Processes of overall similarity sorting in free classification.

The processes of overall similarity sorting were investigated in 5 free classification experiments. Experiments 1 and 2 demonstrated that increasing time pressure can reduce the likelihood of overall similarity categorization. Experiment 3 showed that a concurrent load also reduced overall similarity sorting. These findings suggest that overall similarity sorting can be a time-consuming analytic process. Such results appear contrary to the idea that overall similarity is a nonanalytic process (e.g., T. B. Ward, 1983) but are in line with F. N. Milton and A. J. Wills's (2004) dimensional summation hypothesis and with the stochastic sampling assumptions of the extended generalized context model (K. Lamberts, 2000). Experiments 4 and 5 demonstrated that the relationship between stimulus presentation time and overall similarity sorting is nonmonotonic, and the shape of the function is consistent with the idea that the three aforementioned processes operate over different parts of the time course. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overall similarity in adults' classification: The child in all of us.

Six experiments, with 108 undergraduates, tested the hypothesis that adults have direct, nonderived access to overall similarity in the classification of separable stimuli (size and brightness). In 2 experiments, high-speed classification by a similarity rule was either as equally accurate as or more accurate than classification by a dimensional rule, and similarity classification was consistently less affected by accelerating performance. Results suggest that adults' access to overall similarity relations of separable stimuli is not based on recombination of dimensional information. Four experiments tested the hypothesis that adults spontaneously use similarity relations when normal classification is disrupted. Spontaneous classifications under conditions of speed, with a concurrent task load, and with an instruction for impressionistic reponding, elicited overall similarity classifications. In a 2nd classification task, however, speed did not increase overall similarity responding. Results suggest an asymmetry of the integrality–separability distinction. Separable dimensions apparently offer 2 easily available classification modes, but integral dimensions offer only one. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parts, cavities, and object representation in infancy.

Part representation is not only critical to object perception but also plays a key role in a number of basic visual cognition functions, such as figure-ground segregation, allocation of attention, and memory for shapes. Yet, virtually nothing is known about the development of part representation. If parts are fundamental components of object shape representation early in life, then the infant visual system should give priority to parts over other aspects of objects. We tested this hypothesis by examining whether part shapes are more salient than cavity shapes to infants. Five-month-olds were habituated to a stimulus that contained a part and a cavity. In a subsequent novelty preference test, 5-month-olds exhibited a preference for the cavity shape, indicating that part shapes were more salient than cavity shapes during habituation. The differential processing of part versus cavity contours in infancy is consistent with theory and empirical findings in the literature on adult figure-ground perception and indicates that basic aspects of part-based object processing are evident early in life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perception of number from the separability of the stimulus: the Stroop effect revisited

The literature on numerical perception is reviewed from the standpoint of research on selective attention, and predictions are made concerning the dimensional interaction between physical and numerical size of numerals. We manipulated stimulus differences to make the classification of numerical value slightly better (Experiment 1), substantially better (Experiment 2), or worse (Experiments 3-4) than classification of physical size. Garner, Stroop, and redundancy effects were used to gauge the degree of interactive processing. For nearly matched discriminability, both number and size appeared separable when the dimensions were varied orthogonally, but showed Stroop interference and redundancy gain when the dimensions were varied in a correlative fashion. When mismatched, asymmetric Garner and Stroop effects emerged in orthogonal contexts along with Stroop and redundancy gains in correlative contexts. These findings define a unique relation: Numerical value and physical size were optionally separable dimensions. We conclude that a magnitude representation is not mandatory for the perception of numerals. Our conclusions offer a new perspective for understanding both numerical perception and the Stroop phenomenon itself.     

A shape-contrast effect for briefly presented stimuli

When a suprathreshold visual stimulus is flashed for 60-300 ms and masked, though it is no longer visibly degraded, the perceived shape is vulnerable to distortion effects, especially when a 2nd shape is present. Specifically, when preceded by a flashed line, a briefly flashed circle appears to be an ellipse elongated perpendicular to the line. Given an appropriate stimulus onset asynchrony, this distortion is perceived when the 2 stimuli (approximately 4 degrees) are presented as far as 12 degrees apart but is not due to perception of apparent motion between the 2 stimuli. Additional pairs of shapes defined by taper and overall curvature also revealed similar nonlocal shape distortion effects. The test shapes always appeared to be more dissimilar to the priming shapes, a distortion termed a shape-contrast effect. Its properties are consistent with the response characteristics of the shape-tuned neurons in the inferotemporal cortex and may reveal the underlying dimensions of early shape encoding.     

Shape from shading: estimation of reflectance map

The reflectance map used by the visual system for perception of shape from shading was estimated. In Experiment 1, an image of a cylinder or a sphere illuminated from the viewer's direction was presented, and subjects estimated the cross-section of perceived 3D-shape. The reflectance map was estimated from the relationship between the stimulus image intensities and the slants of the measured cross-section. The estimated reflectance maps were not the ones based on Lambertian reflectance properties. In Experiment 2, whether perceived shapes could be predicted based on the reflectance maps obtained in Experiment 1 was examined. Subjects performed the same shape estimation task with images of cylinders generated by the reflectance map obtained in Experiment 1. The perceived shapes coincided well with the shapes used for stimulus image generation. These results indicate that the visual system's estimation of shape from shading can be fully understood based on empirically obtained reflectance maps without mentioning its inaccurate nature which has been claimed by past studies.     

What is the unit of visual attention? Object for selection, but Boolean map for access.

In the past 20 years, numerous theories and findings have suggested that the unit of visual attention is the object. In this study, I first clarify 2 different meanings of unit of visual attention, namely the unit of access in the sense of measurement and the unit of selection in the sense of division. In accordance with this distinction, I argue that an object, as commonly described, is only the unit of selection. The unit of access is better characterized as a Boolean map (Huang & Pashler, 2007), that is, the linkage of a single feature value per dimension associated with a map (i.e., a set of locations). The experiments in this study demonstrated the following: (a) Grouping items into a single object (by connecting them) does not improve the perception of these items (Experiment 1); (b) same-object advantage exists only when the features to be perceived are different dimensions of a single Boolean map and not when they belong to different parts of an object (Experiments 2 and 3); (c) cuing the relevant feature does not help perception when the features to be perceived are different dimensions of a single Boolean map but does help significantly when these features belong to different parts of an object (Experiment 4); and (d) connection, as used in Experiments 1–4, is effective in affecting object structure (i.e., affecting the mechanism of selection) in both an enumeration and a tracking task (Experiments 5 and 6). The results of these experiments, together with data available in the literature, demonstrate that the unit of access is a Boolean map, not an object. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hearing shape.

In 4 experiments, participants listened to suspended occluded objects set into vibration by a pendular hammer. In Experiment 1, participants provided analogue measures of the heights and widths of 3 rectangular steel plates equal in area and weight. The same report method and rectangular dimensions were used in Experiment 2 with 3 plates each of steel, wood, and Plexiglas. Heights and widths were distinguished and perceived in similar proportions to the actual dimensions regardless of material composition. In Experiments 3 and 4, participants successfully identified circular, triangular, and rectangular plates of a single material (Experiment 3) and of 3 different materials (Experiment 4). Discussion focuses on the dependency of perceived dimensions on the physical properties and linear dimensions of the plates and the acoustic structure determined by the solutions to the 2-dimensional wave equation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of color and pattern on implicit and explicit picture memory.

The degree to which repetition priming is perceptually specific is informative about the mechanisms of implicit memory as well as of perceptual processing. In 2 sets of experiments with pictures as stimuli, we tested the effects of color and pattern manipulations between study and test on implicit memory (i.e., naming facilitation) and explicit memory (i.e., 2 forms of recognition). These manipulations did not affect priming. However, participants were able to explicitly detect stimulus changes at above-change levels. changes in color also produced small decrements in participants' ability to judge that repeated stimuli were old on a recognition tests. Experiment 2 showed diminished priming with changes in the stimulus exemplar (i.e., a different picture of the same named object) from study to test, which demonstrated that the picture-naming paradigm is sensitive to changes in physical attributes. The results suggest that physical attributes that are not essential to the formation of a shape representation do not influence repetition priming in a basic identification paradigm. Suggestions for how priming may be mediated are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Category Learning on the Representation of Shape: Dimensions Can Be Biased but Not Differentiated.

Recent studies have suggested a profound influence of category learning on visual perception, resulting in independent processing of previously integral dimensions. The authors reinvestigate this issue for shape dimensions. They first extend previous findings that some shape dimensions (aspect ratio and curvature) are processed in a separable way, whereas others (radial frequency components) are not. They then show that a category-learning phase improved the discrimination of a relevant with respect to an irrelevant dimension, but only for separable dimensions. No similar effect was found on the relative sensitivity for integral shape dimensions. Thus, category learning is capable of biasing separable shape dimensions but does not alter the status of dimensions in the visual system as either separable or integral. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of outline shape in object recognition.

The use of outline shape in recognizing objects was investigated in 4 experiments. In Experiment 1, participants matched a shaded image to either another shaded image or a silhouette. In Experiment 2, they initially named shaded images; later they named either shaded images or silhouettes. Performance in both experiments was predicted by changes in the outline shape of the stimuli. The same matching (Experiment 3) and priming (Experiment 4) paradigms were then used to investigate recognition with objects that were rotated between presentations so as to change the outline shape of the object. Recognition was predicted by changes to outline shape. These results place constraints on models of object recognition and are most compatible with viewpoint-dependent models of recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimensional interaction between color and pitch.

In three experiments I investigated the nature of cross–modal dimensional interaction by testing speeded classification of the synesthetically corresponding dimensions of color (white–black) and pitch (high–low). Experiment 1 showed significant Garner interference when these dimensions were varied orthogonally—redundancy gain for positively correlated dimensions and redundancy loss for negatively correlated dimensions. Attributes from synesthetically congruent stimuli were classified faster than attributes from incongruent stimuli (a congruity effect). Experiment 2 tested a perceptual explanation of this interaction (i.e., that color and pitch are configural dimensions) by using Pomerantz's (1986) diagnostic (comparison of selective and divided attention performance). The configurality hypothesis received little support. Experiment 3 examined the effect of optional processes on color and pitch classification. The results suggest that partly strategic and partly mandatory components may constitute overall performance. Three alternative explanations of the color–pitch interaction—perceptual, semantic, and response based—are evaluated in the context of the present results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Holistic and analytic modes of processing: The multiple determinants of perceptual analysis.

With the use of the criterion of privileged axes, 6 experiments with 96 undergraduates showed that analytic processing of saturation and brightness, prototypical integral dimensions, does sometimes occur. However, it was less frequent and less successful than the analytic processing of separable dimensions. Findings identify several factors that influence whether analytic processing occurs: (a) stimulus factors such as the magnitude of dimensional differences; (b) task factors, including the degree to which analytic processing is encouraged by instructions or by implicit task demands and the amount of time available for processing; and (c) S factors, particularly the amount of experience that the perceiver has had with the stimuli in tasks that encourage stimulus analysis. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What Do Rats Learn About the Geometry of Object Arrays? Tests With Exploratory Behavior.

Six experiments using habituation of exploratory behavior tested whether disoriented rats foraging in a large arena encode the shapes of arrays of objects. Rats did not respond to changes in position of a single object, but they responded to a change in object color and to a change in position of 1 object in a square array, as in previous research (e.g., C. Thinus-Blanc et al., 1987). Rats also responded to an expansion of a square array, suggesting that they encoded sets of interobject distances rather than overall shape. In Experiments 4-6, rats did not respond to changes in sense of a triangular array that maintained interobject distances and angles. Shapes of object arrays are encoded differently from shapes of enclosures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Simon Effect With Stationary Moving Stimuli.

To clarify whether motion information per se has a separable influence on action control, the authors investigated whether irrelevant direction of motion of stimuli whose overall position was constant over time would affect manual left-right responses (i.e., reveal a motion-based Simon effect). In Experiments 1 and 2, significant Simon effects were obtained for sine-wave gratings moving in a stationary Gaussian window. In Experiment 3, a direction-based Simon effect with random-dot patterns was replicated, except that the perceived direction of motion was based on the displacement of single elements. Experiments 4 and 5 studied motion-based Simon effects to point-light figures that walked in place--displays requiring high-level analysis of global shape and local motion. Motion-based Simon effects occurred when the displays could be interpreted as an upright human walker, showing that a high-level representation of motion direction mediated the effects. Thus, the present study establishes links between high-level motion perception and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bias toward regular form in mental shape spaces.

The distribution of figural "goodness" in 2 mental shape spaces, the space of triangles and the space of quadrilaterals, was examined. In Experiment 1, participants were asked to rate the typicality of visually presented triangles and quadrilaterals (perceptual task). In Experiment 2, participants were asked to draw triangles and quadrilaterals by hand (production task). The rated typicality of a particular shape and the probability that that shape was generated by participants were each plotted as a function of shape parameters, yielding estimates of the subjective distribution of shape goodness in shape space. Compared with neutral distributions of random shapes in the same shape spaces, these distributions showed a marked bias toward regular forms (equilateral triangles and squares). Such psychologically modal shapes apparently represent ideal forms that maximize the perceptual preference for regularity and symmetry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinguishing types of superficial similarities: Different effects on the access and use of earlier problems.

When solving a problem, people often access and make use of an earlier problem. A common view is that superficial similarities may affect which earlier problem is accessed, but they have little or no effect on how that earlier problem is used. The reported experiments provide evidence against this view. Subjects learned four probability principles illustrated by word problems. Test problems varied in their similarity to the study problems in three ways: story lines, objects, and correspondence of objects' roles (i.e., whether similar objects filled similar roles). The superficial similarity of object correspondences had a large effect on use (Experiment 1), although it sometimes had little or no effect on access (Experiment 2). Experiment 3 showed that two superficial similarities, story lines and object correspondences, differentially affect and use. These results suggest a more complex role of superficial similarity in problem solving and the need for distinguishing types of superficial similarities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localizing the first position of a moving stimulus: the Fr?hlich effect and an attention-shifting explanation

When subjects are asked to determine where a fast-moving stimulus enters a window, they typically do not localize the stimulus at the edge, but at some later position within that window (Fr?hlich effect). We report five experiments that explored this illusion. An attentional account is tested, assuming that the entrance of the stimulus in the window initiates a focus shift toward it. While this shift is under way, the stimulus moves into the window. Because the first phenomenal (i.e., explicitly reportable) representation of the stimulus will not be available before the end of the focus shift, the stimulus is perceived at some later position. In Experiment 1, we established the Fr?hlich effect and showed that it size depends on stimulus parameters such as movement speed and movement direction. In Experiments 2 and 3, we examined the influence of eye movements and tested whether the effect changed when the stimuli were presented within a structural background or when they started from different eccentricities. In Experiments 4 and 5, specific predictions from the attentional model were tested: In Experiment 4 we showed that the processing of the moving stimulus benefits from a preceding peripheral cue indicating the starting position of the subsequent movement, which induces a preliminary focus shift to the position where the moving stimulus would appear. As a consequence the Fr?hlich effect was reduced. Using a detection task in Experiment 5, we showed that feature information about the moving stimulus is lost when it falls into the critical interval of the attention shift. In conclusion, the present attentional account shows that selection mechanisms are not exclusively space based; rather, they can establish a spatial representation that is also used for perceptual judgement--that is, selection mechanisms can be space establishing as well.