty in selecting hand movements, is associated with LH frontal damage in women and with LH posterior damage in men.
Functional Neuroimaging Differences • EEG males more asym – Corsi-Cabrera et al, 1997; MEG Reite et al, 1995
Gender differences VHS: Brain Sex #1 (Anything you…)
Problem-Solving Tasks Favoring Women • Women tend to perform better than men on tests of perceptual speed, in which subjects must rapidly identify matching items for example, pairing the house on the far left with its twin
In addition, women remember whether an object, or a series of objects, has been displaced
On some tests of ideational fluency, for example, those in which subjects must list objects that are the same color, and on tests of verbal fluency, in which participants must list words that begin with the same letter, women also outperform men
Women do better on precision manual tasks-that is, those involving fine-motor coordination-such as placing the pegs in holes on a board:
Problem-Solving Tasks Favoring Men • Men tend to perform better than women on certain spatial tasks. They do well on tests that involve mentally rotating an object or manipulating it in some fashion, such as imagining turning this three-dimensional object
or determining where the holes punched in a folded piece of paper will fall when the paper is unfolded:
Men also are more accurate than women in target-directed motor skills, such as guiding or intercepting projectiles:
They do better on disembedding tests, in which they have to find a simple shape, such as the one on the left, once it is hidden within a more complex figure:
And men tend to do better than women on tests of mathematical reasoning:
Cognitive behavior • MOTOR • Target throwing & catching M>F Hall & Kimura, 1995 • Fine motor skills F>M Nicholson & Kimura, 1996 • SPATIAL • Mental rotation M>F Collins & Kimura, 1997 • Spatial navigation M>F Astur et al, 2002 • Geographical knowledge M>F Beatty & Troster, 1987 • Spatial memory F>M McBurney et al, 1997 • MATH APTITUDE • Computation F>M Hyde et al, 1990 • Mathematical Reasoning M>F Benbow, 1988 • PERCEPTION • Sensory sensitivity F>M Velle, 1987 • Perceptual speed F>M Majeres, 1983 • Facial/Body expression F>M, Hall 1984 • Visual Recognition memory F>M McGivern et al, 1998 • VERBAL • Fluency F>M Hyde & Linn, 1988 • Verbal Memory F>M McGuinness et al, 1990
Mechanism(s) responsible for Gender Differences • Interhemispheric: Females have greater callosal connectivity • Intrahemispheric: Language organization differs by gender • Strategic: Females employ verbal strategies more often (even for spatial tasks) • Mediated: Difference due to other trait variables such as handedness, familial hand, cognitive style, maturation, hormonal!)
TESTOSTERONE LEVELS • On a test in which women usually excel (bottom), no relation is found between testosterone and performance.
LDT With Distractors TARGET + (DISTRACTER)
LDT with Distractors + park stop
Lexical Decision Results: Example of Treatment Effects Post NF + Pre -
Within Condition + Nonsense (nonverbal) Shapes