A comparison of different measures of response strength in the study of stimulus generalization

In Experiment 1, three pigeons were given variable interval training to peck at a light of 550 mmu and then were tested for stimulus generalization in extinction to several different wavelengths. A gradient was obtained for latency of the first response in each test period, for the number of test periods in which responding occurred, and for the measure of response rate. When the response rate gradient was corrected for differences in initial latency and in number of responded trials, the change was minimal, indicating that the major component of response rate as usually measured is rate of responding having once responded. In Experiment 2, three other pigeons were trained to respond to 550 mmu (for variable interval reinforcement) and not to 570 mmu (extinguished). Analysis of generalization gradients dictated the same conclusion as that reported for generalization following single stimulus training.     

Male chacma baboons (Papio hamadryas ursinus) discriminate loud call contests between rivals of different relative ranks

Males in multi-male groups of chacma baboons (Papio hamadryas ursinus) in Botswana compete for positions in a linear dominance hierarchy. Previous research suggests that males treat different categories of rivals differently; competitive displays between males of similar rank are more frequent and intense than those between disparately ranked males. Here we test whether males also respond differently to male–male interactions in which they are not directly involved, using playbacks of the loud wahoo calls exchanged between competing males in aggressive displays. We played paired sequences of vocal contests between two adjacently ranked and two disparately ranked males to ten subjects, half ranking below the signalers in the call sequences and half above. Subjects who ranked above the two signalers showed stronger responses than lower-ranking subjects. Higher-ranking subjects also responded more strongly to sequences involving disparately ranked, as opposed to adjacently ranked opponents, suggesting that they recognized those individuals relative ranks. Strong responses to sequences between disparately ranked opponents might have occurred either because such contests typically involve resources of high fitness value (defense of meat, estrous females or infants vulnerable to infanticide) or because they indicate a sudden change in one contestants condition. In contrast, subjects who ranked lower than the signalers responded equally strongly to both types of sequences. These subjects may have been able to distinguish between the two categories of opponents but did not respond differently to them because they had little to lose or gain by a rank reversal between males that already ranked higher than they did.     

Visually guided step descent in children with Williams syndrome

Individuals with Williams syndrome (WS) have impairments in visuospatial tasks and in manual visuomotor control, consistent with parietal and cerebellar abnormalities. Here we examined whether individuals with WS also have difficulties in visually controlling whole-body movements. We investigated visual control of stepping down at a change of level in children with WS (5-16-year-olds), who descended a single step while their movement was kinematically recorded. On each trial step height was set unpredictably, so that visual information was necessary to perceive the step depth and position the legs appropriately before landing. Kinematic measures established that children with WS did not use visual information to slow the leg at an appropriate point during the step. This pattern contrasts with that observed in typically developing 3- and 4-year-old children, implying severe impairment in whole-body visuomotor control in WS. For children with WS, performance was not significantly predicted by low-level visual or balance problems, but improved significantly with verbal age. The results suggest some plasticity and development in WS whole-body control. These data clearly show that visuospatial and visuomotor deficits in WS extend to the locomotor domain. Taken together with evidence for parietal and cerebellar abnormalities in WS, these results also provide new evidence for the role of these circuits in the visual control of whole-body movement.     

Anterior cingulate cortex in schema assimilation and expression

In humans and in animals, mental schemas can store information within an associative framework that enables rapid and efficient assimilation of new information. Using a hippocampal-dependent paired-associate task, we now report that the anterior cingulate cortex is part of a neocortical network of schema storage with NMDA receptor-mediated transmission critical for information updating, and AMPA receptor-mediated transmission required for the expression and updating of stored information.     

Genetic Counseling Practices in Germany: A Comparison Between East German and West German Geneticists

As part of an international study of ethics and genetics, we present a comparison between survey responses of 43 East German and 212 West German geneticists to anonymous questionnaires. Both groups indicated that the experience of the Third Reich has impacted the genetics profession in Germany today. East German geneticists reported more directive counseling practices after prenatal diagnosis for 10 of 26 conditions than those from West Germany. When asked to give their personal opinions about pregnancy termination, East Germans were more accepting of abortion than their West German colleagues for 7 of 24 fetal indications. In addition, there were significant differences between the two sample groups for 8 questions on the perception of disability and society. Discussions with German geneticists suggest that, while both groups were affected by Germany's experience of Nazism, different abortion laws, political systems, and ideas about the doctor-patient relationship in former East and West Germany may account for discrepancies in reported genetic counseling practices and in attitudes toward abortion and disability.     

The child's fear of infanticide and the nuclear cause of the neuroses

The concept that the child is predisposed to the fear of infanticide, and that that fear may be the central cause of his psychological problems and the primary motive force of his defense, allows us to view the defensive process from a different perspective than that offered by Freud's nuclear theory. Children's fantasies make it apparent that the idealization of their parents' image, and the devaluation of their own, constitute their basic defense against their fear.