How does the ecological foraging behavior of desert kangaroo rats (Dipodomys deserti) relate to their behavior on radial mazes?

Experiment 1 showed that laboratory-reared desert kangaroo rats, like domestic Norway rats, efficiently search for food on a radial arm maze (RAM) by avoiding revisiting arms within a trial. By placing an RAM on the floor so the animals could approach food from any direction, Experiment 2 tested whether efficient search by kangaroo rats was based on tactics of distance minimizing, central-place foraging, trail following, or meandering. In contrast to the dominant trail-following tactic of domestic Norway rats (Hoffman, Timberlake, Leffel, & Gont, 1999), kangaroo rats tended to distance minimize, whether maze arms were present or not. Experiment 3 indicated that kangaroo rats treated a floor configuration of eight food cups as two patches of four, based on beeline travel between patches and meandering within them. We conclude that similar performance in an elevated RAM by different species can be based on different tactics, and we suggest that a laboratory apparatus can be used to cast light on niche-related mechanisms.     

Mothers' ambivalence with their babies and toddlers: manifestations of conflicts with aggression

In this paper the author continues his study of conflicts over aggression in women, discussing the implications for contemporary theories of feminine psychology of observations of mothers in parent/child groups with their infants and toddlers. Many mothers experience conflicts over aggression (both in themselves and in their children) and become intolerant of their ambivalence toward their children. The author suggests that this observation provides an avenue that allows an integration of psychoanalytic ideas about maternity and childrearing with psychoanalytic understandings of women's conflicts about achievement in the social realm outside the home. In both roles, difficulties mastering conflicts with aggression may cause women to struggle profoundly, and to experience problems, in successfully negotiating their important life goals, whether the goals refer to their roles as effective mothers or their roles as effective individuals in the social sphere outside the home. Some women may demonstrate these difficulties in one sphere or the other, some in both, and others in neither. The author suggests on the one hand that we need to eliminate the concept of normality when considering the activities of women, and on the other hand that we need to normalize the omnipresence of ambivalence in the psychology of women.     

Parsing silhouettes: the short-cut rule.

Many researchers have proposed that, for the purpose of recognition, human vision parses shapes into component parts. Precisely how is not yet known. The minima rule for silhouettes (Hoffman & Richards, 1984) defines boundary points at which to parse but does not tell how to use these points to cut silhouettes and, therefore, does not tell what the parts are. In this paper, we propose the short-cut rule, which states that, other things being equal, human vision prefers to use the shortest possible cuts to parse silhouettes. We motivate this rule, and the well-known Petter's rule for modal completion, by the principle of transversality. We present five psychophysical experiments that test the short-cut rule, show that it successfully predicts part cuts that connect boundary points given by the minima rule, and show that it can also create new boundary points.     

Parsing silhouettes: The short-cut rule

Many researchers have proposed that, for the purpose of recognition, human vision parses shapes into component parts. Precisely how is not yet known. The minima rule for silhouettes (Hoffman & Richards, 1984) defines boundary points at which to parse but does not tell how to use these points to cut silhouettes and, therefore, does not tell what the parts are. In this paper, we propose the short-cut rule, which states that, other things being equal, human vision prefers to use the shortest possible cuts to parse silhouettes. We motivate this rule, and the well-known Petter’s rule for modal completion, by the principle of transversality. We present five psychophysical experiments that test the short-cut rule, show that it successfully predicts part cuts that connect boundary points given by the minima rule, and show that it can also create new boundary points.     

Early sexual experiences among pregnant and parenting adolescents.

One hundred sixty-six pregnant or parenting adolescent females completed a survey regarding early sexual experiences (wanted and unwanted), family dysfunction and violence, and health-risky behaviors occurring prior to age 18. Fifty-three percent had at least one unwanted sexual experience. Younger age at first unwanted sexual experience was associated with younger age at first wanted sexual experience. Adolescent females with an unwanted sexual experience, as compared to those without, were more likely to be victims of physical violence, to have run away, to be substance abusers, and to have family members with drug or alcohol problems. Four factors explained 39% of the variance in age at first pregnancy: presence of a family member with a drinking problem, age first got hit with a belt or other object by a family member, age first got drunk, and age at first wanted sexual experience. It was concluded that the prevention of teenage pregnancy entails a multifaceted approach that addresses family life, early sexual experiences, and health-risky behaviors.