视时距知觉适应后效的空间选择性

时距知觉适应后效是指长时间适应于某一特定时距会导致个体对后续时距产生知觉偏差。其中对视时距知觉适应后效空间选择性的探讨存在争议,有研究支持位置不变性,也有研究支持位置特异性。这类研究能有效揭示时距编码的认知神经机制,位置不变性可能意味着时距编码位于较高级的脑区,而位置特异性则可能意味着时距编码位于初级视觉皮层。未来还可以探究时距知觉适应后效的视觉坐标表征方式,开展多通道研究以及相应的神经基础研究。     

Modifying an underlying component of perceived arm length: adaptation of tactile location induced by spatial discordance

In four experiments we examined the adaptation and aftereffect that resulted from a treatment yielding tactile/kinesthetic length discordance between the arms. Perceived discordance diminished with trials and tended to zero. Subsequent visual/tactile cross-modal judgments of distance showed the aftereffect to be a change in the perceived location of an unseen probed spot on each hand with respect to the location of a truly coincident visual marker. This occurred toward the body for the probed spot on one arm and away from the body on the other. There were three other main findings: (a) Arm movement was not a necessary condition for adaptation or aftereffect; (b) with intrinsic length information about the right arm present, but touch information from the right index finger absent during treatment, adaptation and aftereffect were abolished; (c) aftereffects of tactile location that were manifest at the hand and wrist tended to zero when a point close to the elbow was tested with a cross-modal procedure. The experiments provide evidence that the mapping of the tactile sheet onto an internal length domain had been modified by the treatment. The sensory consequences of the treatment led many subjects to report spontaneously that their arms felt to be of different lengths.     

The use of aftereffects in the study of relationships among emotion categories

The perception of visual aftereffects has been long recognized, and these aftereffects reveal a relationship between perceptual categories. Thus, emotional expression aftereffects can be used to map the categorical relationships among emotion percepts. One might expect a symmetric relationship among categories, but an evolutionary, functional perspective predicts an asymmetrical relationship. In a series of 7 experiments, the authors tested these predictions. Participants fixated on a facial expression, then briefly viewed a neutral expression, then reported the apparent facial expression of the 2nd image. Experiment 1 revealed that happy and sad are opposites of one another; each evokes the other as an aftereffect. The 2nd and 3rd experiments reveal that fixating on any negative emotions yields an aftereffect perceived as happy, whereas fixating on a happy face results in the perception of a sad aftereffect. This suggests an asymmetric relationship among categories. Experiments 4-7 explored the mechanism driving this effect. The evolutionary and functional explanations for the category asymmetry are discussed.     

Checkerboard-specific color aftereffects: A failure to find effects of perceptual organization

Two experiments investigated the effects of differing perceptual organizations of reversible figures on McCollough aftereffects. Experiment 1 used colored checkerboard inducing stimuli and achromatic grating test stimuli. While some subjects tended to organize the checkerboards into rows and/or columns and others to organize them into obliques, these variations did not result in differences in aftereffect direction or magnitude. Experiment 2 induced an aftereffect with colored gratings and tested with checkerboards, gratings, and a reversible concentric octagon pattern. Perceptual organization had no effect on results for checkerboards, but was related to aftereffect strength for the octagon pattern. Indirect evidence suggests that, in the latter case, differences in aftereffect strength may have influenced the perceived organization, rather than vice versa. Finally, regardless of the specific organization perceived, spontaneous viewing of all test stimuli produced stronger aftereffects than were found when subjects reorganized the pattern. This may have resulted from a viewing strategy associated with reorganization, since similarly small aftereffects were found when subjects concentrated their attention on a single pattern element.     

Aftereffects and the representation of stereoscopic surfaces

The structure of human disparity representation is examined through (i) adaptation experiments and (ii) model simulations of the data. Section 3 presents results of adaptation experiments designed to illuminate the structure of human disparity representation. Section 4 presents model simulations of three different disparity representation schemes. In the experiments, participants adapted to a 0.133 cycle deg-1 sinusoidally corrugated surface with 10 min of arc peak-to-trough disparity. A flat test surface was briefly presented, in which the aftereffect surface was perceived. Adapt and test surfaces were placed on disparity pedestals and thus presented in front of or behind the plane of fixation. The adapt surface could be offset from the fixation plane by +/- 8 to 24 min of arc. The test surface could be offset from the fixation plane by +/- 8 to 48 min of arc. The depth aftereffect was measured in different disparity planes by a nulling method and 'topping-up' procedure. Aftereffect tuning functions were obtained whose bandwidths, magnitudes, and tuning depended on the disparity planes of both the adapt and test surfaces. These parameters were used to constrain the models tested in section 4. On the basis of the two studies, it is argued that the human stereoscopic system encodes spatial changes of disparity using channels localised within disparity planes. A localised disparity-gradient model of the human representation of disparity is proposed.     

Interaction between perceived and imagined rotation

In Experiment 1, subjects performed a mental-rotation task in which they were timed as they decided whether rotated letters were normal or backwards. Between presentations of the letters, they watched a rotating textured disk that induced an aftereffect of rotary movement on the letters. The function relating reaction times to orientation was influenced asymmetrically by the aftereffect, suggesting that perceived movement interacts with imagined movement. Experiment 2 showed that the aftereffect produced a negligible influence on perceived orientation, suggesting that the influence of the aftereffect on mental rotation was not caused by changes in the perceived orientations of the letters. Detailed analysis of the mental-rotation functions suggested that the aftereffect may sometimes have induced subjects to rotate letters through the larger rather than the smaller angle back to the upright where the aftereffect was in the appropriate direction.     

Motion adaptation shifts apparent position without the motion aftereffect

Adaptation to motion can produce effects on both the perceived motion (the motion aftereffect) and the position (McGraw, Whitaker, Skillen, & Chung, 2002; Nishida & Johnston, 1999; Snowden, 1998; Whitaker, McGraw, & Pearson, 1999) of a subsequently viewed test stimulus. The position shift can be interpreted as a consequence of the motion aftereffect. For example, as the motion within a stationary aperture creates the impression that the aperture is shifted in position (De Valois & De Valois, 1991; Hayes, 2000; Ramachandran & Anstis, 1990), the motion aftereffect may generate a shift in perceived position of the test pattern simply because of the illusory motion it generates on the pattern. However, here we show a different aftereffect of motion adaptation that causes a shift in the apparent position of an object even when the object appears stationary and is located several degrees from the adapted region. This position aftereffect of motion reveals a new form of motion adaptation--one that does not result in a motion aftereffect--and suggests that motion and position signals are processed independently but then interact at a higher stage of processing.     

Aftereffect of high-speed motion.

A visual illusion known as the motion aftereffect is considered to be the perceptual manifestation of motion sensors that are recovering from adaptation. This aftereffect can be obtained for a specific range of adaptation speeds with its magnitude generally peaking for speeds around 3 deg s-1. The classic motion aftereffect is usually measured with a static test pattern. Here, we measured the magnitude of the motion aftereffect for a large range of velocities covering also higher speeds, using both static and dynamic test patterns. The results suggest that at least two (sub)populations of motion-sensitive neurons underlie these motion aftereffects. One population shows itself under static test conditions and is dominant for low adaptation speeds, and the other is prevalent under dynamic test conditions after adaptation to high speeds. The dynamic motion aftereffect can be perceived for adaptation speeds up to three times as fast as the static motion aftereffect. We tested predictions that follow from the hypothesised division in neuronal substrates. We found that for exactly the same adaptation conditions (oppositely directed transparent motion with different speeds), the aftereffect direction differs by 180 degrees depending on the test pattern. The motion aftereffect is opposite to the pattern moving at low speed when the test pattern is static, and opposite to the high-speed pattern for a dynamic test pattern. The determining factor is the combination of adaptation speed and type of test pattern.     

Simple and contingent aftereffects of perceived duration in vision and audition

After repeated presentations of a long inspection tone (800 or 1,000 msec), a test tone of intermediate duration (600 msec) appeared shorter than it would otherwise appear. A short inspection tone (200 or 400 msec) tended to increase the apparent length of the intermediate test tone. Thus, a negative aftereffect of perceived auditory duration occurred, and a similar aftereffect occurred in the visual modality. These aftereffects, each involving a single sensory dimension, aresimple aftereffects. The following procedures producedcontingent aftereffects of perceived duration. A pair of lights, the first short and the second long, was presented repeatedly during an inspection period. When a pair of test lights of intermediate duration was then presented, the first member of the pair appeared longer in relation to the second. A similar aftereffect occurred in the auditory modality. In these latter aftereffects, the perceived duration of a test light or tone is contingent—dependent—on its temporal order, first or second, within a pair of test stimuli. An experiment designed to test the possibility of cross-modal transfer of contingent aftereffects between audition and vision found no significant cross-modal aftereffects.     

Pulling faces: an investigation of the face-distortion aftereffect

After adaptation to a face distorted to look unnaturally thin or fat, a normal face appears distorted in the opposite direction (Webster and MacLin 1999 Psychonomic Bulletin & Review 6 647-653). When the adapting face is oriented 45 degrees from vertically upright and the test face 45 degrees in the opposite direction, the axis of perceived distortion changes with the orientation of the face. The magnitude of this aftereffect shows a reduction of approximately 40% from that found when both adapting and test faces are tilted identically. This finding suggests that to a large degree the aftereffect is mediated not by low-level retinotopic (image-based) visual mechanisms but at a higher level of object-based processing. Aftereffects of a similar magnitude are obtained when adapting and test images are both either upright or inverted, or for an upright adapter and an inverted test; but aftereffects are smaller when the adapter is inverted and the test upright. This pattern of results suggests that the face-distortion aftereffect is mediated by object-processing mechanisms including, but not restricted to, configurational face-processing mechanisms.     

Discontinuity of seen motion reduces the visual motion aftereffect

Would a motion-picture film of a rotating spiral induce a spiral aftereffect? This question was studied in two experiments in which Ss viewed an animated film of circles collapsing to a point. The rate of apparent motion of the collapsing circles and the discontinuity of motion—the length of jump between successively projected circles—were varied independently. A visual aftereffect like the spiral aftereffect was created. The aftereffect increased in strength and duration with the rate of motion, but at all rates of motion it declined as discontinuity of motion increased. The results are taken as evidence that motion aftereffects are caused by selective fatigue of small, directionally sensitive motion-receptive fields.     

Rapid discrimination of McCollough effects.

The McCollough effect is a colour aftereffect that is contingent on pattern orientation. Three experiments were conducted to establish whether such aftereffect colours could serve as a basis for discrimination in several rapid discrimination tasks. In the first experiment it was investigated whether aftereffect colours could act like a simple 'feature' in a visual search task involving a difficult orientation discrimination. Without McCollough adaptation, the time taken to detect a 'target' among 'distractors' increased substantially as the number of distractors increased. With adaptation, detection time was essentially independent of the number of distractors, indicating that the nature of the task changed from a difficult orientation discrimination to a simple discrimination based on differences in aftereffect colours. The second and third experiments employed a difficult four-alternative forced-choice procedure in which subjects were required to discriminate a monochromatic patch of square-wave grating oriented at 45 degrees from three others oriented at 135 degrees (and vice versa). The gratings were presented very briefly (67-333 ms) followed by a 500 ms mask. Subjects performed the task with and without McCollough adaptation. Performance was strikingly better after adaptation: colour aftereffects could be used to make the discrimination even at exposure durations as short as 67 ms. The third experiment demonstrated that this enhanced performance was indeed due to perceived colour differences (rather than a possible contrast difference). The results of the three experiments are discussed in relation to proposals about the locus of the McCollough effect.     

Orientation constancy of the McCollough effect

Two different techniques were used to determine the orientation constancy of orientation-contingent color aftereffects, McCollough effects. The results from both investigations agree and indicate That the aftereffect fails to exhibit orientation constancy other than that which can be explained by ocular countertorsion. Thus, the retinal rather than phenomenal orientation of the adaptation stimuli appears to be the determinant of aftereffect orientation. In fact, it is concluded that the aftereffect can be used to accurately monitor torsional eye position over long periods of time.     

Attentional modulation of the visual motion aftereffect has a central cognitive locus: evidence of interference by the postcategorical on the precategorical

An attentionally demanding task undertaken during adaptation to motion reduces the duration of the subsequent motion aftereffect (A. Chaudhuri, 1990). Previous studies have suggested that this effect is intramodal in character, reflecting the selective deployment of visual attention. The present study demonstrates that nonvisual tasks, performed concurrently with motion adaptation, can significantly reduce the duration of the ensuing aftereffect. Three experiments converge on the conclusionthat postcategorical processes can influence otherwise unrelated concurrent precategorical processes. The experiments also show that neither perceptual input nor motor output components of the attentional task are responsible for the subsequent reduction in motion of aftereffect. The results suggest a reappraisal of findings in this area and of the general distinction between perception and cognition.     

Effect of the standard on size of the horizontal-vertical illusion

70 subjects participated in a study designed to replicate the 1968 claim of Gardner and Long that the horizontal-vertical illusion is larger with the vertical than with the horizontal as standard. The effect did not appear in Exp. 1 when subjects made judgments under both the reproduction and graded-series methods but did in a pilot study and in Exp. 2, although more strongly with the method of reproduction.     

Eye direction aftereffect

Three experiments using computer-generated human figures showed that after a prolonged observation of eyes looking to the left (or right), eyes looking directly toward the viewer appeared directed to the right (or left). Observation of an arrow pointing left or right did not induce this aftereffect on the perceived eye direction. Happy faces produced the aftereffect more effectively than surprised faces, even though the image features of the eyes were identical for both the happy and the surprised faces. These results suggest that the eye direction aftereffect may reflect the adaptation of relatively higher-level mechanisms analyzing the others eye direction.     

The effects of verbal cueing on implicit hand maps

The use of position sense to perceive the external spatial location of the body requires that immediate proprioceptive afferent signals be combined with stored representations of body size and shape. Longo and Haggard (2010) developed a method to isolate and measure this representation in which participants judge the location of several landmarks on their occluded hand. The relative location of judgements is used to construct a perceptual map of hand shape. Studies using this paradigm have revealed large, and highly stereotyped, distortions of the hand, which is represented as wider than it actually is and with shortened fingers. Previous studies using this paradigm have cued participants to respond by giving verbal labels of the knuckles and fingertips. A recent study has shown differential effects of verbal and tactile cueing of localisation judgements about bodily landmarks (Cardinali et al., 2011). The present study therefore investigated implicit hand maps measuring through localisation judgements made in response to verbal labels and tactile stimuli applied to the same landmarks. The characteristic set of distortions of hand size and shape were clearly apparent in both conditions, indicating that the distortions reported previously are not an artefact of the use of verbal cues. However, there were also differences in the magnitude of distortions between conditions, suggesting that the use of verbal cues may alter the representation of the body underlying position sense.     

Implicit body representations and the conscious body image

Recent studies have revealed that somatosensory processing relies on a class of implicit body representations showing large distortions of size and shape. The relation between these representations and the conscious body image remains unclear. Dissociations have been reported in the clinical literature on eating disorders between different body image measures, with larger and more consistent distortions found with depictive measures, in which participants compare their body to a visual depiction of a body, than metric measures, in which participants compare their body to some non-body standard. Here, we compared implicit body representations underlying position sense to the body image measured with both depictive and metric methods. The body image was measured using both a depictive method (template matching) in which participants judged whether their hand was wider or more slender than a shown hand picture, and a metric method (line length) in which participants judged whether different parts of their hand were shorter or longer than a presented line. Consistent with previous findings, characteristic distortions were found for the implicit body representation underlying position sense. These distortions were also found in attenuated form for metric - but not depictive - body image measures. While replicating the basic dissociation between implicit body representations and the conscious body image, these results demonstrate that this dissociation is not absolute and specific tasks may utilise both to varying degrees depending on task demands. Metric measures may not be pure measures of body image, but some combination of visual and somatosensory body representations.     

Adaptation to telestereoscopic viewing measured by one-handed ball-catching performance

A one-handed ball-catching task was used to study the disturbance of depth judgement induced by telestereoscopic viewing (ie viewing with increased effective interocular separation), the recovery of performance with experience in the telestereoscope, and the errors that subsequently arose when the telestereoscope was removed. The ball's trajectory was variable so that subjects had to control both the position and the timing of the grasp in order to catch the ball. On first wearing the telestereoscope, subjects closed the hand when the ball was approximately twice as far away from the eyes as the hand was. After fewer than twenty trials in the telestereoscope subjects were closing the hand at approximately the correct time and place, although rather more trials were needed for ball-catching performance to recover to normal. When the telestereoscope was removed there was an aftereffect, with subjects making the opposite errors to when they began the task. The existence of an aftereffect shows that the process of adaptation involves reevaluation rather than neglect of the misleading binocular information. Helmholtz's theory that telestereoscopes cause the world to be perceived as a scale model is considered. Initial misreaching is roughly consistent with this theory, but there are insufficient data to test it rigorously. Data from the aftereffect phase are clearly inconsistent with the theory. The results confirm the importance of binocular information in dynamic motor tasks, such as ball catching.     

The associative basis of contingent color aftereffects.

According to a conditioning analysis of the orientation-contingent color aftereffect (McCollough effect, ME), orientation stimulus (grids) become associated with color. Contrary to this interpretation are reports that simple forms cannot be used to elicit illusory color and that the ME is not degraded by decreasing the grid-color correlation. The present results indicate: (a) Form stimuli can contingently elicit color aftereffects; (b) even a non-patterned stimulus--the lightness of a frame surrounding a colored area--can contingently elicit color aftereffects; (c) this frame lightness-contingent aftereffect, like the ME, persists for at least 24 hr; and (d) the frame lightness-contingent aftereffect can be used to demonstrate that correlational manipulations affect the ME, as they affect other types of conditional responses.