Field dependence as a limiting factor in solving a complex learning problem

Subjects in a prior study of complex learning often experienced difficulty in mastering the task because of an apparent reluctance to release one perceptual field and reconstrue the task on a higher cognitive level. It was hypothesized that were this the correct explanation, the faster learners would be more field independent on a measure of field dependence, since independence has been defined in terms of ease in releasing one's attention from the immediate perceptual field. This hypothesis was tested with 22 undergraduate subjects for whom Group Embedded Figures Test scores were correlated with the number of trials to completion on the complex learning task. A moderate but significant correlation supported the hypothesis.     

Representation and retention of three-event sequences in pigeons

The present experiments studied a three-event delayed sequence-discrimination (DSD) task: one arrangement (order) of two stimuli (red and yellow overhead lights) taken three in succession (e.g., red, yellow, red) was the positive sequence and the remaining seven arrangements were the negative sequences for responding and reward during the subsequent test stimulus. In Experiment 1, the final stimulus (recency) and the order of stimuli in the positive sequence controlled acquisition of discrimination. In Experiment 2, increasing the duration of memory intervals between stimuli reduced the discriminability of those negative sequences identical to the positive sequence after the delay. Three-event DSD performance in Experiments 1 and 2 was similar to two-event DSD performance in comparable published experiments. Models developed to explain pigeon performance in two-event DSD were extended to the three-event task. Results from both two- and three-event versions of the DSD task falsified a noncumulative model and several cumulative integration models (i.e., adding, averging, and some multiplying models), but corroborated one cumulative, multiplying model.     

Infant hypotonia, obesity, hypogenitalism and oligophrenia--new viewpoints on the etiology and symptoms of Prader-Willi syndrome

We present four cases of Prader-Willi syndrome. Two of them have an abnormality of a chromosome 15, the other both show different chromosomal abnormalities. Translocations or deletions were found recently in the bands 15q11/12 in about 60% of the cases of Prader-Willi syndrome. The consequences for diagnosis, symptomatology and genetic counselling of the syndrome are discussed.     

Social categorization,visual cues,and social judgements

Recent research on social cognition suggests that lifelike visual and vocal information about a person may strongly mediate the impact of prior social categorical knowledge on social judgements. Other research, however, on the contribution of visual cues to impression formation, suggests that they have relatively little impact. This study sought to resolve these conflicting findings by examining the effect of visual cues on social judgements when subjects possess prior social categorical knowledge varying in salience to the experimental task. Videotaped target interviews were monitored by observers in either sound and vision or sound only, and measures were taken of the targets' perceived personality, their ‘actual’ and ‘predicted’ social performance, and social acceptance by observers. Whilst salience of categorization strongly influenced the quality of judgements, visual cues had little if any effect. However, visual cues strongly influenced subjects' confidence in all three sets of judgements, sound and vision subjects being consistently more confident than their sound only counterparts. The findings are discussed in relation to previous research in both social cognition and visual cues.     

Suppression of corticosterone synthesis alters the behavior of hippocampally lesioned rats

The suppression of corticosterone synthesis with metyrapone (25 mg/kg) reduced the hyperactivity and altered the exploratory activity of hippocampally lesioned animals (HPC) in the open field to the level of cortical and sham controls (Experiment 1). In a second experiment, corticosterone (600 micrograms/kg) pretreatment 2 h, but not 1 h, before metyrapone partially restored the hyperactivity of HPC animals that had been decreased by the corticosteroid-suppressant drug. Alterations in exploratory behavior induced by metyrapone were also prevented by corticosterone pretreatment. The results suggest that the suppression of corticosterone in hippocampally lesioned animals produces a normalization of behavior that can be prevented by pretreatment with corticosterone.     

Effects of social isolation in adulthood on odor preferences and urine-marking in male rats

Male rats isolated for 60 days in adulthood spent less time investigating odors of females and urine-marked less over these odors than did males kept in groups of three. Isolated males did not differ from grouped males in their responses to odors of unfamiliar males or their own odors. After social experience the isolated males showed an increase in urine-marking but no change in odor preferences. Individual housing therefore appears to alter olfactory communication in the same way that it does other social behaviors and these changes may be mediated by the same mechanisms.