Grouping in the shine-through effect

How the elements of a visual scene are grouped into objects is one of the most fundamental but still poorly understood questions in visual neuroscience. Most investigations of perceptual grouping focus on static stimuli, neglecting temporal aspects. Using a masking paradigm, we show that the neural mechanisms underlying grouping seem to be both fast and complex. For example, a vernier target was followed by, first, a briefly presented grating and, then, a long-lasting, extended grating. Under these conditions, the briefly presented grating is hardly visible. Still, vernier discrimination strongly changed with the number of elements of the briefly displayed grating being worst for small gratings. In accordance with a neural network model of masking, we propose that the edges of the briefly presented grating and the vernier interfere in spite of the short presentation time. We suggest that this fast edge processing is a first step for unconscious grouping processes.     

Local and global mechanisms of one- and two-dimensional orientation illusions

One-dimensional (1-D) orientation illusions induced on a test grating by a tilted and-surrounding 1-D inducing grating have a well-known angular function that exhibits both repulsion and attraction effects. Two-dimensional (2-D) orientation illusions are those induced on a test grating by 2-D image modulation, such as a pair of superimposed inducing gratings at different orientations, usually orthogonal (a plaid). Given the known angular functions induced by the plaid component gratings, two hypotheses were developed that predicted different plaid-induced illusion functions. Hypothesis 1 states that the 1-D component-induced effects simply add linearly; Hypothesis 2 states that there is an additional mechanism that responds to the virtual axes of mirror symmetry of the plaid and adds to the effect. The data of two experiments were consistent with the predictions from the second hypothesis but not the first. Possible neural substrates of mechanisms that extract axes of symmetry are discussed; it is suggested that such global symmetry axes may underlie the perceived orientation of complex shapes.     

Local and global mechanisms of one- and two-dimensional orientation illusions.

One-dimensional (1-D) orientation illusions induced on a test grating by a tilted and surrounding 1-D inducing grating have a well-known angular function that exhibits both repulsion and attraction effects. Two-dimensional (2-D) orientation illusions are those induced on a test grating by 2-D image modulation, such as a pair of superimposed inducing gratings at different orientations, usually orthogonal (a plaid). Given the known angular functions induced by the plaid component gratings, two hypotheses were developed that predicted different plaid-induced illusion functions. Hypothesis 1 states that the 1-D component-induced effects simply add linearly; Hypothesis 2 states that there is an additional mechanism that responds to the virtual axes of mirror symmetry of the plaid and adds to the effect. The data of two experiments were consistent with the predictions from the second hypothesis but not the first. Possible neural substrates of mechanisms that extract axes of symmetry are discussed; it is suggested that such global symmetry axes may underlie the perceived orientation of complex shapes.     

Panum’s fusional area estimated with a criterion-free technique

It has been reported that criterion-free estimates of the upper disparity limits for fusion of line targets are small enough to be accounted for by monocular vernier sensitivity. However, targets such as lines, which contain high spatial frequencies, may ensure small fusion limits, since fusion limits obtained with criterion-dependent methods for narrow-band targets, such as sinusoids or difference-of-Gaussian luminance profiles, are proportional to target spatial periods. Experiment 1 therefore explored whether criterion-free methods give fusion limits for narrow-band targets that can be accounted for by vernier sensitivity. Vertical fusion limits were estimated by a method that forced observers to discriminate a disparate sinusoidal grating from an immediately adjacent zero-disparity grating. Fusion limits were too large to be explained by monocular vernier thresholds obtained for the same targets. In addition, fusion limits were not affected by large changes in target contrast, whereas vernier thresholds increased as contrast was decreased. The results of Experiment 1 also argued against interocular suppression as the cause of single vision, since vernier offsets that were visible when viewed monocularly were invisible under binocular viewing conditions. In Experiment 2, manual adjustment of disparities yielded fusion limits little different from those obtained with the forced-choice method of Experiment 1, demonstrating that it is possible to design adjustment methods for assessing fusion limits that are as sensitive as forced-choice methods. In Experiment 3, large reductions in target contrast, which have the effect of decreasing disparity sensitivity, did not alter fusion limits, disconfirming the idea that fusion limits estimated with discriminative procedures represent disparity-detection thresholds. In Experiment 4, disparities were adjusted until a just noticeable difference in grating contrast appeared. These disparities were larger than fusion limits, indicating that fusion limits did not represent a change in apparent contrast arising from disparity limitations of binocular summation. Together, the four experiments support the existence of binocular fusion as a unique category of sensory performance, disconfirm several nonfusional explanations of single vision, and support the use of criterion-free as well as adjustment methods in measuring fusion limits.     

Panum's fusional area estimated with a criterion-free technique

It has been reported that criterion-free estimates of the upper disparity limits for fusion of line targets are small enough to be accounted for by monocular vernier sensitivity. However, targets such as lines, which contain high spatial frequencies, may ensure small fusion limits, since fusion limits obtained with criterion-dependent methods for narrow-band targets, such as sinusoids or difference-of-Gaussian luminance profiles, are proportional to target spatial periods. Experiment 1 therefore explored whether criterion-free methods give fusion limits for narrow-band targets that can be accounted for by vernier sensitivity. Vertical fusion limits were estimated by a method that forced observers to discriminate a disparate sinusoidal grating from an immediately adjacent zero-disparity grating. Fusion limits were too large to be explained by monocular vernier thresholds obtained for the same targets. In addition, fusion limits were not affected by large changes in target contrast, whereas vernier thresholds increased as contrast was decreased. The results of Experiment 1 also argued against interocular suppression as the cause of single vision, since vernier offsets that were visible when viewed monocularly were invisible under binocular viewing conditions. In Experiment 2, manual adjustment of disparities yielded fusion limits little different from those obtained with the forced-choice method of Experiment 1, demonstrating that it is possible to design adjustment methods for assessing fusion limits that are as sensitive as forced-choice methods. In Experiment 3, large reductions in target contrast, which have the effect of decreasing disparity sensitivity, did not alter fusion limits, disconfirming the idea that fusion limits estimated with discriminative procedures represent disparity-detection thresholds. In Experiment 4, disparities were adjusted until a just noticeable difference in grating contrast appeared. These disparities were larger than fusion limits, indicating that fusion limits did not represent a change in apparent contrast arising from disparity limitations of binocular summation. Together, the four experiments support the existence of binocular fusion as a unique category of sensory performance, disconfirm several nonfusional explanations of single vision, and support the use of criterion-free as well as adjustment methods in measuring fusion limits.     

Late maturation of visual hyperacuity

We used a visual evoked–potential measure to study the development of two components of pattern vision, vernier acuity and grating acuity, in humans from early infancy through adolescence. These two visual functions develop at similar rates and have nearly the same absolute values between 1 month and 6 years of age. After age 6, grating acuity is constant at the adult level, but vernier acuity continues to improve, becoming a hyperacuity. Vernier acuity reaches asymptotic levels around age 14 years. These results suggest that adultlike vernier hyperacuity is not limited by spatial resolution or sensitivity of small receptive fields, but rather that the limitation is imposed by higher–level processing. Sensitivity, connections in visual cortical areas, or both therefore retain plasticity throughout childhood and into adolescence.     

Priming of pop-out: I. Role of features

We examined a visual search task, in which observers responded to the high-acuity aspect of a popout target (shape of an odd-colored diamond or vernier offset of an odd spatial-frequency patch). Repetition of the attention-driving feature (color or spatial frequency) in this task primes the popout; repetition of the high-acuity aspect (shape, vernier offset) does not. Priming of pop-out is due to a decaying memory trace of the attention-focusing feature laid down with each trial. The trace exerts a diminishing effect over the following five to eight trials (≈30 sec), and its influence over this time is cumulative. Observers cannot willfully overcome the priming, which suggests that it is passive and autonomous. Both target facilitation and distractor inhibition are evident; the former has a greater effect. The phenomenon shows complete binocular transfer.     

Features of the selectivity for contrast polarity in contour integration revealed by a novel tilt illusion

We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.     

Strange-face illusions during inter-subjective gazing

In normal observers, gazing at one’s own face in the mirror for a few minutes, at a low illumination level, triggers the perception of strange faces, a new visual illusion that has been named ‘strange-face in the mirror’. Individuals see huge distortions of their own faces, but they often see monstrous beings, archetypal faces, faces of relatives and deceased, and animals. In the experiment described here, strange-face illusions were perceived when two individuals, in a dimly lit room, gazed at each other in the face. Inter-subjective gazing compared to mirror-gazing produced a higher number of different strange-faces. Inter-subjective strange-face illusions were always dissociative of the subject’s self and supported moderate feeling of their reality, indicating a temporary lost of self-agency. Unconscious synchronization of event-related responses to illusions was found between members in some pairs. Synchrony of illusions may indicate that unconscious response–coordination is caused by the illusion–conjunction of crossed dissociative strange-faces, which are perceived as projections into each other’s visual face of reciprocal embodied representations within the pair. Inter-subjective strange-face illusions may be explained by the subject’s embodied representations (somaesthetic, kinaesthetic and motor facial pattern) and the other’s visual face binding. Unconscious facial mimicry may promote inter-subjective illusion–conjunction, then unconscious joint-action and response–coordination.     

The influence of age, sex, and specialized training on the vertical-horizontal illusion

With the aim of investigating the perceptual processes responsible for perceptual illusions, we have studied the influence of age, sex and specialized training on two forms of the vertical-horizontal illusion. In Figure A, the vertical is a short distance away from the horizontal; in Figure B, the vertical meets the horizontal segment at its mid-point. Both figures were presented in brief (0-2 second) and long (I-o second) tachistoscopic exposure, and in unlimited exposure.

When time is unlimited. Illusion A increases up to 9-10 years and then remains constant and Illusion B decreases as a function of age and chiefly as a function of the degree of scientific training. The illusions are stronger in tachistoscopic perception than under conditions of umlimited exposure. Both illusions also increase in tachistoscopic perception with age except for science students. Under condition of unlimited time, women have stronger illusions than men. This difference does not occur in tachistoscopic perception.

These results may be interpreted in terms of the interaction of three processes: interaction among the elements of a figure (field effects); perceptual activity which makes possible the passing from syncretism or multiplicity to organized perception; and the activity of measuring the elements relatively to each other. This latter activity develops with cultural level and especially with scientific training. It is more effective with men than with women, due, it is suggested, to the spatial factor being higher in men.     

视觉工作记忆中特征绑定关系的记忆机制

弱客体理论认为, 视觉工作记忆系统是由众多特征存储的子系统组成, 不同纬度的特征独立存储在相应的有限容量的子系统中, 相互之间不会竞争记忆资源。而对于特征之间绑定关系的记忆存在不同的观点。一种观点认为绑定关系的记忆需要注意维持, 因此绑定关系的记忆会占用到特征记忆的资源; 另一种观点认为绑定关系的记忆是自动发生的, 不需要注意的维持。本实验的目的是探究特征绑定关系的记忆是否是自动发生的。在实验中, 我们设计了两种任务, 一种任务是只记忆颜色, 另一种任务是记忆颜色跟位置及其之间的绑定关系, 并测试分析视觉工作记忆相关的ERP成分CDA。结果发现两种任务条件下的CDA波幅之间没有显著差异, 说明视觉工作记忆中的特征绑定是自动发生的。     

Silencing the experience of change

Perceptual illusions have often served as an important tool in the study of perceptual experience. In this paper I argue that a recently discovered set of visual illusions sheds new light on the nature of time consciousness. I suggest the study of these silencing illusions as a tool kit for any philosopher interested in the experience of time and show how to better understand time consciousness by combining detailed empirical investigations with a detailed philosophical analysis. In addition, and more specifically, I argue against an initially plausible range of views that assume a close match between the temporal content of visual experience and the temporal layout of experience itself. Against such a widely held structural matching thesis I argue that which temporal changes we are experiencing bears no close relation to how our experience itself is changing over time. Explanations of the silencing illusions that are compatible with the structural matching thesis fail.     

Orientation illusions induced by briefly flashed plaids

Orientation illusions which occur when a vertical grating is surrounded by a plaid can be induced either by one of the plaid's orthogonal component gratings or by a virtual axis of symmetry of the plaid, whichever is nearest vertical. In six experiments in which such illusion displays were flashed for durations between 15 and 405 ms, it was found that when these two-dimensional illusions are induced by a component grating (direct effects) the illusions increase monotonically as duration decreases, from 1 degree-2 degrees to about 6 degrees-7 degrees, over this range. Effects induced by axes of symmetry (indirect effects), in contrast, begin to occur only at longer durations: for short exposures, illusions are directionally opposite and large, similar to direct effects. These results suggest that only plaid-component-selective mechanisms operate at the shortest exposure durations and that additional time is required to extract more global higher-order pattern structure. The data are discussed in relation to sustained and transient mechanisms and also with respect to recent reports of more global processing mechanisms in extrastriate cortex and related data on one-dimensional tilt illusions.     

From visual acuity to hyperacuity: a 10-year update

Visual acuity, the most basic measure of developing pattern vision in human infants, has been used extensively for detecting anomalies of vision and oculomotor coordination. In the past 10 years much has been learned about the development of two hyperacuities, namely, vernier acuity and stereoacuity. These two acuities become superior to grating acuity after the third month and remain so throughout life. Compared to females, males show slower development of stereopsis and vernier acuity, but not grating acuity, during the third through sixth months. We have suggested that this may result from the neurotrophic effects of the early pulse of testosterone found in males. Measures of vernier acuity have proven effective in detecting meridional amblyopia in older children who had significant astigmatism in the first year and subsequently lost it. The susceptible period for acquiring meridional amblyopia extends from the second half of the first year to at least the end of the second year. Deviations from the typical oblique effect (equal acuity for vertical and horizontal edges; equal, but lower, acuity for left oblique and right oblique) may result from uncorrected astigmatism early in life.     

This I Have Learned from Over 40 Years of Personality Research

ABSTRACT During the over 40 years in which I have conducted personality research, I have had a number of insights about the research process that I thought would be worth sharing: an awareness of the human side of science; lessons from the person-situation debate; lessons from comparing research on highly ego-involving natural events, such as sport parachuting, with laboratory analogues; the realization of what is wrong with the concept of the Freudian unconscious and what should be done to replace it; and awareness of pervasive biases in the journal-reviewing process. Perhaps the one most general lesson I have learned is that the advancement of psychology as a cumulative, integrative science is hampered not so much by its conceptual complexity as by the difficulty of humankind to view itself objectively, with honesty, courage, and a willingness to surrender illusions.     

A new visual illusion, and its mechanism

A new visual illusion is reported, in which a sine-wave grating appears to tilt when doubly sheared perpendicularly to the grating lines. It is shown that the illusory percept is related to the Münsterberg and Café Wall illusions. The probable mechanism at the root of all such illusions is postulated by reference to the neuroarchitecture of the retina and striate cortex.     

Perception: A HyperCard stack for demonstrating visual perceptual phenomena

Perception is a HyperCard stack that allows users to explore visual illusions and other perceptual phenomena on the Apple Macintosh. The stack contains over 20 demonstrations of intersecting line illusions, size and shape illusions, subjective contours, color assimilation, and so forth. As a presentation tool for classroom or laboratory demonstrations, Perception offers three unique features for displaying visual phenomena: (1) the capability to “dissolve” the inducing elements of an illusion in order to show the objective state of affairs, (2) the ability to quickly reverse the inducing elements of an illusion and therefore the effects of the distortion, and (3) animation of the various components of an illusion to produce continuous distortions in-real time. These features are illustrated with use of the Orbison, Titchener, Hering, and Wundt illusions. Use of the stack reveals two interesting and unanticipated findings: (1) an apparent size distortion in the central square of the Orbison illusion as it moves back and forth across the background of concentric rings, and (2) perceptual aftereffects that arise when the inducing elements of the Titchener, Hering, or Wundt illusion is dissolved.     

The oblique effect in a vernier acuity situation

Observers viewed either vertical or obliquely oriented vernier targets from either an upright position or with their heads tilted. Vernier acuity was consistently better for retinally vertical than for gravitationally vertical targets, even when presented against a background context of vertical stripes designed to aid veridical perception of gravitational orientation. These results indicate that vernier acuity depends on retinal image orientation rather than on perceived orientation. The high contrast of the vernier lines ensures that their gravitational orientation is clearly perceived. Thus the present results provide a stronger basis for ruling out the effects of perceptual orientation than previous studies involving grating contrast-threshold measurements. Since the vernier targets were presented as brief flashes, it is unlikely that the measured oblique effect is attributable to differences in eye-movement patterns.     

A correlational analysis of symmetry between the arrowhead and featherhead Müller-Lyer illusions

Correlational methods were used to investigate symmetry of effect for the arrowhead and featherhead versions of the Müller-Lyer figure. Two control figures were compared in the determination of baseline levels for measurement of the illusions: a shaft presented without any inducing context, and a shaft with vertical inducing lines attached. In addition, results based on difference-score measures of the illusions were contrasted with results obtained by partial-correlation techniques. Overall, when one considers the results for either one of the arrowhead or featherhead versions, the evidence favours a common underlying mechanism. However, results across the two versions suggest that the mechanisms for the two versions differ fundamentally. In weighting the different kinds of evidence contributing to this conclusion, methodological issues were raised. By obtaining two judgments for each stimulus figure from a large number of subjects, it was possible to demonstrate not only that conventional difference-score measures of illusions are highly unreliable, but also that they can yield biased results.     

Vernier acuity as affected by target length and separation

Vernier acuity was measured for vertical lines of different lengths; the threshold (about 4 sec of arc) was almost as good for the shortest stimuli (1 min 20 sec squares) as for the longest (21 min 20 sec × 1 min 20 sec rectangles) and did not change when two round dots were shown in positions corresponding to the squares. The threshold for the two dots measured in terms of minimum detectable lateral offset increased when the vertical separation between the dots increased, but, when replotted in terms of the angle of tilt between them with respect to vertical, the threshold improved with dot separation; moreover, at asymptote, the threshold was comparable to that obtained for detecting that an actual line was tilted out of vertical. Our data suggest that, in performing the vernier task, Ss do not extrapolate the edges of the vernier elements; instead, they judge the deviation of the inner ends of the stimuli from verticality. This hypothesis explains the effect of increasing separation between vernier elements and also accounts for other types of acuity, such as the detection of curvature.