The use of computer graphics animation in motion perception research

The advantages and limitations of using computer-animated stimuli in studying motion perception are discussed. Most current programs of motion perception research could not be pursued without the use of computer graphics animation. Computer-generated displays afford latitudes of freedom and control that are almost impossible to attain through conventional methods. There are, however, limitations to this presentational medium. At present, computer-generated displays present simplified approximations of the dynamics in natural events. We know very little about how the differences between natural events and computer simulations influence perceptual processing. In practice, we tend to assume that the differences are irrelevant to the questions under study and that findings with computer-generated stimuli will generalize to natural events.     

The display and animation of full-color images in real time on the Macintosh computer

Techniques for displaying and animating full-color and gray-scale images in real time are illustrated with Pascal examples. The Palette Manager procedures included in the Macintosh Toolbox are used to circumvent the speed limitations inherent in drawing and redrawing images on the Macintosh’s video display. With the technique of palette animation, images of arbitrary size and complexity can be displayed easily and animated at the scan rate of the video monitor. The routines described here are based on Toolbox procedures available on any Macintosh with color video capabilities.     

A visual display system for reading and visual perception research

The selection of a computer visual display system suitable for word recognition and reading research is described. The software character generation routines permit flexible definition of character sets. The display software permits control of size scaling and point density of characters being displayed as well as control over the temporal microstructure of presenting and refreshing the displayed text.     

The Macintosh as a user-friendly laboratory for perception and cognition

We present a radically user-friendly Macintosh laboratory, MindLab, for instruction in perception and cognition. MindLab’s forte is its ability to display pictorial stimuli, including digitized photographs, transferred via the clipboard from Macintosh graphics applications. An experiment is programmed by specifying sequences of event primitives, represented by icons, to which stimuli, temporal parameters, and feedback options are assigned.     

The infant's use of visual and haptic information in the perception and recognition of objects

The purpose of this paper is to discuss the relationship between the haptic and visual systems during infant's bimodal interaction with objects. Four general topics are discussed: the role of exploratory activity in perception, the specific ways in which the two systems are related during exploration, developments over age in the relationship between the systems, and the impact of the organism/environment relationship on these developments.     

The visual perception of velocity

Summary In this section it is concluded that velocity is perceived directly and is dynamically conditioned by the structure and general properties of the visual field in which the movement occurs. The visual perception of velocity follows dynamic laws that are not immediately deducible from the velocity of the stimulus as physically defined. No physiological theory is offered but it is pointed out that the theory of physiological Gestalten is essentially correct in its basic assumptions concerning the perception of movement.The investigation has bearing on the problems of movement thresholds, movement after-images and the perception of time.This paper is abridged from a thesis presented to the faculty of the graduate school of Yale University in partial fulfilment of the requirements for the degree of Doctor of Philosophy. The study was started in the Psychological Institute of the University of Berlin in 1926–1927 and completed at Yale University in 1928–1929. The work at Berlin, which has been already reported [cf. J. F. Brown, Über gesehene Geschwindigkeit. Psychol. Forschg 10, 84–101 (1927)] was largely exploratory in nature; that at Yale was undertaken to fill the gaps in the experimental series and to control more completely the causal factors. For clarity of exposition the previously reported data are included here so far as necessary. The writer is indebted to Professor W. Köhler of the University of Berlin for suggesting the problem, and to Professors R. P. Angier, R. Dodge, and L. T. Spencer of Yale University for many valuable suggestions. He wishes also to express his thanks to the subjects who served in the experiments.     

The phenomenological character of color perception

When an object looks red to an observer, the visual experience of the observer has two important features. The experience visually represents the object as having a property—being red. And the experience has a phenomenological character; that is, there is something that it is like to have an experience of seeing an object as red. Let qualia be the properties that give our sensory and perceptual experiences their phenomenological character. This essay takes up two related problem for a nonreductive account of qualia. Some have argued that on such an account there is no room in a physicalist ontology for qualia. Section 1 shows how qualia might fit into a physicalist ontology. The second problem begins with the observation that there is a gap in scientific accounts of color experience; there is no explanation of why the features of the brain that determine our color experiences give those experiences their phenomenological character. Building on the results of Sect. 1, Sect. 2 develops an account of color perception that bridges this gap and shows how qualia give color perception its phenomenological character. To get a grip on the issues involved the paper begins by considering some aspects of a physicalist account of color.     

The perception of color from motion

We introduce and explore a color phenomenon which requires the prior perception of motion to produce a spread of color over a region defined by motion. We call this motion-induced spread of colordynamic color spreading. The perception of dynamic color spreading is yoked to the perception of apparent motion: As the ratings of perceived motion increase, the ratings of color spreading increase. The effect is most pronounced if the region defined by motion is near 1° of visual angle. As the luminance     

The empirical basis of color perception

Rationalizing the perceptual effects of spectral stimuli has been a major challenge in vision science for at least the last 200 years. Here we review evidence that this otherwise puzzling body of phenomenology is generated by an empirical strategy of perception in which the color an observer sees is entirely determined by the probability distribution of the possible sources of the stimulus. The rationale for this strategy in color vision, as in other visual perceptual domains, is the inherent ambiguity of the real-world origins of any spectral stimulus.     

Demonstration experiments in perception and cognitive psychology for the Macintosh computer

A package of programs demonstrating psychology experiments widely cited in perception and cognitive psychology textbooks is described. The programs are suitable for laboratory research projects and in-class demonstrations. An attractive feature of the programs is that they have provisions for changing experimental parameters to allow students to design different experiments from the original programs. Iconic memory, memory scanning (using the additive factors approach), lexical decision, target detection, speeded classification, picture recognition/picture memory, and the Phi phenomenon can be demonstrated.     

The development of separability in visual perception

Under conditions that do not allow focused attention, reports of illusory conjunctions (i.e. errors that wrongly recombine the features of different objects) constitute evidence of the separate registering of features at an early processing level. The occurrence of illusory conjunctions was used to determine whether there is preattentive analysis of component dimensions (colour and form) and of parts of shapes (triangles and arrows) in young children aged 5 to 8 years. Evidence of preattentive analysis was found, even for the youngest children, for colour and form but not for parts of shapes. Although developmental effects hardly reached significance, inspection of abilities assumed to affect the illusory conjunctions phenomenon suggests that at the preattentive stage children can integrate spatially separate segments but lack the capacity to fully analyse connected segments.     

The limits of visual mass perception

The theory of direct perception suggests that observers can accurately judge the mass of a box picked up by a lifter shown in a point-light display. However, accurate perceptual performance may be limited to specific circumstances. The purpose of the present study was to systematically examine the factors that determine perception of mass, including display type, lifting speed, response type, and lifter's strength. In contrast to previous research, a wider range of viewing manipulations of point-light display conditions was investigated. In Experiment 1, we first created a circumstance where observers could accurately judge lifts of five box masses performed by a lifter of average strength. In Experiments 2–5, we manipulated the spatial and temporal aspects of the lift, the judgement type, and lifter's strength, respectively. Results showed that mass judgement gets worse whenever the context deviates from ideal conditions, such as when only the lifted object was shown, when video play speed was changed, or when lifters of different strength performed the same task. In conclusion, observers' perception of kinetic properties is compromised whenever viewing conditions are not ideal.     

The perception of collative properties in visual stimuli

Two experiments were conducted to determine how quickly subjects respond to collative properties (e. g., Complexity, Uncertainty) of visual stimuli. In Experiment 1 subjects were presented with reproductions of paintings and artificial patterns which varied in collative properties (e. g., Uncertainty, Redundancy). Subjects were able to discriminate these properties on related verbal scales after only a single glance (50 msec) as well as after multiple glances (500 and 5000 msec). In Experiment 2 subjects were presented with pairs of paintings and patterns differing along collative dimensions (e. g., High versus Low Uncertainty) in an exploratory choice paradigm. The results show that for exploratory choice subjects were particularly sensitive to unity or order after only a single glance (50 msec) and to diversity or complexity after multiple glances (500 and 5 000 msec). In general, the data for the single glance condition are consistent with theories which attribute holistic processing to the initial phase of perception.     

The visual perception of 3D shape

A fundamental problem for the visual perception of 3D shape is that patterns of optical stimulation are inherently ambiguous. Recent mathematical analyses have shown, however, that these ambiguities can be highly constrained, so that many aspects of 3D structure are uniquely specified even though others might be underdetermined. Empirical results with human observers reveal a similar pattern of performance. Judgments about 3D shape are often systematically distorted relative to the actual structure of an observed scene, but these distortions are typically constrained to a limited class of transformations. These findings suggest that the perceptual representation of 3D shape involves a relatively abstract data structure that is based primarily on qualitative properties that can be reliably determined from visual information.