Base-rate effects in category learning: a comparison of parallel network and memory storage-retrieval models

Exemplar-memory and adaptive network models were compared in application to category learning data, with special attention to base rate effects on learning and transfer performance. Subjects classified symptom charts of hypothetical patients into disease categories, with informative feedback on learning trials and with the feedback either given or withheld on test trials that followed each fourth of the learning series. The network model proved notably accurate and uniformly superior to the exemplar model in accounting for the detailed course of learning; both the parallel, interactive aspect of the network model and its particular learning algorithm contribute to this superiority. During learning, subjects' performance reflected both category base rates and feature (symptom) probabilities in a nearly optimal manner, a result predicted by both models, though more accurately by the network model. However, under some test conditions, the data showed substantial base-rate neglect, in agreement with Gluck and Bower (1988b).     

Assessing the relationship of Type A beliefs to cardiovascular disease risk and psychosocial distress

Investigators have begun to take a multimodal approach to the assessment and treatment of psychosocial risk factors for cardiovascular disease (CVD). For instance, cognitive responses have become the focus of contemporary research along with continued examination of overt Type A behaviors. Price (1982) has outlined a set of beliefs purportedly associated with Type A behavior and subsequent CVD risk. The current study examines the validity of this belief set as represented by a newly developed measure, the Type A Cognitive Questionnaire (TACQ). Subjects were 221 employed adults participating in a worksite CVD risk reduction program. They completed the TACQ as part of a pretreatment CVD risk screening protocol. As hypothesized, TACQ scores were significantly associated with Type A behavior, hostility, physiological mediators of CVD, and psychosocial distress. Discussion addresses continued refinement of the Type A belief construct.     

Verbal and visuospatial recall by younger and older subjects: use of matched tasks

In this study, 18 older (over age 65, M = 75.61 years) and 18 younger (below age 40 and over age 17, M = 26.44 years) healthy volunteers were tested on verbal and visuospatial recall. Tasks were matched on discriminating power. Older Ss performed worse than younger Ss on both tasks. The older Ss also showed a larger deficit in visuospatial than in verbal recall, relative to the younger Ss. These results are consistent with the theory of aging according to which verbal tasks are more resistant to deterioration than are nonverbal tasks. A psychological explanation based on lifetime experience with verbal material is preferred over the physiological explanation advocating faster aging of the right hemisphere.     

Age differences in the acculturation process

Age differences were assessed in a conceptual model that seeks to explain how acculturation affects psychological well-being among Mexican Americans. The data were from a national probability sample of 859 persons of Mexican decent. It was hypothesized that low acculturation creates financial stress. Moreover, low acculturation and financial stress were in turn predicted to erode feelings of personal control and self-esteem. Finally, diminished feelings of control and low self-esteem were hypothesized to exert a negative impact on psychological well-being. When data from respondents of all ages was assessed, empirical support was found for all of the hypotheses except the linkage between acculturation and financial stress. However, few age differences emerged in the model. The authors conclude that older Mexican Americans may not be more vulnerable to the stressors associated with acculturation.     

Frontal lobe dysfunction and memory impairment in patients with chronic progressive multiple sclerosis

Deficits in semantic encoding have been described in patients with frontal lobe disease who also show memory impairments. As a group, patients with multiple sclerosis (MS) exhibit memory impairment, fail to make effective use of semantic encoding to aid memory, and perform poorly on verbal fluency and concept formation tests which are sensitive to frontal lobe damage. In the present study the semantic encoding capacity of MS patients was measured using a modification of Wicken's release from proactive interference (PI) paradigm. Individual patients varied considerably in the severity of their impairments on verbal fluency, verbal recognition memory and on Wisconsin Card Sorting Task, but even patients who evidenced both memory impairment and signs of frontal lobe dysfunction showed normal release from PI after a categorical shift. Memory disturbances in MS are unlikely to result from an incapacity for semantic encoding, which seems preserved in MS, but may arise instead from deficits in processing information rapidly.     

Sex differences in spontaneous alternation and open-field behavior of hamsters: Habituation differences

With a minimal intratrial interval, male golden hamsters spontaneously alternated significantly less often in a T-maze than females. Since there was no sex difference in choice latencies, the alternation difference could not be accounted for by longer intertrial intervals experienced by males. Instead, the difference was ascribed to faster rates of habituation to novelty in females because they showed greater between-sessions declines in open-field ambulation than males. From an analysis of rearing scores it was concluded that attempts to escape from the apparatus may have been the principal motivating influence in both the T-maze and open field.