Size constancy in extended haptic space

When a stick is used to extend the boundaries of the world perceived by touch, haptic parallels to visual angle and size constancy appear. In a pilot study, Ss using a stick to feel an out-of-reach gap were more likely to underestimate its size than were Ss feeling a nearby gap with the index finger, but size constancy was relatively high with the stick. The main study, comparing judgments of gaps at intermediate and far positions, confirmed these findings. Errors were greater for the more distant gap, but constancy was high in both positions. Correlations between far and intermediate judgments indicated that Ss were consistent in the type of error made. Similar findings emerged from a partial replication with blind and partially sighted Ss.     

Size constancy in monkeys with inferotemporal lesions

In a study of size constancy, monkeys were trained with extended practice to choose the larger of two projected stimulus discs independently of distance. When surgical brain lesions were made following pre-operative training, it was found that posterior parietal lesions caused no deficit on this task while inferotemporal lesions caused a severe breakdown from which three out of four animals showed almost no recovery. Mathematical analysis showed that the pattern of performance after inferotemporal lesions could be described as due to a tendency to oscillate between a “correct” and two “incorrect strategies” and that this tendency was also apparent to at least some extent in the unoperated animals. It is argued that the two incorrect strategies might have resulted from a disturbance of size constancy, such that the animal became unable to use both retinal size and distance information in computing physical size and instead used either retinal size or distance information alone. Parallels are drawn between such an hypothetical perceptual disorder and certain clinical disturbances in man.     

Size constancy in children: a new interpretation

Existing evidence indicates that there are differences between children and adults in size constancy when observation distances are large. Findings are reported which suggest that this phenomenon is based on a difference in the accessing of proximal stimulus information, which, in the case of size, refers to visual angle subtended. Age differences were found when a traditional size constancy task was used, but these differences disappeared when all the comparison objects subtended the same visual angle. Since this finding demonstrates that young children can make accurate size matches, it is suggested that the underconstancy previously reported is not necessarily the result of children's inability to use fully certain cues to distance. Rather, the findings suggest that children access proximal stimulus information more spontaneously than do adults.     

Size constancy in infants: 4-month-olds' responses to physical versus retinal image size

This study tested whether 4-month-old infants respond primarily to objects' physical or retinal image sizes. In the study's main experiment, infants were habituated to either a 6-cm-diameter disk at a distance of 18 cm or a 10-cm disk at 50 cm. They were then given 2 test trials in which the 6- and 10-cm disks were presented side by side at a distance of 30 cm. For each infant, one test object had a novel physical size but a familiar retinal image size, and the other had a familiar physical size but a novel retinal image size. The infants exhibited a significant looking preference for the object that had a novel physical size. A preliminary experiment found that 4-month-olds' looking preferences are based on novelty, not familiarity, under the conditions of this study. Given this finding, the results suggest that 4-month-old infants attend and respond primarily to physical size, not to retinal image size.     

Naming versus matching in color constancy.

In this paper, a replication of the color-constancy study of Arend and Reeves (1986) is reported, and an alternative method is presented that can be used for the study of higher order aspects of color constancy, such as memory, familiarity, and perceptual organization. Besides a simultaneous presentation of standard and test illuminants, we also carried out an experiment in which the illuminants were presented successively. The results were similar to Arend and Reeves's; however, in the object-matching condition of the successive experiment, we found an overestimation, instead of an underestimation, of the illuminant component. Because the results of matching experiments are difficult to interpret, mainly due to their sensitivity to instruction effects, we introduced another type of color-constancy task. In this task, subjects simply named the color of a simulated patch. It was found that, by applying such a task, a reliable measure of the degree of identification of object color can be obtained.     

Probability of Stimulus Equivalence as a Function of Class Size vs. Number of Classes

The Psychological Record - Two experiments were conducted to study stimulus equivalence as a function of class size and number of classes. In the first experiment, equivalence was tested in 50...     

Implicit-shape constancy as a factor in pictorial perception.

Schoolboys from the Ivory Coast and from Kenya were tested on a simple task intended to detect the effect of implicit-shape constancy. The presence of such an effect was confirmed. Comparison of two Ivorean subsamples differing in their responses to a request to build a model of a depicted structure showed that those subjects who build flat (2D) models were less influenced by the implicit-shape constancy than those subjects who built three-dimensional structures. This confirms a postulated link between the implicit constancy and perception of pictorial depth.     

Cues to viewing distance for stereoscopic depth constancy.

A veridical estimate of viewing distance is required in order to determine the metric structure of objects from binocular stereopsis. One example of a judgment of metric structure, which we used in our experiment, is the apparently circular cylinder task (E B Johnston, 1991 Vision Research 31 1351-1360). Most studies report underconstancy in this task when the stimulus is defined purely by binocular disparities. We examined the effect of two factors on performance: (i) the richness of the cues to viewing distance (using either a naturalistic setting with many cues to viewing distance or a condition in which the room and the monitors were obscured from view), and (ii) the range of stimulus disparities (cylinder depths) presented during an experimental run. We tested both experienced subjects (who had performed the task many times before under full-cue conditions) and na?ve subjects. Depth constancy was reduced for the na?ve subjects (from 62% to 46%) when the position of the monitors was obscured. Under similar conditions, the experienced subjects showed no reduction in constancy. In a second experiment, using a forced-choice method of constant stimuli, we found that depth constancy was reduced from 64% to 23% in na?ve subjects and from 77% to 55% in experienced subjects when the same set of images was presented at all viewing distances rather than using a set of stimulus disparities proportional to the correct setting. One possible explanation of these results is that, under reduced-cue conditions, the range of disparities presented is used by the visual system as a cue to viewing distance.     

The relation between similarity grouping and perceptual constancy.

In two experiments on whether similarity grouping is based on the retinal or the perceived slopes of lines, observers judged the grouping of diagonal lines when a display of vertical and diagonal lines was presented upright and when it was slanted 75 deg toward the floor. The floorwise slanting of the display improved gouping, as would be expected if the spontaneous organization of a field into groups in strongly influenced by the projection-level representation of stimuli. It is proposed that similarity grouping occurs at the readout stage of stimulus processing and involves segregating a field into groups on the basis of extrafoveal stimulus differences that are responded to in parallel; or if sequentially, very quickly and independently of focal attention.