bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrimination of Stimulus Aperiodicity as a Function of Temporal Patterning: A Discrepancy between Psychophysical and Sensory—Neural Assessments
Authors: Lechelt Eugene C
Published: January 2007

Tactile discrimination of stimulus aperiodicity was investigated in a two-alternative forced-choice task by having subjects report which of two successively presented trains of mechanical pulses, one with complete pulse periodicity and one in which a single pulse was temporally displaced from its regular placement, was temporally irregular or aperiodic. Trains contained three, four, or five pulses and were presented at interpulse intervals of 60, 75, 85, 100, 125, and 150 ms. Aperiodic trains had one pulse, other than the first or last pulse, temporally advanced or receded by 40% of the interstimulus interval. Results showed that: (i) although the percentage of correct reports of aperiodicity decreased as presentation rate increased (smaller interpulse intervals), the amount of decrease was a function of the number of pulses in a train; (ii) the discrimination of aperiodicity was dependent upon the specific location of the irregularity within the stimulus temporal pattern; and (iii) all patterns with complete temporal reversals of their successive interpulse intervals yielded nearly equivalently accurate reports of aperiodicity. These data suggest that central, attentional factors are involved in the discrimination of stimulus aperiodicity.
The Effects of Duration and Luminance on Binocular Depth Mixture
Authors: Birch Eileen E , Foley John M
Published: January 2007

Two stimuli in the same binocular direction, one in front and the other an equal disparity behind a fixation point, are perceived at one depth. This depth is between that corresponding to the two stimulus disparities and varies continuously from one stimulus to the other as a function of the ratio of their luminances. When either duration or absolute luminance is increased, perceived depth changes toward the midpoint of the two disparities.
Interactions between Simultaneous Contrast and Adaptation to Gradual Change of Luminance
Authors: Anstis Stuart M
Published: January 2007

Following adaptation to a field of light which was modulated by a rising ramp so that it repetitively grows gradually brighter, a steady test field of light appears to be gradually growing dimmer. In this study, if a small grey spot of constant luminance was centred in the brightening field, it appeared to be growing gradually dimmer by simultaneous contrast. This apparent dimming led to a brightening aftereffect in the spot. It was shown that this spot aftereffect had two independent components: the apparent dimming of the adapting spot produced its own aftereffect (contrast produced an aftereffect) and also the dimming aftereffect in the surround field spatially induced an aftereffect into the spot during the test period (aftereffect produced simultaneous contrast). Thus simultaneous contrast can both precede and follow successive contrast in the visual system.
Development of the Perception of Invariants: Substance and Shape
Authors: Gibson Eleanor J , Owsley Cynthia J , Walker Arlene , Megaw-Nyce Jane
Published: January 2007

Three experiments investigated the perception of substance and shape as invariant properties of objects by three-month-old infants. In experiment 1, infants were habituated to two differently shaped objects undergoing a rigid motion. After habituation of the infants, the objects were presented undergoing a different rigid motion, or undergoing a deforming motion, or undergoing the same rigid motion. Habituation was maintained to the new rigid motion, indicating that the two rigid motions were perceived as sharing an invariant property. Dishabituation, on the other hand, occurred when a deforming motion followed a rigid one. In experiment 2, infants were habituated to one shape undergoing two different rigid motions. After habituation, the shape was changed but the same two motions continued. Dishabituation occurred, compared to a group with no shape change, indicating that shape is distinguished as an invariant property over two rigid motions. In experiment 3, habituation to a shape undergoing two rigid motions was followed by a new shape presented motionless, or the same shape presented motionless. Cessation of motion did not prevent recognition of shape as invariant. Two properties of an object, substance and shape, thus appear to be detectable as invariant in an event sequence, an instance of ‘phenomenal doubling’ at an early age.
Spatiotemporal Filtering and the Interpolation Effect in Apparent Motion
Authors: Morgan Michael J
Published: January 2007

A target moving in discrete spatial steps with an appropriate interstep interval (ISI) can appear visually as if it is in continuous motion. The momentary spatial position of such a target is interpolated by the observer between its real physical positions. The extent of this interpolation was measured by a vernier alignment technique, and was found to decrease as the ISI was lengthened.

A discretely moving target may be described as a continuously moving target on which is superimposed a periodic modulation of spatial position. It is shown that the traditional ‘staircase’ stimulus for apparent motion can be generalized to include other kinds of periodic modulation. With the use of various analog-filtered and digitally filtered versions of staircase stimuli with different ISIs, it was shown that the phenomenal interpolation of a periodically modulated moving target was affected only when the frequencies of modulation were less than about 25 Hz. The spatial amplitude of the modulation also has some effect.
An Invariant for Wheel-Generated Motions and the Logic of its Determination
Authors: Proffïtt Dennis R , Cutting James E
Published: January 2007

Observers appear to perceive the paths of abstract centers of point-light configurations in making judgments about movement. For configurations on rolling wheels a metric was derived that described the relative vertical motion of this point. It was hypothesized that the smaller the metric the more the stimulus should appear to move in a wheel-like manner with linear translation. In two experiments observers viewed pairs of stimuli and were asked to select either the event that appeared most wheel-like or the one that hopped the most. Viewers consistently selected the stimulus with the smaller metric as being more wheel-like, with a frequency that increased with the difference between metrics. The inverse of this pattern was found for those observers requested to select the stimulus that hopped most. In a second set of two experiments observers drew the translationl paths of these stimuli. Their drawings corresponded to the motion paths of configural centroids. Together, these results strongly suggest that observers perceive the translational component of the motion of the configurations as the path described by their centroids, or geometric centers. We propose that this description of the stimulus event is determined by the logical ordering of information extraction provided by the perceptual system, and discuss this logic and cases where it seems evident.
Effects of Posthypnotic Suggestion on Perceived Egocentric Distance
Authors: MacCracken Peter J , Gogel Walter C , Blum Gerald S
Published: January 2007

The effects of posthypnotic suggestion on the perception of egocentric distance were evaluated by two methods, one direct and the other indirect. The direct method was the verbal report of the perceived distance of the stimulus. The indirect method used a measure based on apparent concomitant motion of the stimulus with a lateral movement of the head. The indirect method, unlike the direct method, has been shown to be insensitive to cognitive biases. Two highly trained hypnotic observers received posthypnotic suggestions to see a point of light at approximately 2, 4, or 6 ft (61, 122, or 183 cm) from themselves. For each suggested distance the light was physically at 2, 4, or 6 ft. As a control, trials were completed using these same physical distances without the posthypnotic suggestions. Nine experimental trials, one for each combination of suggested distance and physical distance, constituted a trial set. One observer completed three sets, and the other completed two sets. It was found that the posthypnotic suggestions affected the direct but not the indirect measures of the perceived distances of the light.
Perception of an Illusory Triangle with Masked Inducing Figure
Authors: Gellatly Angus R H
Published: January 2007

Subjects viewed the Kanizsa triangle under conditions of visual masking. Depending on the type of mask employed, the triangle could be perceived when the inducing discs were not phenomenally present, or the discs could be seen with the triangle not present. These findings suggest that no single set of mechanisms, physiological or cognitive, will suffice to explain perception of the illusory triangle.
Use of Foreground and Background Information in Visually Guided Locomotion
Authors: Strelow Edward R , Brabyn John A
Published: January 2007

The effects of reducing the range of spatial perception on the accuracy of visually guided locomotion were studied in two experiments. Limiting the range of perception to only near objects produces changes in the flow of stimulus detail and reduces opportunities for the appearance of an aiming point and for motion parallax. Such conditions were found to produce inferior performance compared to full vision, or to minimal background information. A defined aiming point was also found to assist control when no other background was present. The results are discussed with reference to theories of locomotor control and the design of artificial spatial sensing aids for the blind.
Adaptation to the Reversal of Binocular Depth Cues: Effects of Wearing Left-Right Reversing Spectacles on Stereoscopic Depth Perception
Authors: Shimojo Shinsuke , Nakajima Yoshitaka
Published: January 2007

The principle of stereopsis, that crossed disparity causes a convex perception and uncrossed disparity a concave one, has for a long time been considered to depend on a very rigid neural mechanism not affected by experience. Experiments are reported here which show that this relationship between disparity and perceived depth can be reversed by experience. An observer wore a pair of left-right reversing spectacles continuously for nine days. The spectacles also reversed the relation between the direction of perceived depth and the direction of binocular depth cues, ie disparity and vergence. For a period starting two days before wearing the spectacles and continuing until seventy-nine days after their removal the observer was examined with a haploscope and an electrooculograph. All the stereoscopic experiments were carried out without spectacles in order to examine some aftereffects of wearing spectacles. For the stereograms with linear contours not only the adaptive reversal of the relation between disparity and perceived depth, but also some abnormal depth perceptions and long-lasting aftereffects were found. For Julesz's random-dot stereograms, however, in which contours can be seen only after binocular combination, no adaptive change or reversal occurred. These results suggest that the process of stereopsis consists of two concurrent subprocesses.
Random-Curve Stereograms: A Flexible Tool for the Study of Binocular Vision
Authors: Ninio Jacques
Published: January 2007

A random curve belonging to a surface can be used to portray that surface. The surface cannot be identified monocularly from projections of the random curve, but is easily reconstructed under stereoscopic viewing of two appropriate projections. Examples of this flexible alternative to Julesz's random-dot stereograms are presented.
Random-Dot Motion Displaces Ehrenstein Illusion
Authors: Spillmann Lothar , Redies Christoph
Published: January 2007

When a random-dot screen is used as a background for Ehrenstein figures, brightness enhancement is replaced by a change of grain and structure. Dots in the illusory area appear less densely packed and may be perceived as concentrically organized. When the screen is moved with respect to the Ehrenstein figures, the illusory patches seem to move in the same direction and out of the inducing area while maintaining their characteristic organization. It is proposed that neurophysiological mechanisms with different persistencies are involved in producing the observed phenomenon. It is also suggested that random dots moving along the same open path are combined into a figure, whereas dots crossing the lines of the pattern remain unstructured and serve as a ground against which the displacement is seen.
A New Bistable Motion Illusion Based upon ‘Kinetic Optical Occlusion’
Authors: Petersik J Timothy , McDill Melinda
Published: January 2007

A display was devised for the purpose of studying the information afforded by kinetic optical occlusion (the progressive erasure and replacement of static elements within a display). A microcomputer generated a series of equally spaced light bars on a dark background. The first bar on the left was suddenly blanked and, after a pause of variable duration (an interblank interval, or IBI), was replaced. As the first bar was replaced, the second bar in the series was blanked, and so on, until each bar in the pattern had been blanked and replaced. Depending upon the duration of the IBI, this display gave rise to one of two alternative percepts: the observer either saw movement of a dark shadow ‘in front of’ the pattern of bars (with IBIs ≲ 50 ms) or he saw right-to-left stroboscopic movement of successive bars (with IBIs ≳ 85 ms). At some intermediate IBI (the transition IBI) the display was bistable. A two-bar variant of the original display was also studied and found to be bistable under appropriate conditions. In a series of experiments it was found that the transition IBI for the original display did not depend upon whether the observer was tracking the sequence of events or fixating a stationary point in the display. The transition IBI was an increasing function of spatial frequency above about 3 cycles deg−1, and depended upon whether the display was focused or optically blurred. Empirically determined transition IBIs correspond well to estimates of the integration times of visual mechanisms studied in other paradigms.
The Neon Color Effect in the Ehrenstein Illusion
Authors: Redies Christoph , Spillmann Lothar
Published: January 2007

Van Tuijl's neon color effect arises in the Ehrenstein figure if a colored cross is added such as to connect the black arms across the central gap. The effect consists of a circular veil of color in the illusory area and has the same hue as the inducing cross. The neon-like coloration is uniform, or when elicited by two colors bipartite; it is strongest on backgrounds resembling the color of the cross. The effect cannot be attributed to chromatic aberration or eye movements. In foveal vision (and for red crosses) neon spreading is limited to gap sizes between 4 and 35 min of arc. Extrafoveally, gap sizes may be larger by a factor of two. Neon perception is enhanced by flicker and weakened if stimuli are oriented obliquely. It does not occur with dichoptic presentation. A maximum illusion requires that the Ehrenstein figure and cross are laterally and angularly aligned for good perceptual continuation. A neuronal origin by spreading and summation, together with cognitive processes, is proposed.
Meridional Differences in Temporal Resolution
Authors: Schwartz Barry D , Winstead Daniel K , May James G
Published: January 2007

Previous investigations of temporal resolution have shown that performance is influenced by a number of stimulus parameters. The interstimulus interval needed for accurate two-pulse discrimination has been shown to (i) decrease monotonically with flash duration, luminance, and contrast; and (ii) increase monotonically with the spatial frequency of the target.

A signal-detectability two-alternative forced-choice procedure was employed to reexamine the effects of spatial frequency on temporal resolution. Also assessed was the effect of grating orientation on such performance. The results confirm that temporal resolution declines with increases in spatial frequency. Furthermore, temporal resolution was significantly lower when oblique, as opposed to vertical, grating targets were used. This ‘oblique effect’ in temporal resolution was observed only with the highest-spatial-frequency target (15 cycles deg−1), and not with stimuli of lower spatial frequency (0·9 and 3·8 cycles deg−1). These findings suggest that stimulus parameters which elicit greater transient channel activity, as opposed to sustained channel activity, enhance temporal resolution. When transient activity is at a minimum, meridional differences in temporal resolution are likely to be attributable to sustained channel activity.
Further Remarks concerning Visual Images Observed following Unilateral Enucleation
Authors: Gillmor C Stewart
Published: January 2007

Following an earlier report, the article offers additional points concerning visual images observed after enucleation. These concern: (i) the relationship between field-cut due to the lesion before surgery and corresponding blank areas within the post-enucleation images; (ii) similarities in motion between the foveal images and foveally-fixated afterimages; (iii) possible correspondence of time course of the images to transneuronal atrophy and cell loss in human and monkey studies.
Size Discrimination with Low Spatial Frequencies
Authors: Smith Robert A
Published: January 2007

The hypothesis that visual size is determined from the low-frequency Fourier spectrum of the image has been tested in a variety of ways. The fact that size discrimination of vertical bars is unimpaired when high spatial frequencies are filtered out of the image by blurring, and the fact that spatial-frequency adaptation alters perceived size, argue in favor of such hypothesis. However, the hypothesis is weakened by the observation that discrimination is also unimpaired by filtering low frequencies out of the image and by the observation that some manipulations which alter the Fourier transform produce no corresponding perceptual change. No current theory of size perception appears to fit all of these data.
The Creation and Reversal of the Müller-Lyer Illusion through Attentional Manipulation
Authors: Coren Stanley , Porac Clare
Published: January 2007

A configuration is presented in which both the overestimated and the underestimated portions of the Müller-Lyer illusion are embedded. In free viewing no distortion of length occurs; however, overestimation or underestimation illusions can be produced by simple manipulation of the attentional set, thus demonstrating one cognitive component in the formation of the Müller-Lyer distortion.
Occluding Edges in Apparent Reversal of Convexity and Concavity
Authors: Howard Ian P
Published: January 2007

Certain undulating surfaces have an ambiguous relief which may appear as convex or concave. The direction of relief is generally held to depend primarily on assumptions about the direction of illumination. It is suggested that this does not apply to pictures with relief features with occluding edges.
Stereoscopic Matching, Eye Position, and Absolute Depth
Authors: Prazdny K
Published: January 2007

The viewing system parameters (in particular the mutual orientation of the coordinate frames fixed respectively to the left and right projection surface) probably have to be explicitly incorporated into solutions to the stereoscopic-matching problem in binocular vision. An algorithm for computing the relative orientation of the two directions of gaze from purely visual information without a prior solution to the correspondence problem is outlined. The availability of an algorithm of this sort seems to be a precondition for any stereoscopic-matching process that uses the epipolar constraint. It is further argued that fixation of objects in the near space requires integration of the results of stereoscopic matching over eye movements, and that this requirement puts rather tight restrictions on the possible form of representing the results of stereoscopic processing.
Parafoveal Words are Effective in Both Hemifields: Preattentive Processing of Semantic and Phonological Codes
Authors: Underwood Geoffrey , Rusted Jennifer , Thwaites Sandra
Published: January 2007

What effect may an unattended word have during a single fixation? Attention was selectively directed to a word exposed for 50 ms by the demand to make a rapid lexical decision response, and during the same presentation a second word was displayed approximately 2.3 deg of visual angle away on the same horizontal axis. The second word was backwards and forwards masked by a random-dot display, and was described to subjects as a distractor which was to be ignored. Although no response was required to this word, it was found to influence response latency to the attended word according to the semantic relationship which existed between the two. They interfered with the lexical decision response when the two words were related in meaning and also when they sounded as if they were related in meaning. These effects argue for automatic processing of the meaning of printed words presented in either visual hemifield, and for their automatic phonological activation.
Factors Influencing the Apparent Rotation of a Line on Radially Transformed Backgrounds
Authors: Wade Nicholas J , Swanston Michael T , Ono Hiroshi , Wenderoth Peter M
Published: January 2007

The expansion and contraction of a display consisting of a stationary grating with a superimposed inclined line leads to the apparent rotation of the line. This phenomenon has been investigated in six experiments with the use of a television system with a motorized zoom lens to effect such transformations. The maximum apparent line rotation occurs with the line at 45° to the grating. In experiment 1 a greater magnitude of apparent rotation was found with a vertical grating and an oblique line than vice versa. Zoom-out (contraction) also produced greater rotation than zoom-in (expansion). The orientation anisotropy was not dependent upon the orientation of the display to the retinal meridian (experiment 2): the extent of apparent line rotation was approximately the same with a vertical grating when the head was upright or tilted so that the retinal meridian was at 45°. At a constant rate of zooming, a zoom duration of 2 s produced a larger apparent line rotation than one of 1 s, but it was not influenced by the initial angular subtense of the superimposed line (experiment 3). Neither the spatial frequency of the grating nor the width of the line affected the apparent rotation (experiments 4, 5, and 6). Experiment 5 compared the apparent rotation when the display was zoomed (i) with a fixed surround and (ii) with a surround that also expanded during zooming. The magnitude of rotation in the latter condition was reduced to about 25% of that with a fixed surround. The results are discussed in terms of the discrepancy between the perceived transformations of the background grating and the superimposed line.
The Effects of Illumination Level and Retinal Size on the Depth Stratification of Subjective Contour Figures
Authors: Bradley Drake R , Dumais Susan T
Published: January 2007

The apparent stratification in depth of subjective contour figures over their backgrounds was investigated as a function of illumination level, figure size, and viewing distance. Magnitude estimation, with a real contour figure serving as the modulus, was used to measure the stratification in depth of a subjective contour figure over its background. Illumination level and retinal size both had significant effects on the depth stratification of the subjective contour figures. The greatest apparent depth differences were obtained for figures of small retinal size under low levels of illumination. These results paralleled previous findings for judgments of subjective contour strength. Consequently, both contour clarity and depth stratification of subjective contour figures are affected in similar ways by illumination level, figure size, and viewing distance. The implications of this response coupling are discussed in terms of current theories of subjective contours.
Disappearance of Afterimages at ‘Impossible’ Locations in Space
Authors: Hayhoe Mary M , Williams David R
Published: January 2007

An eccentrically positioned afterimage, viewed in the dark, will disappear if the eye is positioned so that the afterimage now projects to a more extreme location relative to straight ahead. It was found that the afterimage disappeared when it projected to a location which corresponded to the edge of the visual field defined by the brow, cheek, and nose. This suggests that visibility of stimuli from those retinal regions shadowed by the head is influenced by eye-position information.
Extending the Perception of Shape from Known to Unknown Shading
Authors: Berbaum Kevin , Bever Todd , Chung Chan Sup
Published: January 2007

Two experiments are reported which demonstrate the effects of light-source position as an intervening variable upon the perception of relief in pictures. In the first experiment, it is shown that the pattern of light (attached shadow) falling upon forms that can be recognized as having unambiguous surface relief (concave and convex parts) influences the perception of forms with ambiguous surface relief. In the second experiment it is demonstrated that cast shadows may also determine the interpretation of ambiguous relief. These findings suggest that light-source position, implicitly or explicitly, mediates the interpretation of surface relief in pictures.
Flicker Masking of Spatial-Frequency-Dependent Visible Persistence and Specific Reading Disability
Authors: Slaghuis Walter L , Lovegrove William
Published: January 2007

The effect of 6 Hz uniform-field flicker masking of visible persistence at a range of spatial frequencies was investigated in 12-year-old children with specific reading disabilities and a control group of average readers. This reduced differences in visible persistence between the two groups. The results suggest that children with specific reading disabilities experience a deficit in their transient system.
Effects of Luminance and Contrast on Direction of Ambiguous Apparent Motion
Authors: Anstis Stuart M , Mather George
Published: January 2007

A study is reported of the role of luminance and contrast in resolving ambiguous apparent motion (AM). Different results were obtained for the short-range (SR) and the long-range (LR) motion-detecting processes. For short-range jumps (7.5 min arc), the direction of ambiguous AM depended on brightness polarity, with AM only from white to white and from black to black. But for larger jumps, or when an interstimulus interval (ISI) was introduced, AM was less dependent on polarity, with white often jumping to black and black jumping to white.

Two potential AMs were pitted against each other, one carried by a light stimulus and the other by a dark stimulus. The stimulus whose luminance differed most from the uniform surround captured the AM. Visual response to luminance was linear, not logarithmic. When the stimulus was modified to give continuous AM in one direction it was followed by a negative aftereffect of motion only when the spatial displacement was 1 min arc. A larger displacement (10 min arc) gave good AM but no motion aftereffect. Thus only short-range motion adapts motion-sensitive channels.
Temporal Properties of the Short-Range Process in Apparent Motion
Authors: Baker Curtis L , Braddick Oliver J
Published: January 2007

A study is reported of the perception of random-dot two-frame apparent motion in which the durations of each exposure and the interstimulus interval between them were varied. The results are largely consistent with the rule that, for optimal motion detection, a portion of each exposure must fall within the same time interval of about 40 ms. In addition, motion perception is separably dependent on the displacement from one exposure to the next and on the time interval between those exposures, rather than on the ‘velocity implied by their ratio.
Orientational versus Horizontal Disparity in the Stereoscopic Appreciation of Slant
Authors: Ninio Jacques
Published: January 2007

Twenty stereograms with needles either plunging in depth or untilted were constructed. When the geometry of the needles was unbiased, the tilt of the needles was correctly and rapidly appreciated. When the needles were biased so as to remove either their orientational disparity, or the difference in horizontal disparities at the tips, they could be seen, depending on the subject and the nature of the bias, either with or without slant. Orientational disparity proved to be, with two different testing methods, clearly more effective than horizontal disparity in conveying the information of slant. Biased needles at −45° were more often rejected as untilted than biased needles at +45°. The orientational disparity information was ineffective with crosses that combined +45° and −45° needles. The reaction time and the nature of the percept were correlated, the tilted percept taking longer to mature than the untilted one in biased stereograms. Of the seventy tested subjects, one appeared to make no use at all of horizontal disparity in the stereoscopic appreciation of slant.
Influences of Familiarity on the Processing of Faces
Authors: Bruce Vicki
Published: January 2007

Three experiments are reported in which undergraduate subjects made simple perceptual judgements about the faces of familiar and unfamiliar academic staff. Any effects of familiarity in these tasks were assessed by comparison with performance on the two groups of faces when both sets were unfamiliar to student subjects at a different university. In experiment 1 there was no effect of familiarity of the faces on a task requiring judgements of expression, consistent with recent models of face processing in which expression analysis proceeds independently from the analysis of identity. In experiment 2 there was a significant effect of familiarity on a task in which the sex of the faces was judged. This appeared to be due to familiarity acting to facilitate only those faces whose sex was difficult to judge from the picture presented. In experiment 3, significant effects of familiarity were also observed when the task was to distinguish intact faces from jumbled faces. Although the effects of familiarity in experiments 2 and 3 were small and emerged in interactions between item sets and university, they suggest that a simple perceptual hierarchy of the kind proposed by Ellis requires some revision.
Aftereffects in Binocular Rivalry
Authors: Wade Nicholas J , De Weert Charles M M
Published: January 2007

Five experiments are reported in which the aftereffect paradigm was applied to binocular rivalry. In the first three experiments rivalry was between a vertical grating presented to the left eye and a horizontal grating presented to the right eye. In the fourth experiment the rivalry stimuli consisted of a rotating sectored disc presented to the left eye and a static concentric circular pattern presented to the right. In experiment 5 rivalry was between static radiating and circular patterns. The predominance durations were systematically influenced by direct (same eye) and indirect (interocular) adaptation in a manner similar to that seen for spatial aftereffects. Binocular adaptation produced an aftereffect that was significantly smaller than the direct aftereffect, but not significantly different from the indirect one. A model is developed to account for the results; it involves two levels of binocular interaction in addition to monocular channels. It is suggested that the site of spatial aftereffects is the same as that for binocular rivalry, rather than sequentially prior.
The Colour-Matching Functions and Visual Research
Authors: Wright W David
Published: January 2007

The following points are examined: (a) the problem of how to define the colour of a stimulus used in visual research; (b) the limited relation of the colour-matching functions to the spectral sensitivity curves of the individual colour receptors in the retina; and (c) the case for abandoning luminance as a colorimetric variable and lightness as a colour appearance variable.
Interindividual Receptor Variability of Normal Colour Observers: Analysis of the 2-Deg Stiles and Burch Data
Authors: Estévez Oscar
Published: January 2007

Examination of the interobserver variability among the ten observers of the 2-deg Stiles and Burch colorimetric study reveals an interesting pattern: the chromaticities of the matches made by different normal subjects fall approximately on straight lines and these lines appear to converge. Because of a geometric relationship that holds between the normal, anomalous, and dichromatic colour spaces, it can be argued that part of the variability must be due to actual differences in the shape or spectral position of the receptor sensitivities of different normal observers.
The Equivalent Background of Bleaching
Authors: Rushton William A H , MacLeod Donald I A
Published: January 2007

Stiles and Crawford proposed that a retinal region bleached by preexposure to intense light behaves as if it were illuminated by some steady veiling or background luminance. We test this notion by comparing the afterimage of a bleaching light with a steady (and retinally stabilized) light of adjustable intensity, in the manner of Barlow and Sparrock. With their matching procedure, and also with a new procedure, we find as they did that during the rod phase of recovery the afterimage does look like a stabilized field of an intensity which, presented as a background, brings visual sensitivity to the same level. It is as if the two conditions produce equal signals at some stage of the visual pathway. Liked Barlow and Sparrock we observe a rod-cone break in the afterimage matches. However, we argue that the appearance of the rod—cone break presents a paradox and we show a way to resolve it.
The Stiles Summation Index Applied to Heterochromatic Brightness Matching
Authors: Ikeda Mitsuo , Nakano Yasuhisa
Published: January 2007

The summation index technique introduced by Stiles has been applied to heterochromatic brightness matching in order to explain individual differences in luminous efficiency functions for brightness. Such functions were obtained for 2-deg and 10-deg fields from twelve subjects, and the difference between the two fields was compared with the macular pigment density tabulated in Wyszecki and Stiles's book. A summation index was obtained for red and green stimuli combinations and the results are expressed in the form of an equation with nonlinear coefficients. The same equation is applied to the brightness luminous efficiency functions and the individual differences in the efficiency function are interpreted as the result of different contributions of opponent chromatic channels to the perception of brightness.
Perceived Path of Oblique Motion: Horizontal-Vertical and Stimulus-Orientation Effects
Authors: Post Robert B , Chaderjian Marc
Published: January 2007

Subjects adjusted the path of moving stimuli to produce apparent slopes of 45° with respect to horizontal. The stimulus was either a single moving dot or a vertical or horizontal bar. In separate experiments either the stimuli were tracked or fixation was maintained on a stationary fixation target positioned 8 deg to the right of the center of stimulus motion. In both experiments the selected path slopes were in general more horizontal than 45°. This pattern indicates that subjects overestimate the vertical component of motion along an oblique path, and is interpreted as a manifestation of the spatial anisometropy generally termed the ‘horizontal-vertical illusion’. Additionally, paths selected for horizontal bars were more vertical than those for vertical bars. This finding is interpreted in the context of a previous report of the influence of stimulus orientation on perceived velocity.
Relative Effectiveness of Three Stimulus Variables for Locating a Moving Sound Source
Authors: Rosenblum Lawrence D , Carello Claudia , Pastore Richard E
Published: January 2007

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was successful in indicating when a (simulated) moving sound source passed an observer. These three variables were put into competition (with each indicating that closest passage occurred at a different time) in an effort to determine their relative importance. It was found that amplitude change dominated interaural temporal differences which, in turn, dominated the Doppler effect stimulus variable. The results are discussed in terms of two interpretations. First, it is possible that subjects based their judgements on the potential discriminability of each stimulus variable. However, because the stimuli used involved easily discriminable changes, subjects may instead have based their judgements on the independence of a stimulus variable from different environmental situation conditions. The dominance ordering obtained supports the second interpretation.
The Effect of Orientation on Visual and Tactual Braille Recognition
Authors: Heller Morton A
Published: January 2007

Five experiments are reported in which subjects matched tangible or visible braille characters against either visual or tangible arrays. In both modalities recognition was impaired when the characters were tilted, but visual performance was superior to that for touch. Touch may be more sensitive than vision to tilt, since very small deviations from the upright decreased recognition accuracy. Orientation influenced pattern recognition with and without prior information about orientation. Tilting patterns slowed down recognition for tactual–visual matching, but only when orientation was studied with repeated measures. The results are consistent with the hypothesis that it is difficult to code braille patterns tactually as global outline shapes.
Retinal and Extraretinal Information in Movement Perception: How to Invert the Filehne Illusion
Authors: Wertheim Alexander H
Published: January 2007

During a pursuit eye movement made in darkness across a small stationary stimulus, the stimulus is perceived as moving in the opposite direction to the eyes. This so-called Filehne illusion is usually explained by assuming that during pursuit eye movements the extraretinal signal (which informs the visual system about eye velocity so that retinal image motion can be interpreted) falls short. A study is reported in which the concept of an extraretinal signal is replaced by the concept of a reference signal, which serves to inform the visual system about the velocity of the retinae in space. Reference signals are evoked in response to eye movements, but also in response to any stimulation that may yield a sensation of self-motion, because during self-motion the retinae also move in space. Optokinetic stimulation should therefore affect reference signal size. To test this prediction the Filehne illusion was investigated with stimuli of different optokinetic potentials. As predicted, with briefly presented stimuli (no optokinetic potential) the usual illusion always occurred. With longer stimulus presentation times the magnitude of the illusion was reduced when the spatial frequency of the stimulus was reduced (increased optokinetic potential). At very low spatial frequencies (strongest optokinetic potential) the illusion was inverted. The significance of the conclusion, that reference signal size increases with increasing optokinetic stimulus potential, is discussed. It appears to explain many visual illusions, such as the movement aftereffect and center–surround induced motion, and it may bridge the gap between direct Gibsonian and indirect inferential theories of motion perception.
Effects of Orientation-Selective Adaptation on the Zöllner Illusion
Authors: Morikawa Kazunori
Published: January 2007

The model of inhibitory interaction between orientation detectors was examined by prolonged presentation of grating patterns (which was expected to induce orientation-selective adaptation) before measurement of the Zöllner illusion. Adaptation effects were measured under conditions which excluded intrusion by the tilt aftereffect. In experiment 1, illusion magnitude greatly decreased only when the orientation of the adapting grating was the same as that of the inducing lines, which confirmed the first prediction deduced from the model. There was no effect of adapting grating when it was oriented more than 20 ° away from the inducing lines. In experiment 2, adaptation effects were selective not only to orientation but also to spatial frequency. In experiment 3 it was shown that illusion reduction was mediated neither by lowered apparent contrast of the inducing lines nor by retinal adaptation. The results are discussed with respect to the nature of adaptation and possible physiological correlates.
Effect of Stationary Objects on Illusory Forward Self-Motion Induced by a Looming Display
Authors: Ohmi Masao , Howard Ian P
Published: January 2007

It has previously been shown that when a moving and a stationary display are superimposed, illusory self-rotation (circular vection) is induced only when the moving display appears as the background. Three experiments are reported on the extent to which illusory forward self-motion (forward vection) induced by a looming display is inhibited by a superimposed stationary display as a function of the size and location of the stationary display and of the depth between the stationary and looming displays. Results showed that forward vection was controlled by the display that was perceived as the background, and background stationary displays suppressed forward vection by about the same amount whatever their size and eccentricity. Also, the perception of foreground — background properties of competing displays determined which controlled forward vection, and this control was not tied to specific depth cues. The inhibitory effect of a stationary background on forward vection was, however, weaker than that found with circular vection. This difference makes sense because, for forward body motion, the image of a distant scene is virtually stationary whereas, when the body rotates, it is not.
Age-Related Changes in Contrast Sensitivity in Central and Peripheral Retina
Authors: Crassini Boris , Brown Brian , Bowman Ken
Published: January 2007

Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg−1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg−1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg−1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a ‘fuzzy’ edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks. However, consideration must be given to the influence of the nature of the psychophysical task required of observers when making such predictions.
Are Illusory Contours a Cause or a Consequence of Apparent Differences in Brightness and Depth in the Kanizsa Square?
Authors: Watanabe Takeo , Oyama Tadasu
Published: January 2007

The causal flows between the processes responsible for illusory contour clarity, brightness, and apparent depth in the Kanizsa square were examined. The sixty-four stimuli used consisted of all possible combinations of eight disk luminances and eight centre-to-centre separations between nearest disks. Ten subjects were instructed to rate the clarity of the illusory contour and the brightness and apparent depth differences between the Kanizsa square and its surround in each stimulus. On the basis of results obtained with the causal inference method, using partial correlations and path analysis, it is suggested that clarity of illusory contour can be influenced directly by disk separation, and that the output from the process responsible for illusory contour clarity has some effect on the processes responsible for the apparent depth and brightness differences.
Tactile Recognition of Mirror Images by Children: Intermanual Transfer and Rotation of the Palm
Authors: Heath Barbara , Ettlinger George , Brown Josephine V
Published: January 2007

In order to evaluate the importance of the axis of stimulus presentation, inter- and intramanual recognition of mirror pairs was studied with the stimulus materials aligned along the front/back axis (whereas in previous work the mirror pairs were aligned along the left/right axis). Children were allowed to feel shapes with the whole hand, with only four fingers (excluding the thumb), or with only the index finger. After learning with one hand, recognition was tested in experiment 1 with the other hand; after learning with one orientation of the hand (palm down or up), recognition was tested in experiment 2 with the other orientation (palm up or down) of the same hand; after learning with one coronal alignment of the hand (to the left or right), recognition was tested in experiment 3 with the other alignment (to the right or left), but without rotation, of the same hand. Significantly fewer intermanual recognition errors were made on mirror pairs with the materials oriented along the front/back axis than in previous work when oriented along the left/right axis. This supports the suggestion that such errors arise when the stimuli are oriented along the left/right axis during formation of the memory trace. The same trend was unexpectedly obtained for intramanual recognition errors (after rotation of the hand). These errors (after hand rotation) are largely due to coding with respect to the hand; they are reduced when the hand is not aligned with the body axis, since then coding can also occur in relation to the environment.