双眼视差的神经机制与知觉学习效应

双眼瞳距使得空间某物体在左右眼视网膜的成像存在微小位置差异, 这种差异被称为双眼视差(binocular disparity), 是立体视知觉的重要信息来源。对双眼视差的心理物理学研究始于18世纪初, 迄今已有接近两百年的历史。近年来, 双眼视差研究主要集中在两方面。其一是用电生理、脑成像技术考察双眼视差在视觉背、腹侧通路的模块化表征, 其脑区表征反映出视觉系统的层级式、平行式加工规律。其二是应用知觉学习范式研究双眼视差的可塑性。未来研究应综合脑成像和神经调控技术考察双眼视差的神经机制及其学习效应, 包括双眼视差与多种深度线索间的信息整合和交互作用。应用方向上, 可结合虚拟现实等技术优化训练范式, 实现立体视力的康复和增强。     

On the possibility of "smart" perceptual mechanisms

Abstract.— A basic feature of some modem theories of perception is the notion of complex or higher order variables which are considered basic for perception. A distinction between "rote" and "smart" mechanisms is introduced and it is suggested that perception consists of smart mechanisms which directly register complex variables. A model of a perceiver, based on the smart polar planimeter, is constructed and used to illustrate the possible consequences of smart perceptual mechanisms for research in areas such as psychophysics, cognition, attention, and perceptual development and learning.     

Effects of stimulus synchrony on mechanisms of perceptual organization

When neurons adopt a synchronized, oscillatory response to stimulus Gestalten, the phase of those oscillations almost always varies relative to stimulus activity. This has been taken to indicate that form-coding mechanisms are synchronized by internal timing mechanisms, and/or may be sensitive to stimulus activity only via motion detectors. This proposal is problematic for interpreting recent demonstrations of the effects of stimulus synchrony particularly when stimuli are stationary. Here we offer an account of stimulus-driven synchronization supported by evidence that segmentation by stimulus synchrony can be relatively insensitive to explicit motion signals. The argument is made that qualitative similarities between the effects of phase-independent and phase-locked oscillations in the EEG, the effects of phase synchronization at the cellular level and evidence for phase-enhanced stimulus grouping should be considered as functionally equivalent. This argument emphasizes the flexibility of temporal synchrony as a code for perceptual organization.     

Iconic memory and its relation to perceptual processing and other memory mechanisms

Research on iconic memory is reviewed. Specific issues discussed include the duration of the icon, effects of stimulus variables, types of information lost, selection, processing capacity, and scanning. More general issues include the level of encoding in the icon and its relation to short-term memory. It is also argued that a number of experiments do not show what they were intended to show because of possible methodological problems. The view is developed that iconic memory is postretinal but uncoded; nor is it influenced directly by strategies or subsequent mechanisms.     

Multisensory perceptual learning reshapes both fast and slow mechanisms of crossmodal processing

Previous research has shown that sounds facilitate perception of visual patterns appearing immediately after the sound but impair perception of patterns appearing after some delay. Here we examined the spatial gradient of the fast crossmodal facilitation effect and the slow inhibition effect in order to test whether they reflect separate mechanisms. We found that crossmodal facilitation is only observed at visual field locations overlapping with the sound, whereas crossmodal inhibition affects the whole hemifield. Furthermore, we tested whether multisensory perceptual learning with misaligned audio-visual stimuli reshapes crossmodal facilitation and inhibition. We found that training shifts crossmodal facilitation towards the trained location without changing its range. By contrast, training narrows the range of inhibition without shifting its position. Our results suggest that crossmodal facilitation and inhibition reflect separate mechanisms that can both be reshaped by multisensory experience even in adult humans. Multisensory links seem to be more plastic than previously thought.     

Eye-tracking the own-race bias in face recognition: Revealing the perceptual and socio-cognitive mechanisms

Own-race faces are recognised more accurately than other-race faces and may even be viewed differently as measured by an eye-tracker (Goldinger, Papesh, & He, 2009). Alternatively, observer race might direct eye-movements (Blais, Jack, Scheepers, Fiset, & Caldara, 2008). Observer differences in eye-movements are likely to be based on experience of the physiognomic characteristics that are differentially discriminating for Black and White faces. Two experiments are reported that employed standard old/new recognition paradigms in which Black and White observers viewed Black and White faces with their eye-movements recorded. Experiment 1 showed that there were observer race differences in terms of the features scanned but observers employed the same strategy across different types of faces. Experiment 2 demonstrated that other-race faces could be recognised more accurately if participants had their first fixation directed to more diagnostic features using fixation crosses. These results are entirely consistent with those presented by Blais et al. (2008) and with the perceptual interpretation that the own-race bias is due to inappropriate attention allocated to the facial features ( and ).     

Shedding some light on catching in the dark: perceptual mechanisms for catching fly balls

To catch a lofted ball, a catcher must pick up information that guides locomotion to where the ball will land. The acceleration of tangent of the elevation angle of the ball (AT) has received empirical support as a possible source of this information. Little, however, has been said about how the information is detected. Do catchers fixate on a stationary point, or do they track the ball with their gaze? Experiment 1 revealed that catchers use eye and head movements to track the ball. This means that if AT is picked up retinally, it must be done by means of background motion. Alternatively, AT could be picked up by extraretinal mechanisms, such as the vestibular and proprioceptive systems. In Experiment 2, catchers reliably ran to intercept luminous fly balls in the dark, that is, in absence of a visual background, under both binocular and monocular viewing conditions. This indicates that the optical information is not detected by a retinal mechanism alone.     

Attention and perceptual priming in the perceptual identification task

Prior research indicates that manipulations of attention during encoding sometimes affect perceptual implicit memory. Two hypotheses were investigated. One proposes that manipulations of attention affect perceptual priming only to the extent that they disrupt stimulus identification. The other attributes reduced priming to the disruptive effects of distractor selection. The role of attention was investigated with a variant of the Stroop task in which participants either read words, identified their color, or did both. Identifying the color reduced priming even when the word was also overtly identified. This result held regardless of whether color and word were presented as a single object (Experiments 1 and 2) or as separate objects (Experiment 4). When participants read and identified a color, the overt order of the responses did not matter; both conditions reduced priming relative to reading alone (Experiment 3). The results provide evidence against the stimulus-identification account but are consistent with the distractor-selection hypothesis.     

Effects of preexposure on stimulus discrimination: An investigation of the mechanisms responsible for human perceptual learning

The effect of preexposure on human perceptual learning was investigated in four experiments. In Experiments 1a and 1b, participants were preexposed to one pair of visual stimuli on an intermixed schedule (AX/BX) and one on a blocked schedule (CX_DX). The ability to discriminate between AX and BX and between CX and DX was then assessed by examining the extent to which key presses assigned to each member of a stimulus pair generalized to the other member (Experiment 1a) and by looking at the accuracy of same–different responses (Experiment 1b). Stimuli were more easily discriminated following intermixed than following blocked preexposure on both the generalization and same–different tasks. This suggests that two stimuli are more perceptually distinct after intermixed preexposure. Experiments 2a and 2b investigated the mechanisms responsible for perceptual learning using same–different tasks. The results support the suggestion that the enhanced discrimination observed after intermixed preexposure is due to increases in the salience of the unique elements.     

Effects of preexposure on stimulus discrimination: an investigation of the mechanisms responsible for human perceptual learning

The effect of preexposure on human perceptual learning was investigated in four experiments. In Experiments 1a and 1b, participants were preexposed to one pair of visual stimuli on an intermixed schedule (AX/BX) and one on a blocked schedule (CX_DX). The ability to discriminate between AX and BX and between CX and DX was then assessed by examining the extent to which key presses assigned to each member of a stimulus pair generalized to the other member (Experiment 1a) and by looking at the accuracy of same-different responses (Experiment 1b). Stimuli were more easily discriminated following intermixed than following blocked preexposure on both the generalization and same-different tasks. This suggests that two stimuli are more perceptually distinct after intermixed preexposure. Experiments 2a and 2b investigated the mechanisms responsible for perceptual learning using same-different tasks. The results support the suggestion that the enhanced discrimination observed after intermixed preexposure is due to increases in the salience of the unique elements.     

On a class of additive learning models: Error-correcting and probability matching

A general model for learning signal detection in a Yes-No task is considered in which (a) the decision criterion shifts upward and downward by equal steps, and (b) the probability that the criterion shifts on a trial depends on the stimulus-response pair on that trial. Conditions are given for this process to have a unique stationary distribution, and the behavior of the process, as the step-size decreases to zero, is studied. The special model where criterion shifts may occur only on error trials can account for the probability matching behavior and for the interaction between signal strength and signal probability typically observed when the payoff matrix is symmetrical. Further, when the shift probability is assumed to be an increasing function of the distance of the sensory input from the criterion, the stationary mean criterion values are less extreme than the values that yield probability matching. It is shown that the model provides a way of incorporating payoff matrix asymmetry. Finally, the standard error in the maximum likelihood parameter estimates is calculated and a statistic is proposed for discriminating the error-correcting model from the more general model.     

The perceptual factor

A further study of the perceptual factor, previously isolated in a factor analysis of a battery of fifty-six tests, is made in a manner designed also to determine whether the same seven primaries would be found in a different population of subjects and with another battery of tests. The tests are described, and the results of the analysis are given in detail. Much attention is given to the matter of the orthogonality of primary factors and to their psychological meaningfulness.     

Cross-dimensional perceptual selectivity

Three visual search experiments tested whether top-down selectivity toward particular stimulus dimensions is possible during preattentive parallel search. Subjects viewed multielement displays in which two salient items, each unique in a different dimension--that is, color and intensity (Experiment 1) or color and form (Experiments 2 and 3)--were simultaneously present. One of the dimensions defined the target; the other dimension served as distractor. The results indicate that when search is performed in parallel, top-down selectivity is not possible. These findings suggest that preattentive parallel search is strongly automatic, because it satisfies both the load-insensitivity and the unintentionality criteria of automaticity.     

Visual perceptual learning

Perceptual learning refers to the phenomenon that practice or training in perceptual tasks often substantially improves perceptual performance. Often exhibiting stimulus or task specificities, perceptual learning differs from learning in the cognitive or motor domains. Research on perceptual learning reveals important plasticity in adult perceptual systems, and as well as the limitations in the information processing of the human observer. In this article, we review the behavioral results, mechanisms, physiological basis, computational models, and applications of visual perceptual learning.     

Induced perceptual grouping

ABSTRACT— The term perceptual grouping is associated with classical principles such as similarity and proximity. This article reports induced perceptual grouping, a phenomenon that occurs when placement of a uniform set of items near a structured set induces grouping within the otherwise uniform set. For example, when items grouped pair-wise by similarity are placed near another set of unstructured items, an analogous pair-wise grouping links elements of the second set. Induced grouping affected reaction times in two different visual search tasks, with reaction times depending on whether the target properties were contained within a group or crossed group boundaries as defined by induced grouping due to similarity, proximity, or common fate. Induced grouping was reduced when grouping between the structured and unstructured sets was weakened by means of a common-region cue or decreased similarity. Induced grouping appears to reflect the computation of hierarchical structure in visual images.