Irwin Silverman

The Hunter-Gatherer theory of spatial sex differences: Proximate factors mediating the female advantage in recall of object arrays

Abstract Based on their theory that sex differences in spatial abilities originated in human evolution as a function of division of labor, Silverman and Eals (1992) demonstrated in a series of studies that females consistently surpassed males in recall of locations of objects in a spatial array. The present studies were replications of the above, but with the inclusion of uncommon objects, for which subjects would not possess verbal labels. Female superiority for recall of locations of common objects as observed in Silverman and Eals was replicated across incidental and directed learning conditions. The female advantage occured as well for uncommon objects, but only under incidental learning conditions. Conjectures are offered regarding sex differences in attentional and imagery processes that could account for this pattern of results.

Effects of estrogen changes during the menstrual cycle on spatial performance

Abstract Four sequential, interrelated studies of the relationship of menstrual cycle phase to three-dimensional mental rotations performance were conducted, using both between-and within-subjects designs. All studies showed significant increases in mean mental rotations scores during the menstrual period phase, when estrogen levels were at their lowest. Effects occurred only for mental rotations; relationships with hormonal status did not occur for control tests, which were not of a spatial nature, and a different spatial test (Space Relations). Findings are discussed as they relate to ontogenetic development and evolutionary origins of sex-specific differences in spatial behaviors.

Testosterone levels and spatial ability in men

Testosterone (T) levels were measured by salivary assays in 59 males at times of the day when T was expected to be highest and lowest. Relationships were evaluated for mean hormone levels across the two sessions and hormone level changes between sessions with performance on three-dimensional mental rotations, a spatial test which customarily favours males. An anagrams task and the digit symbol test were used as controls. Mental rotations scores showed a significant positive relationship with mean T levels but not with changes in T. There were no significant relationships between control test scores and mean T levels. Findings are discussed in terms of their contributions to the resolution of ambiguities in prior reported data.

Differences in the Relationship of Menstrual Cycle Phase to Spatial Performance on Two- and Three-Dimensional Tasks ☆ ☆☆

Inverse activational effects of estrogen on spatial problem-solving performance in females have been amply demonstrated, although the findings across studies are somewhat inconsistent. In an attempt to resolve this ambiguity, the present study compared activational effects, using phases of the menstrual cycle as the criteria for estrogen levels, on two- and three-dimensional spatial tasks. As predicted, menstrual cycle effects were obtained for the latter category only. Results were interpreted as a function of the greater ecological validity of three-dimensional tasks.

SEX RELATED FACTORS IN THE PERCEPTION OF THREATENING FACIAL EXPRESSIONS

This study replicated and extended previously reported sex differences involving both viewer and target in the recognition of threatening facial expressions. Based on the assumption that the evolved cognitive mechanisms mediating anger recognition would have been designed by natural selection to operate quickly in the interests of survival, brief tachistoscopic presentation of stimulus photographs was used. Additionally, in contrast to prior published studies, the statistical methods of signal detection research were used to control for the confounding effects of non-random guessing. The main hypothesis, that anger posed by males would be more accurately perceived than anger posed by females, was supported. A secondary hypothesis, that female-posed anger would be more accurately perceived by women than by men, received partial support. Testosterone levels, measured inferentially in terms of diurnal cycles, failed to show the hypothesized positive relationship to accuracy of anger perception.

Processes underlying sex differences in route-learning strategies in children and adolescents

Cognitive processes underlying sex differences in route-learning strategies were investigated in children and adolescents using a direction-giving paradigm based on a novel map. Sex differences in object memory and spatial perception tasks were found in children as young as 9 years of age although differences in route-learning strategies did not emerge until 12 years of age. This was followed by sex-specific patterns of cognitive processes underlying route-learning strategies in adolescents, suggesting that route-learning strategies emanate from different spatial processes. Results are consistent with the notion of specialized spatial processes in males and females, presumed to be the products of differential evolutionary pressures related to the division of labour.

Early proximity and intimacy between siblings and incestuous behavior: A test of the Westermarck theory

Abstract This study was based on the Westermarck hypothesis, which maintains that the proximate mechanism for sibling incest avoidance is continued proximity in early childhood. Using a survey method, we compared university students reporting sibling incest with a matched sample of those reporting no such experience on measures of both early intimacy of the sibling pair (e.g., sleeping arrangements, practices regarding nudity) and early separations between them. Intimacy variables did not relate to incestuous behavior. Separation for more than a year during the first six years was significantly related to sexual activities which culminated in anal, oral, or attempted or actual genital intercourse (labeled consummatory behaviors), but this difference in regard to nonconsummatory sexual activities was in the opposite direction. It was suggested that previous interpretations of the Westermarck effect implying that early cohabitation produces sexual disinterest may require revision. Early association may function instead to provide a barrier to more mature, consummatory sexual activities and, hence, reduce procreative potential.

Early separation and sibling incest: A test of the revised Westermarck theory

This was a follow-up study of earlier reported findings by the present investigators suggesting, albeit equivocally, that separation during early childhood inhibited later sexual acts of a potentially procreative nature between siblings but did not deter other sexual activity. The present study surveyed 170 subjects, mostly in the Toronto area, by telephone and mail. Respondents reporting potentially procreative, postchildhood sexual acts (attempted or completed genital intercourse) with siblings were compared with those reporting sexual relationships excluding procreative acts, and a third sample reporting no postchildhood sibling sexual behavior. Consonant with expectations from the earlier study, prolonged separation during early childhood was associated with procreative postchildhood sexual activity but not with other postchildhood sexual activity. Contrary to predictions, however, both sexual activity groups reported significantly more nudity and physical contact with siblings during childhood than subjects reporting no sexual activity. The findings are discussed in terms of a revised version of the Westermarck hypothesis, which is consistent with a domain-specific approach to evolved incest avoidance mechanisms.

Homogeneity of Effect Sizes for Sex across Spatial Tests and Cultures: Implications for Hormonal Theories

Japanese and Canadian samples were compared on two spatial test which typically show higher male scores but tend to differ in the magnitude of the sex difference. Sex differences, both in terms of direction and magnitude, were similar between cultures. Results are discussed in terms of their relevance for hormonal theories of spatial sex differences.

The relationship between testosterone and route-learning strategies in humans☆

The relationships between route-learning strategies and circulating testosterone and estradiol levels were investigated in men and women. Testosterone and estradiol concentrations were measured by salivary assays and route-learning strategies were assessed using a direction-giving paradigm based on a novel map. Testosterone was positively correlated with the use of male-biased route-learning strategies in men, but not in women. These findings suggest sex-specific patterns of relationships between circulating testosterone and spatial processing, which apply to everyday spatial behavior.