Hans Wallach's research while affiliated with Swarthmore College and other places

Publications (66)

Article
Lines of constant curvature, a circle or a straight line, have no distinguishable parts. Yet they are perceived as if they did. When they move and intersect, they are perceived to slide across each other as if one of them had parts that can be seen to move in relation to the other line. With no such parts present in stimulation, they are products o...
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Full-text available
In the experiment reported, the accuracy of reproductions of the shapes of more or less complex motion paths was used to examine the effectiveness of two stimulation conditions, of ocular pursuit, and of configurational change when the latter took the form of induced motion. Reproductions of the apparent motion paths of an objectively stationary sp...
Article
In a center-surround arrangement of two luminances, luminance ratio, area of the surrounding higher luminances, and separation of the two luminances were varied. Decreasing the area of the surrounding luminance caused the achromatic color in the center to be lighter, and a similar but smaller effect was caused by increasing separation up to approxi...
Article
In the variety of subjective contours that are structured like Kanizsa’s triangle, shapes consist partly of edges of elements that make up the patterns that give rise to the subjective contours and partly of the subjective contours. It was found that familiarity with the shape that fit the subjective-contour-inducing pattern in this fashion increas...
Article
During prolonged monocular observation from afar, an upright wire cube (Necker cube) or a drawing of such a cube inverts continuously so that the lower of the two frontal faces appears to be either in front (version A) or in back (version B). Version A is perceived as if it were viewed obliquely from above and version B as if seen from below. In ou...
Article
The distortion of polar perspective depends on the depth of the tridimensional shape and on the observation distance. In four experiments using 54 undergraduates as subjects, we found that a compensation process which takes depth and observation distance into account corrects for such distortions. Compensation was demonstrated in experiments in whi...
Article
When one looks at a picture from an oblique direction, its retinal projection is foreshortened, but this distortion in proximal stimulation is usually not perceived. A correction akin to shape constancy takes place. Experiments are reported that show that this correction can be the result of compensation that takes the slant of the picture plane re...
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When the eyes are engaged in pursuit movements, the image of a stationary object shifts on the retina, but such a target is either perceived as stationary or seems to move only little. This is the result of a compensation process called position constancy, which takes the eye movements into account. Becklen, Wallach, and Nitzberg (1984) reported th...
Article
Vector theory seems to furnish adequate descriptions of the motions that are perceived in Johansson's 1950displays, motions that are perceived when objects move while the visual field is being displaced relative to the head during the head's turning or nodding, or motions that are perceived when they move where the visual field is expanding during...
Article
Responds to G. Johansson's (see record 1986-10919-001) critique of the present authors and D. Nitzberg's (see record 1986-00251-001) proposed alternative to vector analysis in motion perception. The present authors argue that their use of the 1950 version of vector analysis does not affect the validity of their findings. An example in which vector...
Article
In the perception of distance, depth, and visual motion, a single property is often represented by two or more stimuli. Two instances of such redundant stimulation are discussed: (a) the various stimuli that represent visual motion and (b) the two forms of stimulation by which binocular parallax evokes stereoscopic depth perception. In the case of...
Article
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The nature of a recently reported effect of speed on induced motion was investigated. Wallach and Becklen (1983) had found that the extent of induced motion decreases linearly with increases in presentation speed. We found that this speed effect occurred only in induced motion and not under conditions in which configurational change, which is respo...
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Experiments are reported supporting an altered explanation of the vector analysis that occurs in certain motion displays discovered by Johansson (1950). What seemed the result of a perceptual vector analysis is ascribed to the outcome of two different, independent stimulus conditions to which such displays can give rise because of external vector a...
Article
Five displays with light dots at two or three rim locations on a wheel that rolled inside a hoop of twice the wheel’s diameter were observed. In this arrangement the motion paths of the rim dots are straight and are apparently more readily perceived than the cycloids on which rim dots move when the wheel rolls on a plane. Circular dot motion, the a...
Article
Full-text available
When the eyes track a moving object, the image of a stationary target shifts on the retina colinearly with the eye movement. A compensation process called position constancy prevents this image shift from causing perceived target motion commensurate with the image shift. The target either appears stationary or seems to move in the direction opposit...
Article
Examined position constancy in human vision with 86 college students. When the eyes track a moving object, the image of a stationary target shifts on the retina colinearly with the eye movement. A compensation process called position constancy prevents this image shift from causing perceived target motion commensurate with the image shift. Four exp...
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Reciprocating horizontal motion of a pattern of vertical lines caused horizontal induced motion of a dot that underwent vertical reciprocating motion. The real vertical motion and the induced horizontal motion of the dot resulted in a circular or oval apparent path. Increasing the two motion speeds caused the horizontal component of this resultant...
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A new perceptual adaptation, an alteration in the perceived direction of motion given by ocular pursuit, is reported. When an object starts to move on a straight path, its displacement is initially given by a shift of its image on the retinas of the stationary eyes; then, after about 200 msec, the eyes start to track the moving object. The percepti...
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It is proposed that some distance cues are learned when a perceptual parameter that varies with observation distance is regularly associated with objects whose distances are perceived because another distance cue operates. If that is the way distance cues can come into existence, it may be possible to identify a parameter that varies with distance...
Article
Retinal disparities which produce perceived depth in stereoscopic vision result from configurational differences in the retinal images in the two eyes of objective three-dimensional arrangements. Experiments reported earlier demonstrated special effectiveness of differences in the alignment in the vertical dimensions of the images of points that ar...
Chapter
Two procedures are described with which the relative effectiveness of the three conditions of stimulation that cause motion perception can be explored, and the results of such experiments are reported. Experienced motions are described that result when ocular pursuit and object-relative displacement are stimuli for different components of the motio...
Article
Two arrangements yielding induced motion were used to explore the relative effectiveness of three stimulus conditions known to produce perception of motion—namely, image displacement, ocular pursuit, and object-relative displacement. In these arrangements, object-relative displacement, which resulted in induced motion, was in conflict either with o...
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Full-text available
Prolonged exposure to a reciprocating motion that is tracked by the eyes results in diminished extent of perceived motion. Investigation of this effect showed that it becomes manifest only in perceived motion that is caused by ocular pursuit, but that it is not an eye muscle effect. It may consist in a changed evaluation of eye movements. The resul...
Article
Stereovision is a complex process because perceived depth intervals depend not only on retinal disparity, but also on cues for distance. Because disparity decreases in proportion to the square of the object distance, a compensation process called constancy of stereoscopic depth makes the necessary correction in the perception of depth by taking obj...
Article
Both the image size of a familiar object and linear perspective operate as distance cues in stereoscopic depth constancy. This was shown by separating their effects from the effect of the oculomotor cues by creating cue conflicts between either the familiar size cue or linear perspective, on the one hand, and accommodation and convergence, on the o...
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Full-text available
Retinal disparity decreases in proportion to the square of the distance of the corresponding objective depth interval from the eyes. Up to a distance of 2 m, stereoscopic depth perception compensates well for this decrease in disparity with observation distance; for a given disparity, experienced depth increases approximately in proportion to the s...
Article
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Prolonged exposure to a condition that causes induced motion was found to diminish this effect. The extent of a horizontal induced motion was measured by obtaining estimates of the direction of the apparent oblique path that resulted when a spot was visible on a horizontally moving pattern and was therefore in horizontal induced motion and, at the...
Article
When head-movement parallax functioned as the sole veridical distance cue during exposure to spectacles that altered the eyes’ oculomotor adjustments, sizable adaptation was obtained. This result showed that a discrimination of the distances of 60 and 30 cm can be based on head-movement parallax. Using adaptation in demonstrating that head-movement...
Article
Eye movements were monitored and a target circle subtending an angle of 7o was made to move during and dependent on the eye movements. Thresholds of detection of the resulting abnormal image displacements were obtained. Thresholds were low when both the eyes and the target moved either horizontally or vertically. They were higher by a factor of two...
Article
Ebenholtz and Wolfson have demonstrated an aftereffect of sustained ocular convergence, which they ascribed to eye muscle potentiation. They suggested that this effect can explain an aftereffect of wearing glasses that alter oculomotor cues for distance. Wallach and Frey interpreted this aftereffect as resulting from adaptation. The outcome of two...
Article
Full-text available
Adaptation in the constancy of visual direction can be obtained under two radically different conditions, called eye-movement adaptation and field adaptation. Adaptation resulting from these conditions and from a “normal” condition was measured with a newly developed estimation test. Eye-movement adaptation was found to cause an alteration of compe...
Article
.— The existence of a Pulfrich effect based on ocular convergence was demonstrated by having subjects with a neutral density filter over one eye observe a moving rod in a homogeneous environment. This effect was found to have a smailer magnitude than a Pulfrich effect that was obtained when the rod moved optically in the plane of a dot pattern and...
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Evidence is presented that the perceived immobility of the environment during tilting of the head from side to side results from a compensating process. This compensating process operates well only when peripheral vision is present. An objectively stationary environment was, for instance, not perceived as immobile during head tilting when vision wa...
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The retinal disparities in stereograms where the vertical alignment of pairs of homologous points in one eye differs from that in the other eye were found to be more effective than disparities that do not involve that kind of binocular difference. The presence of such “transverse disparities” was found to shorten the time elapsed until perceived de...
Article
Adaptation in the constancy of visual direction had previously been obtained by causing a large or a small visible area representing the environment to be objectively displaced in dependence on head movements. No stationary objects were permitted to be visible. Now experiments are reported in which displacements of a large patterned field, with the...
Article
Among several shape distortions caused by a wedge prism is one where a pattern of evenly spaced lines that are parallel to the prism base reaches the eye with distances seen through the base region contracted and distances seen through the apex region expanded. Rapid partial adaptation to this distortion was obtained by having subjects who wore the...
Article
When an object increases in size and its retinal image expands, it is perceived to grow. But image expansion caused by one’s approaching an object of constant size does not result in perceived growth of the object. This is due, in part, to correct size perception which takes the distance of the object into account. But perceived growth may have ano...
Article
A new kind of adaptation was discovered, namely, to glasses that cause frontal planes to appear concave. The effect of this adaptation can be observed without the glasses as an apparent convexity of a frontal plane. We measured this effect by bending a frontal plane into a concave surface that compensated for this convexity. To obtain rapid adaptat...
Article
When one moves forward, one views objects to the side of one’s path successively from different directions. In the mover’s visual field, such objects change their orientation; relative to him they undergo a partial rotation. Although this rotation is given in several ways, it is hardly ever perceived. This is due to a compensating process that take...
Article
Counteradaptation, previously demonstrated in connection with adaptation in distance perception, was obtained after exposure to displaced visual direction. When S adapted to a laterally displacing wedge prism by walking during the exposure period, there was not only a change in the perceived visual direction, but also a change m the proprioceptivel...
Article
Adaptation to spectacles that alter in equivalent amounts the accommodation and the convergence with which objects are viewed was produced under two conditions. In one, S alternately pushed away or pulled toward him a screen that exhibited only a single vertical contour while wearing glaaaes that caused decreases in accommodation and convergence eq...
Article
Often adaptation to artificially altered stimulation takes place because veridical stimulation that produces the same perceptual property that is produced by the altered stimulation is also received. In these cases, an assimilation of the two perceptual processes produced by the two different stimulations (the altered and the veridical) is supposed...
Article
Hay and Sawyer recently demonstrated that the constancy of visual direction (CVD) also operates for near targets. A luminous spot in the dark, 40 cm from the eyes, was perceived as stationary when S nodded his head. This implies that CVD takes target distance, as well as head rotation, into account as a stationary environment is perceived during he...
Article
When Ss were simultaneously adapted to horizontal and to vertical target displacements of equal rate during head turning about a vertical axis, the adaptation effects measured by one-trial tests immediately after the adaptation period were about equal. But retests after a time lapse of 10 and 20 min, during which S sat immobile and with eyes closed...
Article
In previous work by the senior authors, brief adaptation to glasses that changed the accommodation and convergence with which objects were seen resulted in large alterations in size perception. Here, two further effects of such adaptation are reported: alterations in stereoscopic depth perception and a change when distance is represented by a respo...
Article
Accommodation and convergence primarily serve to adjust the eyes to the distance of the object viewed, but, once made, these oculomotor adjustments serve as cues for the object’s distance. Experiments are reported that show that the relation between oculomotor adjustments and the distances they signify can be changed by adaptation to glasses that c...
Article
The capacity of accommodation and convergence to serve as cues to distance was assessed. As is usual, size perception was employed as an indicator. The standard technique of obtaining size matches between figures of identical shape yielded poor results. The inadequacy of this technique was revealed when matching the length of two edges that were pa...
Article
When the normal constancy process on which the apparent immobility of the visualfield during head movements is based was strengthened by the same method that produces adaptation to abnormal conditions in the constancy of visual direction, and when this training of the normal constancy process immediately preceded experimental adaptation, the effect...
Article
Adaptation to vertical field displacements dependent on head turning about a vertical axis was demonstrated under two conditions, rapid training with 100 head movements and 1-h-long training with continuous head turning. The effect of rapid training was measured with the slant estimation method. Adaptation after the longer training was ascertained...
Article
Adaptation to field displacement during head movements in the direction with the head rotation and in the direction against it was produced under otherwise identical conditions and compared; the field displacement rate was also varied. A rapid training procedure was used, and a novel one-trial test was employed that could measure the adaptation wel...
Article
Sixty Ss wore vertically displacing wedge prisms and adapted by looking at their feet for 10 min. Half of them did this while standing and the others in supine position. The latter condition produced adaptation measurable with a visual-motor test and with a test of egocentric localization, but on a purely motoric test no adaptation was apparent. St...
Article
Modification of the constancy of visual direction was produced by partially adapting Ss to the displacements of the visual field caused by magnifying lenses during 1 h of continuous head turning. The adaptation effects were measured by determining the range of perceived target immobility before and after this adaptation period. A method for measuri...

Citations

... Previous studies addressing reference frames for motion stimuli mostly focused on processing at the perceptual encoding level. The perceived direction of motion during pursuit has been reported to have retinotopic (Becklen, Wallach, & Nitzberg, 1984;Festinger, Sedgwick, & Holtzman, 1976;Mateeff, 1980;Wallach, Becklen, & Nitzberg, 1985) and incompletely converted spatiotopic coordinates (Souman et al., 2005a(Souman et al., , 2005bSouman et al., 2006aSouman et al., , 2006bSwanston & Wade, 1988). In terms of attentively tracking the identities of multiple moving objects, it has been suggested that both retinotopic and spatiotopic coordinate systems are used (Howe, Pinto, & Horowitz, 2010). ...
... Essentially all demonstrations of occlusion events have concentrated on translatory motions, a condition in which the eyes can easily track a moving figure. Such tracking might constitute a way to obtain information about observer-relative displacements (Wallach, 1982). Alternatively, eye movements could serve as a cue to the motion of a figure that is not fully specified in the luminance domain, as seems to be the case in anorthoscopic perception (Rock, Halper, DiVita, & Wheeler, 1987). ...
... Here the amount of adaptation achieved is measured by obtaining an estimate of the DR equivalent to the perceived motion of the stationary environment. This was done directly by the slant estimation method developed by Wallach and Frey (1969). The indirect method employed in the present work consisted in obtaining an estimate of the extent of the apparent environmental motion produced by a head turning through ajixed angle. ...
... Any aftereffect in Exp. 1 should originate mainly from a change in rest vergence following sustained vergence efforts [19,20]. Any difference in the aftereffects of Exp. 1 and 2 should thus be attributed to a calibration process of the vergence/distance mapping arising from conflicting signals [21,22], here between altered vergence-specified distance and actual reach distance. In the post-tests of both experiments, subjects exhibited a constant distance overestimation across all targets, with a more than twice larger aftereffect in the second one (Fig. 3). ...
... This observation leads to the question of knowing whether it occurs from changes in the vergence tonic state, cue conflict between vergence and other sources of information or, a recalibration of the apparent viewing distance. Wallach and Halperin (1977) found that the hypothesis of tonic vergence changes did not suffice to explain the effect. However, Fisher and Ebenholtz (1986) showed similar effects in the absence of conflict between disparity and monocular cues. ...
... This stationary pattern, in undergoing the normal environmental displacements during head movements, provides training in the field-adaptation component of the ordinary CVD. It has been found on several occasions that training with the ordinary perceptual condition prior to adaptation training will diminish the effect produced by the latter (Epstein, 1971; Wallach & Floor, 1970; Wallach & Karsh, 1963). The same should be true when training with the ordinary perceptual condition is simu:taneous with the adaptation training, as is the case in the eye-movement adaptation condition, which provides eye-movement adaptation training and at the same time strengthens the field-adaptation component of the ordinary CVD. ...
... When presented with the square, subject focused their resources on perceiving the illusion within the square and not on extracting the basic elements that allow the simple discrimination required by the task. Although mechanisms initiated for the induction of illusory contours might occur very early, we know that there are later cognitive modulations changing the saliency of the illusory contours (Bradley & Dumais, 1975; Coren, Porac, & Theodor, 1986; Pritchard & Warm, 1983; Wallach & Slaughter, 1988). These modulations were probably awaited by the subjects before they decided, when presented with a modal square, for the presence or the absence of a square. ...
... Hence, the circular motion of the wheel is perceived with respect to the translatory motion of the bicycle. The inadequacy of using the static environment as the single reference frame and the roles of moving reference frames have been systematically investigated by Johansson (1950Johansson ( , 1958Johansson ( , 1973Johansson ( , 1976Johansson ( , 1986 and many others (Duncker, 1929;Gogel, 1974;Hochberg & Fallon, 1976;Mori, 1979;Wallach, O'Leary, & McMahon, 1982). ...
... Moreover, through the use of random-dot stereograms (which remove all other depth information) Julesz (1971) reported that stereoblindness and stereoweakness not uncommon in the normal population. For our purposes, however, we will suggest that the variability found in stereopsis is unusual for an information source about layout; most other sources seem not show large individual differences nor adaptational differences (but see Wallach & Frey, 1972a, 1972b. ...
... In the context of visualvestibular cross-modal aftereffects, the literature provides early reports of feelings of rotation after being adapted to an optokinetic stimulation, corroborated by the presence of afternystagmus as well [75]. Similarly, MAEs have been observed to be reduced when inertial motion was presented together with visual adaptation [76,77]. After a long hiatus in research, recent investigations of visual-vestibular cross-modal aftereffects pointed towards a more punctual identification of such perceptual phenomena. ...