An apparatus for the automatic presentation of object discriminations to monkeys

Object discriminations have traditionally been presented to monkeys by hand in the Wisconsin General Test Apparatus. This method is time-consuming and prone to various kinds of experimenter error. It has proved possible to administer object discriminations automatically by using a modification of the Gloster Saro VM 51 vending machine. This machine, which has space for up to 371 objects, moves them on trays by two electric motors, and the control circuits of these are adapted for external operation by relays and modular programming equipment. A series of simple object discriminations or a concurrent (serial) discrimination task can then be given by remote control. The objects are so treated that by touching either of them the animal completes a circuit, enabling the response to be recorded and appropriately reinforced. Learning in the apparatus seems to be about as efficient as in the Wisconsin General Test Apparatus.     

Perceptual selectivity for color and form

Three visual-search experiments tested whether the preattentive parallel stage can-selectively guide the attentive stage to a particular known-to-be-relevant target feature. Subjects searched multielement displays for a salient green circle that had a unique form when surrounded by green nontarget squares or had a unique color when surrounded by red nontarget circles. In the distractor conditions, a salient item in the other dimension was present as well. As an extension of earlier findings (Theeuwes, 1991), the results showed that complete top-down selectivity toward a particular feature was not possible, not even after extended and consistent practice. The results reveal that selectivity depends on the relative discriminability of the stimulus dimensions: the presence of an irrelevant item with a unique color interferes with parallel search for a unique form, and vice versa.     

Perceptual selectivity for color and form.

Three visual-search experiments tested whether the preattentive parallel stage can selectively guide the attentive stage to a particular known-to-be-relevant target feature. Subjects searched multielement displays for a salient green circle that had a unique form when surrounded by green nontarget squares or had a unique color when surrounded by red nontarget circles. In the distractor conditions, a salient item in the other dimension was present as well. As an extension of earlier findings (Theeuwes, 1991), the results showed that complete top-down selectivity toward a particular feature was not possible, not even after extended and consistent practice. The results reveal that selectivity depends on the relative discriminability of the stimulus dimensions: the presence of an irrelevant item with a unique color interferes with parallel search for a unique form, and vice versa.     

Adolescents' visual preference for color over form

This study is concerned with the visual preference for color over form among the Yoruba adolescents of Nigeria. The hypothesis is that Yoruba adolescent boys are more likely to demonstrate superior performance in a task involving cultural differences in visual selective attention preference for color over form than girls. One hundred 16-year-old adolescent boys and girls were randomly drawn from two secondary schools for this study. The instrument used was the Visual Selective Attention Color-Form Matching Experiment. Computation was carried out with a chi-square 2 X 2 contingency analysis. Results indicated that the hypothesis reached a .001 statistical level of significance. The theoretical implications of the findings are discussed.     

Explanation for neon color effect of chromatic configurations on the basis of perceptual ambiguity in form and color

Under reflected light conditions, we observed a neon color effect in a van Tuijl-type pattern for 30 combinations by pairing CMY inks. The results cannot be fully explained by Bressan's proposal as follows: (1) the illusory colors for the six configurations contradicted her predictions, (2) strong effects were not presented for complementary color pairs, and (3) for four configurations, the colors of line segments assimilated into those of the inducing patterns. Thus, the author proposes an hypothesis that the visual system treats neon color displays as ambiguous figures in form and color. This proposal can explain both illusory colors of the illusory area and those of the line segments themselves.     

Focal and nonfocal processing of color and form

Langley Porter Neuropychtatrte Institute, University of California, San Francisco. Californta 94122 Response latencies to color are usually shorter than those to form. but sometimes this difference is absent or reversed. Three experiments investigated whether these differences result from differential susceptibility of color and form to extra focal processing. Experiment I showed shorter same-difference latencies to color than to form when two stimuli were presented simultaneously. This difference disappeared or reversed when the two stimuh appeared sequentially. Experiment II. using a multistimulus matching task, found that differences between response latencies to form and color were minimal at the center of the display and increased peripherally. Experiment III showed that eye movements were more frequent in matching forms than colors. Tasks that produced many eye movements had long average latencies, but the relationship between eye movements and latency was not a simple one. There was evidence both for parallel and serial strategies tn the use of the eyes to gather information. The results of these experiments are considered in relation to a theory of distributed attention.     

An apparatus for the detection and counting of mouse squeals

An instrument, designed to detect and count mouse squeals and to reject other sounds which might confound the data, is described. A parts list is furnished.     

Detecting conjunctions of color and form in parallel

Researchers have proposed that graphical efficacy may be determined, in part, by the nature of the perceptual interactions that exist between attributes used to create graphical displays. One extreme type of interaction isintegrality, in which two or more physical dimensions are represented as a single psychological dimension in the observer. An alternative type of interaction isconfigurality, in which a global emergent dimension is availableto the observer in addition to the component attributes. Thirteen stimulus sets, each composed of attributes commonly used in the design of graphs, were submitted to the performance-based diagnostics of integrality and configurality. Analyses suggest a continuum of configurality among the present stimulus sets, with little evidence for integral graphical attributes. The configural pattern of results was more common when two identical dimensions were paired (homogeneous stimuli) than when two different dimensions were paired (heterogeneous stimuli). However, there was no evidence that pairs of dimensions belonging to a single object (object integration) were any more configural than dimensions belonging to different objects. Object integration was, however, consistently related to inefficient performance in tasks requiring the filtering of one of two component dimensions.     

Detecting conjunctions of color and form in parallel

Certain theories of visual attention assume that at least one processing stage must be serial when the target of search is defined as the conjunction of two or more separable features. To explain why conjunction-search response times do not always form linearly increasing functions of display size, recent versions of this general model have posited the existence of an early parallel process that guides the serial stage toward display elements that are likely targets. Other models have relaxed the seriality assumption, allowing for a limited number of parallel decisions. In the three experiments reported here, a redundant-target detection task was used with conjunctively defined targets and display sizes of two (Experiment 1), one or two (Experiment 2), and six (Experiment 3). In all three experiments, strong evidence for parallel processing was observed. The implications for models of elementary visual processes are discussed.     

An apparatus for recording figural after-effects

A simple apparatus is described by which Figural After-effects may be recorded directly from the subject's adjustments of a test figure. Curves which have been recorded confirm the results of other workers obtained by more laborious methods.