Perceptual organization influences visual working memory

Previous studies have demonstrated that top-down factors can bias the storage of information in visual working memory. However, relatively little is known about the role that bottom-up stimulus characteristics play in visual working memory storage. In the present study, subjects performed a change detection task in which the to-be-remembered objects were organized in accordance with Gestalt grouping principles. When an attention-capturing cue was presented at the location of one object, other objects that were perceptually grouped with the cued object were more likely to be stored in working memory than were objects that were not grouped with the cued object. Thus, objects that are grouped together tend to be stored together, indicating that bottom-up perceptual organization influences the storage of information in visual working memory.     

Self-injurious behavior: gene-brain-behavior relationships

This paper summarizes a conference held at the National Institute of Child Health and Human Development on December 6-7, 1999, on self-injurious behavior [SIB] in developmental disabilities. Twenty-six of the top researchers in the U.S. from this field representing 13 different disciplines discussed environmental mechanisms, epidemiology, behavioral and pharmacological intervention strategies, neurochemical substrates, genetic syndromes in which SIB is a prominent behavioral phenotype, neurobiological and neurodevelopmental factors affecting SIB in humans as well as a variety of animal models of SIB. Findings over the last decade, especially new discoveries since 1995, were emphasized. SIB is a rapidly growing area of scientific interest to both basic and applied researchers. In many respects it is a model for the study of gene-brain-behavior relationships in developmental disabilities.     

Simulating consciousness in a bilateral neural network: "nuclear" and "fringe" awareness

A technique for the bilateral activation of neural nets that leads to a functional asymmetry of two simulated "cerebral hemispheres" is described. The simulation is designed to perform object recognition, while exhibiting characteristics typical of human consciousness-specifically, the unitary nature of conscious attention, together with a dual awareness corresponding to the "nucleus" and "fringe" described by William James (1890). Sensory neural nets self-organize on the basis of five sensory features. The system is then taught arbitrary symbolic labels for a small number of similar stimuli. Finally, the trained network is exposed to nonverbal stimuli for object recognition, leading to Gaussian activation of the "sensory" maps-with a peak at the location most closely related to the features of the external stimulus. "Verbal" maps are activated most strongly at the labeled location that lies closest to the peak on homologous sensory maps. On the verbal maps activation is characterized by both excitatory and inhibitory Gaussians (a Mexican hat), the parameters of which are determined by the relative locations of the verbal labels. Mutual homotopic inhibition across the "corpus callosum" then produces functional cerebral asymmetries, i.e., complementary activation of homologous "association" and "frontal" maps within a common focus of attention-a nucleus in the left hemisphere and a fringe in the right hemisphere. An object is recognized as corresponding to a known label when the total activation of both hemispheres (nucleus plus fringe) is strongest for that label. The functional dualities of the cerebral hemispheres are discussed in light of the nucleus/fringe asymmetry.     

Ontological issues in distance perception: cue use under full cue conditions cannot be inferred from use under controlled conditions

Phosphorescent square tiles (arranged to yield a single image size) were viewed in the dark by 56 monocular observers who utilized a chinrest. The targets were placed at one of three horizontal distances and at one of three eye heights, allowing us to study the relative effect of height in the visual field (HVF) and sagittal distance on observers' verbal reports of the horizontal distance at which the object lay (near, middle, or far). In Experiment 1, we found that reports covaried primarily with HVF and, as predicted, they exhibited a weak paradoxical inverse relation with horizontal distance. In a second and third experiment, a visible surface was placed under the targets at the three eye heights in both dark and fully lighted conditions. In this situation, the inverse distance relation disappeared, and HVF no longer influenced the judgments of most observers. The results show that information projected from relevant support surfaces is essential for veridical information about object distance. These results raise fundamental issues for perceptual researchers regarding how to decide when a cue has been properly delineated, given the assumption that the relation between a cue and what it specifies is probabilistic.     

PREFERRING HOUSEWIVES TO FEMINISTS

Four studies are described outlining the favorability of attitudes toward women. In Study 1, participants indicated their attitudes toward women and men and their construal of the term women. The results revealed that women were evaluated more favorably than men, but that male right-wing authoritarians (RWAs) who construed women as referring primarily to feminists were least favorable in their attitudes. In Study 2, participants indicated their attitudes toward both housewives and feminists. The results revealed that feminists were evaluated less favorably than housewives, and that the most negative attitudes toward feminists were expressed by authoritarian men. Study 3 revealed that high-RWA males held more negative symbolic beliefs concerning feminists (i.e., beliefs that feminists failed to promote participants'values) and that these beliefs accounted for variation in attitudes among high RWAs and much of the RWA-attitude relation. Finally, Study 4 revealed that high RWAs perceived greater value dissimilarity between them-selves and feminists. The implications of the findings for future research are discussed.     

Dentists' voice control: effects on children's disruptive and affective behavior

Voice control, a punishment technique based on loud commands, has been used widely in pediatric dentistry. This study examined whether (a) loudness is a necessary component of the technique, (b) voice control actually reduces children's disruptive behavior, and (c) after treatment, children's negative affect increases. Subjects were forty 3 1/2- to 7-year-olds who posed potential behavior problems and who were scheduled for cavity restoration. Children were assigned randomly to either loud- or normal-voice groups. Children who were assigned to either group but who were not disruptive formed a nonexperimental control group. Prior to and after treatment, children reported their feelings using the Self-Assessment Mannequin. Disruptive behavior was scored using the Behavior Profile Rating Scale. Results indicated that, following loud, but not normal voice commands, children reduced their disruptive behavior (p less than .004) and self-reported lower arousal (p less than .09) and greater pleasure (p less than .10). Theoretical and practical implications of these findings are discussed.     

Colour inputs to random-dot stereopsis.

Recently it has been claimed by Livingstone and Hubel that, of three anatomically and functionally distinct visual channels (the magnocellular, parvocellular interblob, and blob channels), only the magnocellular channel is involved in the processing of stereoscopic depth. Since the magnocellular system shows little overt colour opponency, the reported loss of the ability to resolve random-dot stereograms defined only by colour contrast seems consistent with this view. However, Julesz observed that reversed-contrast stereograms could be fused if correlated colour information was added. In the present study, 'noise' (non-corresponding) pixels were injected into random-dot stereograms in order to increase fusion time. All six subjects tested were able to achieve stereopsis in less than three minutes when there was only correspondence in colour and not in luminance, and three when luminance contrast was completely reversed. This ability depends on information about the direction of colour contrast, not just the presence of chromatic borders. When luminance and chromatic contrast are defined in terms of signal-to-noise ratios at the photoreceptor mosaic, chromatic information plays at least as important a role in stereopsis as does luminance information, suggesting that the magnocellular channel is not uniquely involved.