Area perception in simple geometrical figures

The results of experiments on visual perception of area of circles and squares are reported. Pairs of geometrical figures were presented simultaneously on an oscilloscope screen. While one of them was fixed, the other one was controlled by an experimental subject. The task of the subject was to match the area of the variable figure to the area of the fixed one. The obtained data show underestimation of the area of circle when compared with square. A mathematical model designed to explain this phenomenon is proposed here. The image function defined as a low-pass filtered (blurred) version of the figure is employed for this purpose. Then, instead of the position of the image function maxima, the position of a threshold value is used for area computation.     

Some experiments relating to the perception of complex tones

Pattern recognition models for the perception of complex tones assume that the pitch of a complex tone is derived from more primary sensations, such as the pitches of the individual partials. Thus a complex tone will only have a well-defined pitch when at least one partial in the complex is separately perceptible. Models based on time-interval measurements, on the other hand, require an interaction of the original components, so that the periodicity of the input waveform is preserved. In Experiment I the relative intensity of a “target” tone, necessary for its identification in the presence of either one or two “masking” tones, was determined, over a range of frequencies. This intensity changes abruptly at around 5 kHz, a result consistent with the idea that the pitches of pure tones are determined by temporal mechanisms for frequencies up to 5 kHz, and by place mechanisms for frequencies above this. In Experiments II and III the audibility of the partials in a multi-tone complex was measured as a function of their frequency separation and compared with the range of conditions over which a complex stimulus produced a clear pitch sensation, using the same set of subjects in each experiment. It was found that under some conditions the complex had a well-defined pitch when none of the individual partials was separately audible. This is contrary to the predictions from the pattern recognition models. The effects of masking noise in the frequency region below the complex, and the results of individual subjects, also did not conform with the predictions from these models. Such models are not ruled out, however, for low harmonic numbers, or for stimuli containing only a small number of partials.     

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.     

Context influence on the perception of figures as conditional upon perceptual organization strategies

Two experiments tested the effect of context on figure perception. Subjects were shown rapid sequences of three figures: a prime, a whole, and a part. They were asked to decide if the third figure was a part of the second (Experiment 1) or if the second and third figures were the same or different with respect to a particular angle (Experiment 2). The prime served to establish a context for stimuli that followed to be compared. Priming had influence on the part—whole comparison in Experiment 1, but not on the local comparison in Experiment 2. The results of Experiment 1 were interpreted as evidence for a role of prior information in perceptual organization. Experiment 2 showed that the task must require an integrative perceptual organization strategy for the priming effects to occur.     

Infants' perception of illusory contours in static and moving figures

We investigated 3-8-month-olds' (N=62) perception of illusory contours in a Kanizsa figure by using a preferential looking technique. Previous studies suggest that this ability develops around 8 months of age. However, we hypothesized that even 3-4-month-olds could perceive illusory contours in a moving figure. To check our hypothesis, we created an illusory contour figure in which the illusory square underwent lateral movement. By rotating the elements of this figure, we created non-illusory contour figures. We found that: (1) infants preferred moving illusory contours to non-illusory contours by 3-4 months of age, and (2) only 7-8-month-olds preferred static illusory contours. Our findings demonstrate that motion information promotes infants' perception of illusory contours. Our results parallel those reported in the study of partly occluded objects ().