The development of category learning strategies: What makes the difference?

Category learning can be achieved by identifying common features among category members, distinctive features among non-members, or both. These processes are psychologically and computationally distinct, and may have implications for the acquisition of categories at different hierarchical levels. The present study examines an account of children’s difficulty in acquiring categories at the subordinate level grounded on these distinct comparison processes. Adults and children performed category learning tasks in which they were exposed either to pairs of objects from the same novel category or pairs of objects from different categories. The objects were designed so that for each category learning task, two features determined category membership whereas two other features were task irrelevant. In the learning stage participants compared pairs of objects noted to be either from the same category or from different categories. Object pairs were chosen so that the objective amount of information provided to the participants was identical in the two learning conditions. We found that when presented only with object pairs noted to be from the same category, young children (6 ? YO ? 9.5) learned the novel categories just as well as older children (10 ? YO ? 14) and adults. However, when presented only with object pairs known to be from different categories, unlike older children and adults, young children failed to learn the novel categories. We discuss cognitive and computational factors that may give rise to this comparison bias, as well as its expected outcomes.     

Logical Theories of Intention and the Database Perspective

While logical theories of information attitudes, such as knowledge, certainty and belief, have flourished in the past two decades, formalization of other facets of rational behavior have lagged behind significantly. One intriguing line of research concerns the concept of intention. I will discuss one approach to tackling the notion within a logical framework, based on a database perspective.     

The effects of naloxone administered into the periaqueductal gray on shock-elicited freezing behavior in the rat

Freezing behavior that occurs following footshock was found to increase in rats in which naloxone was injected into the ventrolateral region of the mesencephalic periaqueductal gray (PAG) area of the brain prior to footshock administration. Since naloxone administered into the ventrolateral region of the PAG induced minimal freezing in rats which did not receive footshock, the results suggest that the effect of naloxone on shock-induced freezing is not due to a nonspecific decrease in motor activity. Naloxone had no effect on freezing when injected into the dorsolateral region of the PAG. The data are consistent with the theory that conditioned fear induces opioid mediated analgesia, and that the ventrolateral region of the PAG is an important component of a pain-inhibitory system involved in this analgesia.     

When Two Heads Aren't Better Than One: AIDS Risk Behavior in College-Age Couples1

Individuals in intimate relationships engage in higher levels of HIV risk behavior than do individuals engaging in casual sex (e.g., Bowen & Michal-Johnson, 1989; Misovich, Fisher, & Fisher, 1996). While there are many possible reasons for this consistent pattern of effects, few studies have focused on identifying the underlying causes. Therefore, same-gender focus groups were conducted with college-age men and women in intimate relationships as participants in order to examine, qualitatively, factors particular to relationships which are associated with HIV risk. Focus-group members indicated that concerns about questioning interpersonal trust and commitment in their relationship through the introduction of condoms or HIV testing were often strong impediments to these practices. Recommendations for future HIV-prevention interventions specific to individuals in relationships are discussed.     

Symmetry as a method of proof

This paper is a logical study of valid uses of symmetry in deductive reasoning, of what underlying principles make some appeals to symmetry legitimate but others illegitimate. The issue is first motivated informally. A framework is then given covering a fairly broad range of symmetry arguments, and the formulation of symmetry provided is shown to be a valid principle of reasoning, as is a slightly stronger principle of reasoning, one that is shown to be in some sense as strong as possible. The relationship between symmetry and isomorphism is discussed, and finally the framework is extended to a more general model-theoretic setting.     

The psychology of moderate prediction : I. Experience with multiple determination

In the experiments reported here, individuals with experience in a multivariate prediction setting showed considerable moderation of subsequent univariate predictions, compared to those without such experience. We show that such moderation of prediction does not result from an abstract rule of regression to the mean; rather, it can be explained by the named error model. According to this model, missing predictors are treated as an error term, with their unknown values replaced by central tendencies. Experiment 1 demonstrates the phenomenon of moderation following multivariate experience and explores its generalization to novel predictors. Moderation occurs even for a perfectly valid predictor, contrary to normative application of a regression strategy. Experiment 2 shows that the phenomenon depends on lack of correlation among the multivariate predictors. This accords with the named error model, which asserts that if missing predictors are perceived to be correlated with the available predictor, their unknown values are replaced by extreme values rather than by central tendencies. Experiment 3 shows that mere exposure to additional predictors has no effect; experience in which multiple predictors are used to make numerical predictions seems to be necessary in order to obtain subsequent moderation. In Experiment 4, feedback is introduced. Moderation of prediction results even without prior multivariate experience. However, multivariate experience produces the moderation effect much more quickly.     

TEACHER POPULARITY AND CONTRAST EFFECTS IN A CLASSROOM TOKEN ECONOMY

There is a common fear that the use of a token economy in one classroom might harm pupil performance in situations where the contingencies are not in effect. This study investigated potential contrast effects on measures of children's productivity and attitudes toward teachers. Six children with reading deficits participated. A multiple baseline design was used to assess the effects of a token economy which was systematically introduced across three teachers. Dependent measures included two rating forms of teacher popularity and work rate on a programmed reading series. The results indicated that the token system was effective in increasing the children's productivity and that no consistent behavioral contrast effects occurred. Furthermore, children's attitudes toward teachers did not appear to be influenced by the token economy until only one teacher was not delivering tokens. At this point, her popularity declined until she also delivered tokens. The token economy manipulation appeared to have a specific, desirable effect on the targeted behavior (i.e., work rate) and had minimal negative or positive “side effects” on teacher popularity.     

An experimental space combining individual and social performances

This report describes several primate environments in which two or more animals shared a common social area. Automatic programming was used to permit concurrent individual sessions. Some of the behavioral phenomena observed in these environments, including reinforcing properties of social interactions, are discussed.     

Event-based prospective memory for poorly attended events

In the most frequently used paradigm for studying event-based prospective memory (PM, Einstein & McDaniel, 1990), participants perform an ongoing task and are asked to perform an additional task when a particular stimulus (the PM cue) is presented. In this study three experiments examined how PM performance depends on stimulus selection, which is a major process involved in executive task control according to current theorizing. Participants made semantic judgments about a target word accompanied by two nontargets (distracters). The target was indicated by its spatial position (Experiment 1) or color (Experiment 2). The findings indicated that PM performance was much poorer when the PM cue was irrelevant to the ongoing task, in spite of the fact that nontargets were processed semantically as shown in Experiment 3.     

Methodological challenges in union commitment studies

Methodological problems in studies of union commitment were identified and illustrated with data from 4,641 members and 479 stewards in 297 local teachers' unions. Using a 20-item union commitment scale, results confirmed the existence of 3 substantive factors and 1 method factor at the individual level of analysis: loyalty to the union, responsibility to the union, willingness to work for the union, and a factor of negatively worded items. Tests of measurement invariance showed that the scale captured commitment for rank-and-file members but not for union stewards. The authors also found partial measurement invariance between long-time and newer members and full measurement invariance between men and women. Finally, the authors found that violation of the statistical assumption of independence reduced model fit when individual commitment scores were analyzed without attention to the hierarchical nature of the data.