Perception

Figure drawings by 30 blind and 30 sighted children, tested under blindfold and visual conditions, were compared on positioning and drawing scores. Results showed that the majority of the blind, unlike the sighted made positioning errors, and were unaware of the correct placement rule. The older blind did not differ from the sighted on figure drawing, but the younger blind scored significantly worse. Blindfolded compared to visual conditions produced decrements mainly on cohesion and amount of detail by the sighted.

The findings suggest that drawing depends on the acquisition of translation rules for which prior visual experience is a facilitating but not a necessary condition. The absence of visual feedback during drawing seems to have detrimental effects mainly on the articulation of drawing.

A training study was conducted with ten-year old children (1) to determine the steps through which children pass in learning to sort paintings by style; (2) to investigate the relationship between this and other perceptual and performing skills. Subjects who initially focused on subject matter cues learned to sort paintings by style; a substantial proportion of the subjects succeeded in consistently applying a multidimensional analysis, by means of which various compositional components were first independently assessed and their cumulative effects then evaluated. Moreover, the subjects passed through a consistent set of stages en route to style sensitivity. Posttesting revealed that sensitivity to style is more likely to be enhanced if subjects have had intensive exposure to a small set of highly distinctive styles than if they have gained a superficial familiarity with a wide variety of styles; that the classification skills leading to style sensitivity are related to certain discriminative capacities utilized in the sciences; and that subjects trained to attend to certain features of painting show a modest change in their own style of representational drawing. The findings are discussed in terms of the cognitive capacities emerging during the middle years of childhood.

Subjects were shown pairs of slides; one member of each pair represented a painting in its correct left-right orientation and the other a mirror image of the same painting. For each pair, subjects were asked (a) to choose which they preferred, (b) to choose which they thought was the original, and (c) to rate their confidence that they had seen the picture before. Subjects were only able to discriminate between originals and mirror images for those paintings they were highly confident of having seen before.

The Songe of Papua New Guinea have little or no indigenous pictorial art. Nevertheless, Songe subjects of both sexes of varying ages and degrees of Western contact were able to identify a wide range of outline drawings depicting objects, animals, and human forms. ‘Kinetic’ scenes and outline drawings portraying colour and texture discontinuities presented some difficulty for the Songe, especially for those over forty years old. Informants over forty in general made significantly more errors than those under forty. It was noted that this has been found in research in many other cultures.

Scanning from left to right through arrays of shapes is slower with vertical than with horizontal lines. The reverse is true for scanning from top to bottom. Thus, lines lying across the direction of scan appear to act as barriers.

The physical similarity between the target and the irrelevant items, and the number of irrelevant items, were varied to obtain curves relating accuracy of target location to exposure, and reaction time to exposure. Two groups of subjects searched circular displays where similarity differed for each group, and number and exposure varied within groups. The results indicated that the relationships between accuracy and exposure were the more informative since they directly reflected processing, particularly when the exposure was very brief. These time versus accuracy curves were negatively accelerated, showing rapid increases in accuracy for approximately 50 ms with very slow (if any) increases for longer exposures. As it was not possible to account for these accuracy variations in terms of simple serial or parallel models of information processing, they were seen as reflecting processing by preattention and focal attention. Further analysis suggested that the times required for preattentive processing were brief and have a probability distribution.

Four experiments on rats and squirrel monkeys are reported which show that the well-known transposition by animals to continuous from broken or interrupted line stimuli, first reported by Krechevsky, is attributable to their failure to transfer from simultaneous to successive discrimination of dot patterns. When given appropriate successive discrimination training, however, monkeys reverse their original preference and select dot instead of continuous line stimuli.

A viewer is assumed to look with one eye at a fixation point f and a reference point x of a surface in a frontal parallel plane. He can move his eye along its line of regard for f some distance ΔS; and we suppose that he can assess the ratio ΔR⁻¹/ΔS, where R is the retinal separation between the images of f and x and ΔR⁻¹ is the change in the reciprocal of R that attends his movement of a distance ΔS. A model is proposed that approximates the optical conditions of his stimulation, and that allows him to calculate the physical distance E between f and x and the distance S between f and the center of his eye in terms of ΔR⁻¹/ΔS. His calculations of E and S are treated as perceptions of the linear extent and the distance of the surface on which the points f and x are located.

Hypnotic anesthesia was used to reduce sensation in the adapting arm during prism displacement. Magnitude of adaptation to displacement was assessed by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS). Hypnotic anesthesia for the entire arm nearly eliminated adaptation as measured both by NA and PS. This was not the case when only portions of the arm (receptor joints) were selectively anesthetized. The sum of NA when different parts of the arm were left unanesthetized at different times equaled such adaptation produced when all those arm locations were left unanesthetized simultaneously. This was also the case for PS. VS, which involved no arm movements, was not affected by hypnotic anesthesia. Support for Wilkinson's component additive model (NA = PS + VS) was found only when the adapting arm was not anesthetized.

It has been shown earlier that visual exposure to a room tilted 22° leads to long-lasting changes in visually guided postexposure judgments of the vertical in the direction of room tilt. Data from the present experiments indicate that visual exposure to the tilted room also alters kinesthetically-guided postexposure judgments of vertical in the same direction. This change occurs in responses made by both hands regardless of whether the hand tested was used to make the judgments during the exposure phase.

The Müller-Lyer illusion was measured in thirty-five female subjects using the equation method. Three figures based on the illusion were used. One (outgoing fins) produced an illusion of expansion, another (ingoing fins) produced an illusion of contraction, and one was a plain line. The plain line was included to control for the error of the standard as a possible ‘contaminating factor’ which may produce asymmetry in the Müller-Lyer illusion. Although the error of the standard was found to correlate with the asymmetry to a statistically reliable degree, it accounted for only 39% of the size of the asymmetry and only 15% of the variance. At least some of the asymmetry is therefore attributable to the error of the standard, but the data indicate that there is another contributing factor (as yet unspecified). The possibility that the Müller-Lyer illusion may be inherently asymmetrical is discussed.

As an extension of an experimental design reported previously the microstructure of dual task interaction was investigated in a condition in which task instructions favoured the task which had previously been designated the secondary task.

In the situation explored in this paper subjects worked on the five-choice serial reaction task (designated secondary task) whilst at the same time they received single auditory digits at random time intervals, performed a transform operation (adding seven), and called the answer out into a voice key.

The nature of the interaction was investigated using fine analysis of data, and it is argued that the results give further support to the view that subjects were processing information sequentially. A change in the patterning of serial responses in the interval defined by the digit stimulus (D_s) and the digit response (D_r) under the changed-instructions condition suggested that individuals are able to play an active role in the ordering of the attention process in sequential processing situations. ‘Process theory’, in which the information processing state of the main task is considered to have a direct influence on the response to the secondary task signal, is argued to be of little use in explaining the data. Two types of explanations based on criterion theory are considered—one which involves criterion setting with respect to a direct time base and one which relies on information processing stage, as an indirect time base.

It is argued that the microstructure of dual task interaction should be investigated more closely and that the ordering of the time-sharing process is a skill.