The discrimination of heading from optic flow is not retinally invariant

Three experiments were conducted to determine whether the discrimination of heading from optic flow is retinally invariant and to determine the importance of acuity in accounting for heading eccentricity effects. In the first experiment, observers were presented with radial flow fields simulating forward translation through a three-dimensional volume of dots. The flow fields subtended 10° of visual angle and were presented at 0°, 10°, 20°, and 40° of retinal eccentricity. The observers were asked to indicate whether the simulated movement was to the right or the left of a target that appeared at the end of the display sequence. Eye movements were monitored with an electrooculogram apparatus. In a second experiment, static acuity thresholds were derived for each of the observers at the same retinal eccentricities. There was a significant increase in heading detection thresholds with retinal eccentricity (from 0.92° at 0° retinal eccentricity to 3.47° at 40°). An analysis of covariance indicated that the variation in sensitivity to radial flow, as a function of retinal eccentricity, is independent of acuity. Similar results were obtained when the Vernier acuity of observers was measured. These results suggest that the discrimination of heading from radial flow is not retinally invariant.     

Discovery algorithms for hierarchical relations

Two algorithms based on a latent class model are presented for discovering hierarchical relations that exist among a set ofK dichotomous items. The two algorithms, stepwise forward selection and backward elimination, incorporate statistical criteria for selecting (or deleting) 0–1 response pattern vectors to form the subset of the total possible 2 ^k vectors that uniquely describe the hierarchy. The performances of the algorithms are compared, using computer-constructed data, with those of three competing deterministic approaches based on ordering theory and the calculation of Phi/Phi-max coefficients. The discovery algorithms are also demonstrated on real data sets investigated in the literature.     

Validation française d'un inventaire de micro-stresseurs de la vie quotidienne: combinaison du “Daily Hassles Scale” et du “Uplifts Scale”

Ce travail présente les résultats d'une étude de validité de la version française d'un instrument d'auto-évaluation des micro-stresseurs de la vie quotidienne (“Daily Hassles Scale”; “Uplifts Scale”; Lazarus & Folkman, 1989). Les informations de validité reposent sur des structures factorielles ainsi que des analyses de cohérence interne et de convergence avec une mesure de stress psychologique (MSP: Lemyre, Tessier, & Fillion, 1990). Auprès d'une communauté universitaire (N = 265), six facteurs d'embětements quotidiens et cinq facteurs d'encouragements journaliers ont été isolés. Comme prévu, le score d'intensité aux différents facteurs d'embětements corrèle positivement et significativement avec l'état d'ětre stressé ce qui n'est pas le cas des encouragements quotidiens. La discussion soulève la nécessité d'utiliser différents groupes de micro-stresseurs plutôt qu'un facteur général. Elle évalue également le rôle ambigu des encouragements quotidiens comme facteur de protection dans l'expérience du stress.     

Neurons in Human Temporal Cortex Active with Verbal Associative Learning

In neuronal activity recorded from human middle temporal gyrus during learning of associations between word pairs, a population was identified that had greater activity for associations that were learned rapidly during initial encoding compared to those learned slowly or not at all by an individual subject. This population can be separated from other neurons by the combination of inhibition during word reading when no learning is required and excitation during recent memory for words. These neurons are present in both hemispheres, predominately in deeper layers of cortex. During initial encoding, the increased activity appears at presentation of all word pairs but persists for several seconds only for the rapidly learned pairs, likely reflecting rehersal of items being learned. Human associative learning is related to activity of this specific population of “association” neurons, identified here for the first time.     

GENDER-RELATED PATTERNS OF HELPING AMONG FRIENDS

In this study, the social role theory of gender and helping (Eagly & Crowley, 1986) was applied to understand gender differences in helping behavior. Relationships among criterion variables of time spent helping and help quality; and key predictors of problem severity, empathic tendency, anger, sympathy, closeness, causal controllability, coping, and self-efficacy were applied. Participants from a large community sample ( N = 1,004) described situations in which they helped a friend and completed questionnaires describing factors that influenced their actions. Recipients of the help also filled out similar questionnaires. It was found that across many problem settings women spend more time helping, give higher quality help, and feel more empathy and sympathy in response to their friends' problems. Further, the presence of anger toward a friend is associated with more time spent helping but a lower quality of help. In contrast, men rate their friends' problems as more controllable/blameworthy and experience more anger. Further, controllability has a greater influence on a number of help-related variables. For both men and women, self-efficacy and perception of problem severity are the greatest direct predictors of helping.     

The Theology of the Cross and God's Work in the World

Ian Barbour has distinguished eight theologies of God's role in nature, together with corresponding models of divine activity. This essay examines these ideas in the light of a theology of the cross. Three of Barbour's approaches—the neo-Thomist, the kenotic, and the existentialist—are able to provide different aspects of a theology of divine action that is consistent with belief that God's definitive revelation takes place in the Crucifixion and Resurrection of Jesus of Nazareth. These approaches encourage attention to a part of traditional doctrines of Providence, the idea that God acts by "cooperation" with natural processes. The kenotic character of divine involvement in the world means that the regularities of the basic interactions of physics are maintained. The idea of cooperation can be extrapolated into the past, to give some insight into ways of understanding God's activity in originating the universe.