The computational connection in vision: Early orientation selection

It is widely accepted that computer implementations can play a role in verifying psychological theories. In this paper, I argue for a much broader and more abstract role for computation, in particular, one that includes formulation as well as verification. Consideration of issues of abstract computation—what should be computed and how-provides a level of analysis between ecological issues at the problem level and realization issues at the physiological level. This is the computational connection. The paper reflects my personal experience so that my argument can be made concretely. I concentrate on the evolution of one theory of orientation selection, and I show how we were led to differential geometry from “line detectors”; how parallel, distributed computational modeling led to novel proposals regarding curvature estimation; and how these proposals predicted psychophysical sensitivity to discontinuities.     

宗教信徒之视野

宗教作为一种社会意识形态,对社会存在的反映有其特殊的方式,这种反映方式使信徒与非信徒有所区别。本文以宗教信徒与非宗教信徒之共处的社会环境为背景,在逐次排除其反映社会生活的共同方面的基础上,从而引出两者对社会生活反映方式的根本差别,就在于信徒有着对社会生活的双重视野及价值标准,而这也正是信徒所特有的,并一直被宗教所传承的共性。     

On the nature of perceptual limits in vision

Summary Studies of attention have generally assumed that the principal limit to visual perception involves the capacity to identify a stimulus. Analyses of responses in visual tasks, however, suggest that errors can arise from a loss of position information, as well as a loss of identity information, and that these two types of errors may be affected by different variables. Based on this, we have proposed that the difficult aspect of perception is not that of recognizing the form of the stimulus but rather determining its position relative to other items in the field. To demonstrate this, we conducted a series of experiments on lateral masking that showed that the failure to perceive a parafoveal stimulus surrounded by other items is due to two quite separate components: a loss of identity information induced by the immediately adjacent items and a loss of position information induced by both adjacent and non-adjacent items.This research was supported by grant A-9581 from the Natural Sciences and Engineering Research Council of Canada to the senior author. The first two experiments were reported in a paper to the annual meeting of the Psychonomics Society, San Antonio, 1984     

Investigating spatial vision and dynamic attentional selection using a gaze-contingent multiresolutional display

This study examined spatial vision and attentional selection using a gaze-contingent multiresolutional display, with a dynamic, gaze-centered, high-resolution window and lower resolution periphery. Visual search times and eye movements from 15 participants in a 3 x 3 design (Window Radius x Peripheral Resolution) suggest that contrast sensitivity as a function of retinal eccentricity affects attentional selection and visual processing. Smaller windows led to longer search times and shorter saccades; lower peripheral resolution also shortened saccades (all ps < .05) as a result of avoiding fixating degraded areas. Fixation durations, although longer for smaller windows (p < .05), were unaffected by whether the next saccade went within or outside the window. These results are explained through (a) competition among potential saccade targets where above-threshold filtering reduces an object's relative salience and (b) generally disrupted visual processing.     

On the plausibility of Superman's x-ray vision

Requirements that a vision system must meet to make Superman 's x-ray vision possible are stated, and two solutions are proposed. In one, emitted x-rays carry the information to Superman 's eyes; in the other, emitted rays make objects transparent to a second type of ray. Further subjects lending themselves to this type of research are superhearing , the biomechanics of leaping tall buildings, or being faster than a bullet.     

On the usefulness of 'what' and 'where' pathways in vision

The primate visual brain is classically portrayed as a large number of separate 'maps', each dedicated to the processing of specific visual cues, such as colour, motion or faces and their many features. In order to understand this fractionated architecture, the concept of cortical 'pathways' or 'streams' was introduced. In the currently prevailing view, the different maps are organised hierarchically into two major pathways, one involved in recognition and memory (the ventral stream or 'what' pathway) and the other in the programming of action (the dorsal stream or 'where' pathway). In this review, we question this heuristically influential but potentially misleading linear hierarchical pathway model and argue instead for a 'patchwork' or network model.     

On the selection of signals

In a previous paper, it was argued that alertness, selectivity (set), and processing capacity (consciousness) could be identified and studied as separate components of attention. The current paper develops this theme by showing that alertness does not affect the buildup of information within the memory system but only the rate at which a later system responds to that information. Thus, in standard reaction-time tasks, increased alertness produces a reduction in reaction ’time but no decrease in errors. In contrast, providing a model of the signal the S is to process improved both speed and accuracy. The,. presence of a model of what the S is to process varies the vertex neural response to that specific signal as compared to a mismatching signal in the first 200–300 msec after its presentation. Three accounts of this effect are: speeded processing of a matching stimulus, habituation of the electrical response to a matching stimulus, and prolonged or enhanced processing of a mismatch. Evidence favors the first of these explanations, but the other two cannot be dismissed as possible contributors to this effect.     

On the temporal dynamics of language-mediated vision and vision-mediated language

Recent converging evidence suggests that language and vision interact immediately in non-trivial ways, although the exact nature of this interaction is still unclear. Not only does linguistic information influence visual perception in real-time, but visual information also influences language comprehension in real-time. For example, in visual search tasks, incremental spoken delivery of the target features (e.g., “Is there a red vertical?”) can increase the efficiency of conjunction search because only one feature is heard at a time. Moreover, in spoken word recognition tasks, the visual presence of an object whose name is similar to the word being spoken (e.g., a candle present when instructed to “pick up the candy”) can alter the process of comprehension. Dense sampling methods, such as eye-tracking and reach-tracking, richly illustrate the nature of this interaction, providing a semi-continuous measure of the temporal dynamics of individual behavioral responses. We review a variety of studies that demonstrate how these methods are particularly promising in further elucidating the dynamic competition that takes place between underlying linguistic and visual representations in multimodal contexts, and we conclude with a discussion of the consequences that these findings have for theories of embodied cognition.     

On the geometric approach to multivariate selection

Multivariate selection can be represented as a linear transformation in a geometric framework. This approach has led to considerable simplification in the study of the effects of selection on factor analysis. In this note this approach is extended to describe the effects of selection on regression analysis and to adjust for the effects of selection using the inverse of the linear transformation.     

On the spatial extent of attention in object-based visual selection

A new test was devised to avoid previous confounds in measures of object-based limits on divided visual attention. The distinction between objects was manipulated across a wide spatial extent. Target elements appeared on the same object only when far apart, and appeared close only when on different objects, so that object effects could not be reduced to spatial effects, nor vice versa. Subjects judged whether two odd elements within a display of two dashed lines were the same or different. They performed better when the target elements were far apart on a common line rather than on two distinct lines, even though the latter arrangement was more likely. Thus, nonstrategic object-based limits on divided attention can arise even across large distances. However, when subjects were precued to expect targets in a narrow region of the display, the object effect was eliminated, implying that object-based selection may only operate within spatially attended regions.     

Elemental operations in vision

Many cognitive tasks are serial in that they require several steps that have to be carried out in a sequence. Here, I outline a new theory of how these processing steps are implemented in vision by networks of neurons that span several areas of the cerebral cortex. The theory explains how individual neurons can contribute to the elementary processing steps, and also how several processing steps can be arranged in a sequence to form more complex visual routines, just as computer programs can be composed of sequences of instructions. Evidence in support of the theory comes from recent neurophysiological findings in monkeys engaged in complex visual tasks. It is likely that future work will allow these ideas to be generalized to other sensory modalities and cognitive functions.     

Spatial attention in vision

Summary Human observers can selectively allocate processing resources to different areas of the visual field within a single fixation. This spatial attention system may affect either the quality of information extraction or the decisions and responses based on this information. This paper reviews evidence from behavioral, single-unit, and event-related potential paradigms; the evidence suggests a relatively early locus of spatial attention.This research was supported by the U. S. Army Research Office under contract DAAG 29-83-K-0049. Portions of this paper were presented to the Conference on Attention and Action, Bielefeld, West Germany, in July 1985     

Postattentive vision

Much research has examined preattentive vision: visual representation prior to the arrival of attention. Most vision research concerns attended visual stimuli; very little research has considered postattentive vision. What is the visual representation of a previously attended object once attention is deployed elsewhere? The authors argue that perceptual effects of attention vanish once attention is redeployed. Experiments 1-6 were visual search studies. In standard search, participants looked for a target item among distractor items. On each trial, a new search display was presented. These tasks were compared to repeated search tasks in which the search display was not changed. On successive trials, participants searched the same display for new targets. Results showed that if search was inefficient when participants searched a display the first time, it was inefficient when the same, unchanging display was searched the second, fifth, or 350th time. Experiments 7 and 8 made a similar point with a curve tracing paradigm. The results have implications for an understanding of scene perception, change detection, and the relationship of vision to memory.