Problem structure and the use of base-rate information from experience

This article is concerned with the use of base-rate information that is derived from experience in classifying examples of a category. The basic task involved simulated medical decision making in which participants learned to diagnose hypothetical diseases on the basis of symptom information. Alternative diseases differed in their relative frequency or base rates of occurrence. In five experiments initial learning was followed by a series of transfer tests designed to index the use of base-rate information. On these tests, patterns of symptoms were presented that suggested more than one disease and were therefore ambiguous. The alternative or candidate diseases on such tests could differ in their relative frequency of occurrence during learning. For example, a symptom might be presented that had appeared with both a relatively common and a relatively rare disease. If participants are using base-rate information appropriately (according to Bayes' theorem), then they should be more likely to predict that the common disease is present than that the rare disease is present on such ambiguous tests. Current classification models differ in their predictions concerning the use of base-rate information. For example, most prototype models imply an insensitivity to base-rate information, whereas many exemplar-based classification models predict appropriate use of base-rate information. The results reveal a consistent but complex pattern. Depending on the category structure and the nature of the ambiguous tests, participants use base-rate information appropriately, ignore base-rate information, or use base-rate information inappropriately (predict that the rare disease is more likely to be present). To our knowledge, no current categorization model predicts this pattern of results. To account for these results, a new model is described incorporating the ideas of property or symptom competition and context-sensitive retrieval.     

Role of the area postrema in three putative measures of motion sickness in the rat

After thermal cauterization of the area postrema in rats the absence of conditioned taste aversion to sucrose paired with lithium chloride (0.15 M, 3.3 ml/kg) was used as a pharmacologic/behavioral index of area postrema damage. In a subsequent experiment the effects of area postrema lesions on three measures proposed as species-relevant measures of motion sickness were studied, using off-vertical rotation at 150 degrees/s for either 30 or 90 min. Lesions of area postrema did not alter postrotational suppression of drinking or amount of defecation during motion. The initial acquisition of conditioned taste aversion to a novel cider vinegar solution paired with motion was not affected by lesioning of the area postrema, but these taste aversions extinguished more slowly in lesioned rats than in sham-operates or intact controls. Results are discussed in terms of proposed humoral factors which may induce motion sickness and in light of recent data on the role of the area postrema in similar measures in species possessing the complete emetic reflex.     

Understanding the central processing limit in consistent-mapping visual search tasks

Effects of load (i.e., the number of stimuli in the display) have been observed in multiple-frame studies using a consistent mapping of stimuli to responses (e.g., Fisher, 1982, 1984). In a series of four experiments, it is shown that these effects are not the consequence of differences across the high- and low-load conditions in either decision noise or peripheral masking. Additionally, it is shown that of two modes of limited capacity (a limited-channel and divided-capacity model) considered as possible explanations of load effects in tasks where subjects are required to locate a target, only one--the limited-channel model--is consistent with the results from all three location tasks. Finally, it is argued that the limited-channel model predicts not only the behavior observed in the four consistent-mapping experiments reported in this article but also the behavior observed in several related consistent-mapping tasks (Kleiss & Lane, 1986; Shiffrin & Gardner, 1972).     

The Values of Counseling: Three Domains

This article examines how values, as orienting beliefs about what is good for a client, group of clients, or a nation, affect the delivery of counseling services. Specifically, this article explores the role of value assumptions within such areas as counselor-client interactions, psychometrics, career services, and the transportability of counseling theories across national boundaries.     

Does spreading activation summate?

Summary Network models of semantic memory assume implicitly or explicitly that the degree of activation of a node is a monotonic function of the total amount of excitation reaching that node from all sources. For example, the activation level of the node representing apple should be greater if it is receiving excitation due to the activation of the nodes for fruit and pear than if only one of these neighboring nodes is activated. This notion was tested by presenting semantic primes 80 ms or 320 ms before a letter string (e.g., apple or ipple) requiring a lexical decision. The prime stimuli consisted of a pair of simultaneous items that were identical in the single prime condition (e.g., fruit/fruit or pear/pear) or different in the double prime condition (e.g., fruit/pear or pear/fruit), and were either related (target = apple) or unrelated (target = copper) to the target, or neutral. As predicted by the summation of semantic activation assumption of network models there was a larger priming effect (in the 320 ms SOA condition) following the simultaneous activation of two related nodes than following the activation of only one node.This research was supported by grants to the first author from the Natural Sciences and Engineering Research Council of Canada.     

Correlates of negative attitudes toward homosexuals in heterosexual college students

Negative attitudes toward homosexuals were assessed in 103 heterosexual college students. On the average, 17% of the sample agreed or strongly agreed with each of 40 negative statements about homosexuals. Cronbach's alpha and a principal components analysis indicated that the attitude scale was unidimensional. Methodological improvements were made in the assessment of the correlates of negative attitudes toward homosexuals. Such attitudes were inversely related to age, academic performance, and the use of principled moral reasoning. They were positively related to traditional attitudes toward men, women, and the equality of men and women. Compared to females, males' attitudes toward homosexuals were more negative, and their attitudes toward men, women, and the equality of men and women were more traditional. However, the correlates of negative attitudes toward homosexuals were similar for males and for females. It was concluded that negative attitudes toward homosexuals are part of a larger belief system regarding conventional social order.     

Academic achievement and attributions among college students: Effects of gender and sex typing

Attribution questionnaires were completed by 137 students in an introductory economics course immediately preceding the first exam in their class and immediately after their exams were returned. Results indicate that males and females used attributions differently, although not as a function of perceived outcome. In contrast, sex-typing groups varied their attribution as a function of perceived outcome. Self-esteem is proposed as a possible mediating variable. It was concluded that sex typing in relation to perceived successful and unsuccessful performance is an important variable in attributional research.     

A developmental-genetic analysis of aggressive behavior in mice (Mus musculus): III. Behavioral mediation by heightened reactivity or immobility?

This research was designed to investigate development and behavioral mediation in lines of ICR mice that have been selectively bred for aggressive behavior. General behavioral reactivity and behavioral immobility have been implicated as potential mediators by prior analyses of preattack interactions. To evaluate the separate roles of these dispositions, the emergence of attacks in genetically selected lines was tracked for 11 years by three levels of analysis: over successive generations, over development, and over dyadic interactions. Convergent outcomes were observed in all three levels with respect to two findings: (a) Robust line differences were obtained in attack behaviors, and (b) strong associations were found between line differences in attacks and line differences in behavioral immobility. Conversely, all three levels of analysis indicated a weak and inconsistent association between line differences in attacks and measures of social and nonsocial reactivity.     

Computerized Career Information and Guidance Systems: Caveat Emptor

Computerized career information and guidance systems, although now commonplace, have received little psychometric scrutiny. The authors argue for examining these systems in the same way in which paper and pencil instruments are assessed. Consideration is also given to issues related to programming, technical-service problems, and staffing.     

Marx,technocracy, and the corporatist ethos

Communism, in Marx' mind, did not mean simple liberation, but the economics of liberation. The realm of necessity (technē) was to become the primary field for emancipation (praxis), the latter taking form in new institutions, responsive to real socio-economic needs. In this sense, the problem of technocracy and the corporatist ethos in Marx are part of a broader discursive structure, which links the experiences of workers through the industrial revolution with the philosophies ofpraxis as they reach from Hegel through Marković.