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PubMed1988

Contrast and assimilation in the Baldwin illusion.

Four experiments were conducted to investigate the role of "large" squares on the occurrence of assimilation and contrast in the Baldwin illusion. In Exps. 1 and 2, in which subjects reproduced the length of the test line, large squares induced illusions of assimilation. In Exp. 3, reproduction of the entire length of the test line also resulted in illusions of assimilation but bisection of the test line and reproduction of one-half the length of the test line resulted in contrast. Exp. 4 replicated the findings involving judgments of one-half the length of the test line. Over-all, the results indicate that judgments of one-half the length of the test line result in contrast, whereas judgments of the entire extent result in assimilation.

Adult↗
PubMed1989

Factor structure of perceptual-motor attributes in normal children: a cross-validation.

The scores on 22 items of the Purdue Perceptual-motor Survey, administered to 567 normal school children of mean IQ 103 and mean age of 116 mo., were subjected to R-factor analysis by the method of principal factoring with orthogonal varimax rotation. The analysis led to the definition of 10 factors: J, ocular control; K, dynamic balance; L, visual-motor fluency; M, chalkboard; N, unilateral-bilateral coordination; O, upper-lower body differentiation; P, form perception; Q, developmental maturation; R, sex; and S, spatial body perception. The results provide cross-validation for previous studies on the perceptual-motor attributes of normal school children.

Child↗
PubMed1997

The "jump" and "release" effects: some observations on the perception of causality.

Two experiments studied the "release" and "jump" effects. Suppose that--on a homogeneous background--a single object moving on a straight trajectory has a constant physical velocity along all its path except in the middle where this velocity is higher or lower for a short time. The release effect occurs when this velocity is lower and the jump effect when it is higher. In the release effect, the object appears to be released from something that held it back. In the jump effect, the object appears to make a jump forward. In line with Premack's 1990 view, these effects suggest a reclassification of causal phenomena in terms of the perceived origin of the change in movement. This origin is perceived as external in Michotte's launching effect and as both internal and external in the release effect and as internal in the jump effect.

Color Perception↗
PubMed1997

Effects of figure context on the apparent length of a line.

This study investigated the effects of figure context on the apparent length of a line. In Exp. 1, ten participants were asked to adjust the length of a comparison line to match a standard line enclosed within a rectangle. The participants consistently overestimated the length of the standard line, demonstrating the stretching effect of figure context on the apparent length of a line. In Exp. 2 (12 participants), the size of the context figure was varied and it had no significant influence on the magnitude of the context effect. In Exp. 3 (nine participants), the context effect was shown not only for squares and rectangles but also for other shapes of figures such as circles and 5-pointed stars. We discuss the possible mechanism of the figure-context effect within Gregory's (1970, 1978) misapplied constancy theory of visual illusions.

Distance Perception↗
PubMed1997

The organization of visual objects: randomness.

A method was described for determining whether or not a pattern of visual objects is arranged randomly. Based on distance to nearest neighbor, it includes three conditions and is designed to avoid Type I errors. Examples were given, and comparisons were made with other methods.

Distance Perception↗
PubMed1998

Synchronization, decrease in strength of pattern, illusory contours, and neon-color effect.

When certain elements in a pattern are replaced by colored lines, a spreading of neon-like color can be seen around the lines. Using a variety of neon displaying patterns, we hypothesize that two conditions are critical to the neon effect. One is the occurrence of illusory contours and another a decrease in strength of pattern of the colored lines. On the basis of the two conditions, various phenomena of the neon effect are discussed. Finally, examining the striking characteristics of the neon effect, the vagueness of the colored lines and the spreading of the color of the colored lines over an illusory area wherein the color stimulus does not exist, we conclude that the neon effect is caused by synchronization of strength of pattern.

Color Perception↗
PubMed1999

Contribution of stimulus attributes to errors in duration and distance judgments--a developmental study.

In Matsuda's 1996 study, 4- to 11-yr.-old children (N = 133) watched two cars running on two parallel tracks on a CRT display and judged whether their durations and distances were equal and, if not, which was larger. In the present paper, the relative contributions of the four critical stimulus attributes (whether temporal starting points, temporal stopping points, spatial starting points, and spatial stopping points were the same or different between two cars) to the production of errors were quantitatively estimated based on the data for rates of errors obtained by Matsuda. The present analyses made it possible not only to understand numerically the findings about qualitative characteristics of the critical attributes described by Matsuda, but also to add more detailed findings about them.

Child↗
PubMed1999

Attention and estimated line length.

Whether attention affects the estimated length of a line has been debated for a long time. Some authors have found estimated length to increase with attention; others have found that it decreased. The present study further investigated this problem with two experiments. The first confirmed that estimated length decreased with attention; however, this result had low reliability. The second experiment indicated that estimated length significantly decreased with attention for some participants and significantly increased for others. This finding accounts for the low reliability of the first experiment and for the conflicting results of previous studies. Implications of opposite effects of attention for models of sensory intensity are discussed. An interpretation of these effects in terms of response preferences is proposed.

Attention↗
PubMed1999

Assimilation and contrast in geometrical illusions: a theoretical analysis.

It is argued that an unwarranted dichotomization of geometrical illusions has produced theories whose explanatory scope is limited to either assimilation or contrast. Since recent attempts at integration lack precision, a 1977 unified model of the perception of extent by Brigner was revised to predict accurately both assimilative and contrastive phases of the parallel lines illusion. Application of the revised model to other geometrical illusions was discussed and a means of parsimoniously accounting for variations in assimilative illusions occurring with age and with lightness of the stimulus figure was suggested.

Age Factors↗
PubMed1999

Shadows as sources of cues for distance of shadow-casting objects.

Shadows are neglected sources of information about shadow-casting objects' distance (location). In an experiment using real shadows, participants judged the distance of two rods, either with shadows (illumination from the left) or without shadows. Without shadows, a thin rod raised slightly above the surface was incorrectly judged to be more distant than a thick rod, but with shadows the thin rod was accurately judged to be closer. For judgments to be correct, shadows had to overwhelm competing height and stimulus-size cues. Exp. II involved nonoverlapping shadows produced by a light placed in front of the rods. Again, without shadows the thin-elevated rod was incorrectly judged to be more distant, but with shadows it was correctly judged to be closer. Exp. III involved two sets of thick and thin elevated rods and frontal lighting. Judgments were accurate when shadows were present but inaccurate when shadows were absent. Experiments conducted through the American Psychological Society Web-research site replicated results of Exp. I, II, and III. A final Web experiment replicated results of the others, but with shadows produced by illumination from the right. Three properties of shadows--angles, interposition, and positioning--are possible sources of distance information associated with cast shadows.

Cues↗
PubMed2000

Angles of shadows as cues for judging the distance of shadow casting objects.

40 participants were presented the six possible comparisons of four pictures of cylinders and their shadows. For each comparison, each participant was to decide which cylinder was most distant from a reference point. Overall 15 of the participants got all six judgments correct, an outcome that is exceedingly unlikely by chance.

Adult↗
PubMed2000

Fundus pigmentation and equiluminant moving phantoms.

Visual phantoms are a perceptual completion illusion wherein contours and surfaces are seen where none physically exist. The visibility of moving phantoms was measured with equiluminant and near equiluminant chromatic inducing gratings for observers having a fundus classified as either darkly or lightly pigmented. Phantom visibility was greatest for observers with a lightly compared to a darkly pigmented fundus with the two groups showing differences in visibility as a function of background luminance. The results are discussed relative to equiluminant stationary phantom findings and a proposed relationship between phantom visibility and magnocellular pathway activity.

Color Perception↗
PubMed2006

Visual search for a circular region perceived as a figure versus as a hole: evidence of the importance of part structure.

To study contour curvature polarity, we compared strictly convex regions (circular figures) with strictly concave regions (circular holes). We tested for an asymmetry between visual searches for concavities and those for convexities. We found that providing a preview of the background benefited search for concavities (holes) more than it did search for convexities (figures) and that for convex figures, nearer targets were responded to more quickly. Importantly, however, we failed to find any support for the hypothesis that concave targets are inherently more salient. We conclude that previous findings in the literature, which have been taken to indicate preferential processing of concavities, due to their increased salience, are more likely the result of an early computation of part structure based on concavities.

Depth Perception↗
PubMed2003

Perceptual representation of visible surfaces.

Two experiments are reported in which we examined the ability of observers to identify landmarks on surfaces from different vantage points. In Experiment 1, observers were asked to mark the local maxima and minima of surface depth, whereas in Experiment 2, they were asked to mark the ridges and valleys on a surface. In both experiments, the marked locations were consistent across different observers and remained reliably stable over different viewing directions. These findings indicate that randomly generated smooth surface patches contain perceptually salient landmarks that have a high degree of viewpoint invariance. Implications of these findings are considered for the recognition of smooth surface patches and for the depiction of such surfaces in line drawings.

Depth Perception↗
PubMed2004

The visual perception of length along intrinsically curved surfaces.

The ability of observers to perceive three-dimensional (3-D) distances or lengths along intrinsically curved surfaces was investigated in three experiments. Three physically curved surfaces were used: convex and/or concave hemispheres (Experiments 1 and 3) and a hyperbolic paraboloid (Experiment 2). The first two experiments employed a visual length-matching task, but in the final experiment the observers estimated the surface lengths motorically by varying the separation between their two index fingers. In general, the observers' judgments of surface length in both tasks (perceptual vs. motoric matching) were very precise but were not necessarily accurate. Large individual differences (overestimation, underestimation, etc.) in the perception of length occurred. There were also significant effects of viewing distance, type of surface, and orientation of the spatial intervals on the observers' judgments of surface length. The individual differences and failures of perceptual constancy that were obtained indicate that there is no single relationship between physical and perceived distances on 3-D surfaces that is consistent across observers.

Depth Perception↗
PubMed2003

The nonindependence of stimulus properties in human category learning.

Typically, models of category learning are verified through behavioral experiments with stimuli consisting of putatively independent dimensions such as shape, size, and color. The assumption of independence is critical in both the design of behavioral experiments and the development of models and theories of learning. Using the standard classification learning paradigm and a common stimulus set, the present work demonstrates that the assumption of independence is unwarranted. Systematic relations span stimulus dimensions and govern learning performance. For example, shape is not independent of size and color, because humans quantify size and color over shape when shape is relevant to the categorization. This quantification is reflected in natural language use (e.g., "blue triangle" as opposed to "triangle and blue"). In this example, color and size are predicates and shape is the argument. Across four experiments, the difficulty of mastering a classification rule can be predicted by the number of predicates that must be unbound in order to free rule-relevant stimulus dimensions.

Color Perception↗
PubMed2003

Independent encoding of colors and shapes from two stimuli.

Observers were presented with brief exposures of pairs of colored objects (letters) and asked to report both the color and the shape of each object. Several observers showed strikingly clear evidence of nearly perfect stochastic independence between reports of the four features (two colors and two shapes). For instance, the probability that the shape of a given object could be reported seemed independent of (a) whether the color of the object could be reported and (b) whether features of the other object could be reported. Such stochastic independence is predicted by many parallel-processing models (e.g., Bundesen, 1990). However, the results are difficult to reconcile with simple serial models in which the encoding of one object is completed before the encoding of another object is begun.

Adult↗