The visual representation of three-dimensional, rotating objects.

Depth rotations can reveal new object parts and result in poor recognition of "static" objects (Biederman & Gerhardstein, 1993). Recent studies have suggested that multiple object views can be associated through temporal contiguity and similarity (Edelman & Weinshall, 1991; Lawson, Humphreys & Watson, 1994; Wallis, 1996). Motion may also play an important role in object recognition since observers recognize novel views of objects rotating in the picture plane more readily than novel views of statically re-oriented objects (Kourtzi & Shiffrar, 1997). The series of experiments presented here investigated how different views of a depth-rotated object might be linked together even when these views do not share the same parts. The results suggest that depth rotated object views can be linked more readily with motion than with temporal sequence alone to yield priming of novel views of 3D objects that fall in between "known" views. Motion can also enhance path specific view linkage when visible object parts differ across views. Such results suggest that object representations depend on motion processes.     

Attentional demands of processing shape in three-dimensional space: evidence from visual search and precuing paradigms.

The hypothesis that representation of projective shape is preattentive whereas representation of objective shape in three-dimensional space requires allocation of attention was tested in 2 visual search and 2 precuing experiments. In the visual search experiments, the slope for projective shape search was expected to approach 0 and that for objective shape search was expected to be a positive monotonic function of set size. In the precuing experiments, the effects of precuing were expected to be largely limited to the task requiring representation of objective shape. The overall pattern of results conformed to expectations. The findings are interpreted in the context of a model of shape-at-a-slant processing set out by Epstein and Lovitts (1985) and Epstein and Babler (1989, 1990).     

Mental representation of three-dimensional objects in visual problem solving and recognition

Subjects inspected sets of flat, separated orthographic projections of surfaces of potential three-dimensional objects. After solving problems based on these orthographic views, subjects discriminated between isometric views of the same objects and drawings of distractor structures. Recognition of the isometrics, which had never been shown during the problem solving phase of the experiment, was excellent. In addition, recognition of isometrics corresponding to problems that had been solved correctly when presented in orthographic form was significantly superior to recognition of isometrics based on problems solved incorrectly. In Experiment 2, conditions were included in which either orthographic or isometric views functioned as problem solving or recognition displays. Only in the case of orthographic problem solving followed by isometric recognition (Experiment 1) was the superiority of recognition for correctly-solved problems over incorrectly-solved problems obtained. The pattern of results suggests that viewers construct mental representations embodying structural information about integrated, three-dimensional objects when asked to reason about flat, disconnected projections.     

A cross-cultural study of the representation of shape: Sensitivity to generalized cone dimensions

Many of the phenomena underlying shape recognition can be derived from an assumption that the representation of simple parts can be understood in terms of independent dimensions of generalized cones, e.g., whether the axis of a cylinder is straight or curved or whether the sides are parallel or nonparallel. What enables this sensitivity? One explanation is that the representations derive from our immersion in a manufactured world of simple objects, e.g., a cylinder and a funnel, where these dimensions can be readily discerned independent of other stimulus variations. An alternative explanation is that genetic coding and/or early experience with extended contours—a characteristic of all naturally varying visual worlds—would be sufficient to develop the appropriate representations. The Himba, a seminomadic people in a remote region of Northwestern Namibia with little exposure to regular, simple artifacts, were virtually identical to western observers in representing generalized-cone dimensions of simple shapes independently. Thus immersion in a world of simple, manufactured shapes is not required for the development of a representation that specifies these dimensions independently.     

Multidimensional same--different judgments: evidence against independent comparisons of dimensions

Commonly discussed models of performance in the multidimensional same-different task are based on the assumption that independent same-different decisions are reached for each of the stimulus dimensions used in an experiment. In these models, a higher level mechanism examines th outcome of these independent decisions in order to determine whether the stimuli are the same or different overall. Previous evidence indicating that these models are inconsistent with results from same trials is summarized, and a new test of the above assumption using data from different trials is proposed. Detailed analysis of reaction times from different trials is shown, at least for some pairs of dimensions, to be incompatible with the view that separate same-different decisions are reached for each dimension. The major finding is that there are more relatively fast responses in a condition with two dimensions different, compared with the two conditions with only one of the dimensions different, than any processing model treating the dimensions separately could predict. The results suggest that partial information may be combined across dimensions in order to reach a "different" judgment.     

Mental representation in visual/haptic crossmodal memory: evidence from interference effects

Two experiments used visual-, verbal-, and haptic-interference tasks during encoding (Experiment 1) and retrieval (Experiment 2) to examine mental representation of familiar and unfamiliar objects in visual/haptic crossmodal memory. Three competing theories are discussed, which variously suggest that these representations are: (a) visual; (b) dual-code—visual for unfamiliar objects but visual and verbal for familiar objects; or (c) amodal. The results suggest that representations of unfamiliar objects are primarily visual but that crossmodal memory for familiar objects may rely on a network of different representations. The pattern of verbal-interference effects suggests that verbal strategies facilitate encoding of unfamiliar objects regardless of modality, but only haptic recognition regardless of familiarity. The results raise further research questions about all three theoretical approaches.     

Mental representation in visual/haptic crossmodal memory: evidence from interference effects

Two experiments used visual-, verbal-, and haptic-interference tasks during encoding (Experiment 1) and retrieval (Experiment 2) to examine mental representation of familiar and unfamiliar objects in visual/haptic crossmodal memory. Three competing theories are discussed, which variously suggest that these representations are: (a) visual; (b) dual-code—visual for unfamiliar objects but visual and verbal for familiar objects; or (c) amodal. The results suggest that representations of unfamiliar objects are primarily visual but that crossmodal memory for familiar objects may rely on a network of different representations. The pattern of verbal-interference effects suggests that verbal strategies facilitate encoding of unfamiliar objects regardless of modality, but only haptic recognition regardless of familiarity. The results raise further research questions about all three theoretical approaches.     

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.     

Attentional and anatomical considerations for the representation of simple stimuli in visual short-term memory: evidence from human electrophysiology

Observers encoded the spatial arrangement of two or three horizontal line segments relative to a square frame presented for 150 ms either in left or right visual field and either above or below the horizontal midline. The target pattern was selected on the basis of colour (red vs. green) from an equivalent distractor pattern in the opposite left–right visual hemifield. After a retention interval of 450 or 650 ms a test pattern was presented at fixation. The task was to decide whether the test was the same as the encoded pattern or different. Selection of the to-be-memorised pattern produced an N2pc response that was not influenced by the number of line segments nor by the length of the retention interval, but that was smaller in amplitude for patterns presented in the upper visual field compared with patterns presented in the lower visual field. A sustained posterior contralateral negativity (SPCN) followed the N2pc. The SPCN was larger for patterns with three line segments than for two, was larger for patterns encoded from lower visual field than from upper visual field, and returned to baseline sooner for the shorter retention interval than for the longer interval. These results, and others, provide an interesting and complex pattern of similarities and differences between the N2pc and SPCN, consistent with the view that N2pc reflects mechanisms of attentional selection whereas the SPCN reflects maintenance in visual short-term memory.     

Information representation in visual images

How information is represented in visual images was explored in five experiments where subjects judged whether or not various properties were appropriate for given animals. It took more time to evaluate an animal when the subjective image of it was small, whether size was manipulated directly or indirectly (e.g., by having a target animal imaged at the correct relative size next to an elephant or a fly). More time also was required if the animal was imaged in a relatively “complex” environment (next to 4 vs. 2 digits painted on an imaginary wall, or next to a 16 cell vs. 4 cell matrix). Finally, subjectively larger images required more time to evoke than smaller images. These results support a constructivist notion of imagery, and the idea that images may act as ‘analogues’ to percepts.     

A size-congruency effect in memory for visual shape

In five experiments, visual shapes were shown at either a small or a large size for study in the learning phase of a recognition memory experiment. Later, in the test phase, recognition memory was tested in anold-new paradigm in which an equal number of new shapes were mixed at random with previously seen shapes. Half of theold shapes were shown at the same size as in the learning phase, whereas half were shown at the other size. In every experiment, shapes tested at the same size as shown in the learning phase were recognized more quickly and more accurately than shapes tested at a different size. This size-congruency effect was found for line drawings of natural objects and for unfamiliar shapes (i.e., blobs and stick figures). Furthermore, the magnitude of the size-congruency effect depended on the degree of discrepancy between the learning size and the test size. Together, the results suggest that visual shape memory can be sensitive to the size at which patterns are originally encoded, and that the speed and accuracy of recognition memory is influenced by the size of a shape.     

Cross-linguistic evidence for morphological representation in the mental lexicon.

Three types of naturally occurring data address the question of morphological structure in the lexical entry: code-switching, novel forms, and speech errors. The data were collected from a wide variety of languages, including Austro-Polynesian, Semitic, and Altaic languages, and a heretofore untapped set of affixation types, including infixes, circumfixes, multiple affixes, reduplication, and nonconcatenative morphology. The data are used to argue for a dual-listing model of lexical representation (e.g., Pinker, 1991; Frauenfelder & Schreuder, 1992) over full-listing (e.g., Butterworth, 1983) and fully parsed (e.g., Taft & Forster, 1975) models. The paper posits three morphological parameters which are activated language-specifically.     

The representation of visual scenes

The visual world exists all around us, yet this information must be gleaned through a succession of eye fixations in which high visual acuity is limited to the small foveal region of each retina. In spite of these physiological constraints, we experience a richly detailed and continuous visual world. Research on transsaccadic memory, perception, picture memory and imagination of scenes will be reviewed. Converging evidence suggests that the representation of visual scenes is much more schematic and abstract than our immediate experience would indicate. The visual system may have evolved to maximize comprehension of discrete views at the expense of representing unnecessary detail, but through the action of attention it allows the viewer to access detail when the need arises. This capability helps to maintain the 'illusion' of seeing a rich and detailed visual world at every glance.     

Age-related differences in the processing of redundant visual dimensions

Age differences in the redundant-signals effect and coactivation of visual dimensions were investigated in 2 experiments. In Experiment 1 the task required the conjoining of dimensions, whereas in Experiment 2 the spatial separation of dimensions was manipulated. Although coactivation was evident for both age groups when the redundant dimensions occurred at the same location, older adults showed more evidence for coactivation, perhaps because of compensation for declines in perceptual processing. When the redundant dimensions were separated, neither age group showed evidence for coactivation. These findings indicate that the coactive processing of redundant visual dimensions is spared in healthy older adults and that for both groups, attention must be focused on both dimensions for coactivation to occur.     

Systematic angular biases in the representation of visual space

Representing spatial information is one of our most foundational abilities. Yet in the present work we find that even the simplest possible spatial tasks reveal surprising, systematic misrepresentations of space—such as biases wherein objects are perceived and remembered as being nearer to the centers of their surrounding quadrants. We employed both a placement task (in which observers see two differently sized shapes, one of which has a dot in it, and then must place a second dot in the other shape so that their relative locations are equated) and a matching task (in which observers see two dots, each inside a separate shape, and must simply report whether their relative locations are matched). Some of the resulting biases were shape specific. For example, when dots appeared in a triangle during the placement task, the dots placed by observers were biased away from certain parts of the symmetry axes. But other systematic biases were not shape specific, and seemed instead to reflect differences in the grain of resolution for different regions of space. For example, with both a circle and even a shapeless configuration (with only a central landmark) in the matching task, observers were better at discriminating angular differences (when a dot changed positions around the circle, as opposed to inward/outward changes) in cardinal versus oblique sectors. These data reveal a powerful angular spatial bias, and highlight how the resolution of spatial representation differs for different regions and dimensions of space itself.