Individual differences are explicitly connected to social interaction in Darwin's notion of sexual selection. Traits that increase the probability of successful reproduction will tend to increase in frequency. This process operates partly through differential choice, by one sex, of certain traits in the other. According to the parental investment model, females frequently have more stringent criteria for the traits they will accept in a mate because they have a relatively larger investment in each offspring. Because human mating arrangements often involve a substantial commitment of resources by the male, it is necessary to invoke a distinction between the selectivity involved during casual mating opportunities and the selectivity exercised when choosing a long-term partner. Ninety-three undergraduate men and women rated their minimum criteria on 24 partner characteristics at four levels of commitment. In line with an unqualified parental investment model, females were more selective overall, particularly on status-linked variables. In line with a qualified parental investment model, males' trait preferences depended upon the anticipated investment in the relationship. Males had lower requirements for a sexual partner than did females, but were nearly as selective as females when considering requirements for a long-term partner.

Two studies examined which traits males and females desire in partners at various levels of relationship development in an attempt to integrate evolutionary models (which emphasize sex differences) and social exchange models (which emphasize self-appraisals). In Study 1, male and female students specified their minimum criteria on 24 traits for a date, sexual partner, exclusive dating partner, marriage partner, and 1-night sexual liaison. They also rated themselves on the same dimensions. Sex differences were greatest for casual sexual liaisons, with men's criteria being consistently lower than women's. Men's self-ratings were generally less correlated with their criteria for a 1 -night stand, as well. Study 2 replicated the findings of Study 1, adding several modifications, including a measure of Ss' sex typing. Sex typing had few effects. The advantages of combining social psychological and evolutionary perspectives are discussed.

Four experiments examined the relation between behavioral expressions of dominance and the heterosexual attractiveness of males and females. Predictions concerning the relation between dominance and heterosexual attraction were derived from a consideration of sex role norms and from the comparative biological literature. All four experiments indicated an interaction between dominance and sex of target. Dominance behavior increased the attractiveness of males, but had no effect on the attractiveness of females. The third study indicated that the effect did not depend on the sex of the rater or on the sex of those with whom the dominant target interacted. The fourth study showed that the effect was specific to dominance as an independent variable and did not occur for related constructs (aggressive or domineering). This study also found that manipulated dominance enhanced only a male's sexual attractiveness and not his general Usability. The results were discussed in terms of potential biological and cultural causal mechanisms.

Three studies were conducted to explore the effect of path structure on the perception of traversed distance. Based upon anecdotal reports, it was hypothesized that the estimated length of a route would be positively related to the perceived number of turns on that route. Obtained data strongly supported this angularity hypothesis; increasing the number of right angle turns distributed along a pathway consistently increased the estimated length of the pathway. Controls used in these studies indicated that this effect was not due to actual or perceived travel time, to any particular path structure, or to the straight line distance between origin and goal. Three explanations of this finding were discussed: a storage size model, a scaling model, and an effort interpretation.

The present research investigates the hypothesis that cognitive representations of large scale space contain elements that may be termed reference points, and that these points are used to define the position of adjacent places. The nature and function of reference points is explored in five experiments. Experiments 1 and 2 consist of tasks during which subjects judged the distance between known locations. The subjective distance between reference points and nonreference points was found to be asymmetrical, with the latter ordered in relation to the former. Experiments 3 and 4 employ reaction time tasks in which subjects attempted to verify the distance or direction from an anchor location to target locations. The data indicate that the relative referentiality of anchor and target locations influences verification time. The results of Experiments 1-4 suggest that reference points occur in spatial cognition and that these points provide an organizational structure that facilitates the location of adjacent points in space. Experiment 5 consists of a multiple regression analysis designed to clarify the semantic attributes of spatial reference points.The authors would like to thank Clark Presson for his thoughtful critique of an earlier version of this article and Larry Gregory for his suggestions regarding data analysis.