How many exemplars are used? Explorations with the Rex Leopold I model

The goal of this research is to test the hypothesis that a category is not necessarily represented by all observed exemplars, but by a reduced subset of these exemplars. To test this hypothesis, we made use of a study reported by Nosofsky, Clark, and Shin (1989), and replicated their Experiment 1 in order to gather individual-participant data. Both a full exemplar model and a reduced exemplar model were fit to the data. In general, the fits of the reduced exemplar model were superior to those of the full exemplar model. The results suggest that only a subset of exemplars may be sufficient for category representation.     

Psychosocial mediators of a lifestyle physical activity intervention in women

ObjectivesA lifestyle physical activity intervention in women based on the transtheoretical model and social–cognitive theory effectively increased physical activity. The aim of the present study was to examine possible mediators (perceived benefits and barriers of physical activity, self-efficacy, processes of change, and social support) of these physical activity changes.MethodsMembers of four units of a women's organization followed a six-month minimal-contact physical activity program. The intervention program included one group meeting, a self-help booklet and five monthly reminder letters. Members of two other units served as control group. Physical activity (accelerometer counts), and psychosocial constructs (self-report questionnaires) were assessed at baseline (pretest) and directly after the intervention (posttest). Women who completed all measurements (n = 101) were included in the mediation analyses.ResultsParticipants in the intervention group reported significantly greater increases in the use of behavioral processes from pretest to posttest than participants in the control group. None of the proposed psychosocial constructs showed a mediating effect on changes in physical activity.ConclusionsThe mechanisms proposed by the transtheoretical model and social–cognitive theory could not explain the positive effect of the intervention on physical activity. Identifying the working components of an intervention remains a challenging and necessary step in the development of effective low-cost and high-reach physical activity interventions.     

Semisupervised category learning: The impact of feedback in learning the information-integration task

In a standard supervised classification paradigm, stimuli are presented sequentially, participants make a classification, and feedback follows immediately. In this article, we use a semisupervised classification paradigm, in which feedback is given after a prespecified percentage of trials only. In Experiment 1, feedback was given in 100%, 0%, 25%, and 50% of the trials. Previous research reported by Ashby, Queller, and Berretty (1999) indicated that in an information-integration task, perfect accuracy was obtained supervised (100%) but not unsupervised (0%). Our results show that in both the 100% and 50% conditions, participants were able to achieve maximum accuracy. However, in the 0% and the 25% conditions, participants failed to learn. To discover the influence of the no-feedback trials on the learning process, the 50% condition was replicated in Experiment 2, substituting unrelated filler trials for the no-feedback trials. The results indicated that accuracy rates were similar, suggesting no impact of the no-feedback trials on the learning process. The possibility of ever learning in a 25% setting was also researched in Experiment 2. Using twice as many trials, the results showed that all but 2 participants succeeded, suggesting that only the total number of feedback trials is important. The impact of the semisupervised learning results for ALCOVE, COVIS, and SPEED models is discussed.     

Changes in repeated references: Collaboration or repetition effects?

According to the Clark & Wilkes-Gibbs' collaborative model of reference, the repetition of a referential communication task produces changes in the making of references (decreasing number of words and of turns with the passing trials, increasing number of definite references and of labels), and these changes are interpreted as revealing the outgrowth of a collaborative process aiming at mutual understanding at the lowest cost. Using a repeated referential paradigm but without any physically present interlocutor, the present study aimed at answering the question of whether these changes are attributable to the mere repetition of the referential task. In adifferent addressee (DA) condition, the subjects were told before each new trial that what they would say would be presented later to another person; in asame addressee 9SA) condition, the subjects were told before each new trial that what they would say would be presented to the same person. With the passing trials, the subjects in the DA condition produced more and more words, but did not use any definite references or labels: These observations have no common point with the ones obtained within a conversational framework. The data obtained from speakers in the SA condition were only slightly different and far from being close to the ones gained in referential dialogues: The number of words remains constant, there was only a slight increase of definite references, and there were no labels. Repetition itself clearly cannot account for the changes in referring that have been reported in recent studies of how subjects cooperate in the making of references.This research was partly supported by a project grant from the National Fund for Scientific Research (Belgium) to Y. Chantraine, research assistant at the University of Louvain in Belgium.     

Language in right-handers with right-hemisphere lesions: A preliminary study including anatomical, genetic, and social factors

A comprehensive test battery was devised to study the effects of right hemisphere lesions on the speech and language of “nonaphasic” dextrals. Data were thus obtained for 62 subjects, 20 of them neurologically healthy and 42 with a focal right hemisphere lesion resulting from a cerebro-vascular accident. A preliminary global analysis of these data is reported. Anomalies were observed in 33 brain-damaged subjects. Although discreet in all cases, these anomalies were shown to have various degrees of severity. Given the population submitted to this study, the subject most likely to show such anomalies was defined, genetically, as a right-handed adult with a family history of ambidextrality or left-handedness and, socially, as one with a relatively limited education. The implications of these findings are discussed together with the problem of the anatomo-clinical correlations of language disorders resulting from right hemisphere lesions in “nonaphasic” dextrals.     

Global Change: New Challenges for Psychology

Perception of environmental degradation and awareness of environmental hazards came gradually, and was followed by collective action. Global change is different because of its specific features, which raise new issues for action-oriented psychological research. The lack of consensus among scientists, the global nature of the change, and the type of risk are analysed in order to develop an agenda for research. Priority should be given to acquiring a better knowledge of the cognitive process in the face of serious danger with a high margin of uncertainty.     

Cerebral hemispheres and selective attention

The present paper is intended to discuss critically the integration model of the functional interhemispheric relation that has become dominant in neuropsychology with the development, in the last two decades, of split-brain studies.While the split-brain research has undoubtedly produced new experimental methodologies, the current theorizing in this area has been contrastingly conservative. The present paper examines some of its basic assumptions, in particular that the corpus callosum is an association pathway devoted to interhemispheric transmission of information, and that the disconnected cerebral hemispheres function in a parallel way. It is shown that these assumptions have only low consistency both with split-brain behavior and with the normal organization of the fore-brain connectivity.In the early seventies, theoretical novelty has emerged from another research field with Kinsbourne's interpretation of laterality effects in normal man. His concept of asymmetrical hemispheric arousal is shown to be supported, with some reservations, by evidence in this field. But this dynamical concept has a more general value and there are signs that current ideas about the functional relation between the cerebral hemispheres are presently deeply transformed.     

Sequences of phonemic approximations in aphasia

The trends of sequences of phonemic approximations to a single target were studied in three types of aphasia (Broca's, conduction, and Wernicke's), as gathered in five tasks (spontaneous speech, repetition of meaningful words, repetition of nonsense words, reading aloud, and automatized sequences). A phonemic error ratio was defined in order to quantify the distance between each approximation of a given sequence and its target. The results of a computer analysis based on this ratio were analyzed according to three parameters. A study of three types of patients revealed that conduction aphasics exhibited the most regular trend toward the target in sequences of phonemic approximations; the analysis of the various tasks indicated that sequences produced in repetition by conduction aphasics form an exception to the regularity of this trend, and an examination of the various lengths of sequences indicated that longer sequences showed a less decisive trend toward the target than shorter sequences. The discussion bears on some theoretical aspects of the phonological production mechanism and its control: the initial strength and permanence of the internal representation of the target emerge as important factors required for the good functioning of this mechanism.