Results of 4 experiments indicate that both within-modality and case-specific visual priming for words are greater when test stimuli are presented initially to the right cerebral hemisphere (RH). In contrast, neither within-modality nor case-specific explicit memory for words is greater when stimuli are presented initially to the RH. Priming is measured using word-stem completion, and explicit memory is measured using word-stem cued recall. In both cases, Ss first rate how much they like words, and then word stems are presented briefly to the RH (in the left visual field) or to the left hemisphere (in the right visual field). Results suggest that at least 2 separate systems encode the visual representations that produce priming. The system that is more effective in the RH is better at representing form-specific information, whereas another system that is not more effective in the RH does not distinguish among distinct instances of word forms.

Results of 4 sets of neural network simulations support the distinction between categorical and coordinate spatial relations representations: (a) Networks that were split so that different hidden units contributed to each type of judgment performed better than unsplit networks; the reverse was observed when they made 2 coordinate judgments. (b) Both computations were more difficult when finer discriminations were required; this result mirrored findings with human Ss. (c) Networks with large, overlapping "receptive fields" performed the coordinate task better than did networks with small, less overlapping receptive fields, but vice versa for the categorical task; this suggests a possible basis for observed cerebral lateralization of the 2 kinds of processing. (d) The previously observed effect of stimulus contrast on this hemispheric asymmetry could reflect contributions of more neuronal input in high-contrast conditions.

Participants named objects presented in the left or right visual field during a test phase, after viewing centrally presented same-exemplar objects, different-exemplar objects, and words that name objects during an initial encoding phase. In two experiments, repetition priming was exemplar-abstract yet visual when test objects were presented directly to the left cerebral hemisphere, but exemplarspecific when test objects were presented directly to the right cerebral hemisphere, contrary to predictions from single-system theories of object recognition. In two other experiments, stimulus degradation during encoding and task demands during test modulated these results in predicted ways. The results support the theory that dissociable neural subsystems operate in parallel (not in sequence) to underlie visual object recognition: An abstract-category subsystem operates more effectively than a specific-exemplar subsystem in the left hemisphere, and a specific-exemplar subsystem operates more effectively than an abstract-category subsystem in the right hemisphere.What would you name each of the two objects in Figure 1? Most people would name them both "piano," even though they obviously are different exemplars of pianos. This is a simple, but interesting, observation because it indicates that the two shapes are recognized as the same in one sense, but different in another. If so, the visual system is confronted with contradictory recognition problems: How can it recognize that those objects belong to the same (abstract) category, but also to different (specific) categories? Contemporary theories of object recognition ignore the opposing natures of these abilities and posit that a single, undifferentiated system accounts for the visual-structural processing underlying object recognition. However, computational reasoning and functional hemispheric asymmetries suggest that the human brain may solve the dilemma by implementing dissociable subsystems to underlie abstract and specific recognition . This article reports experiments directly supporting the dissociable-subsystems theory.The two relevant abilities may be defined as follows. Abstractcategory recognition refers to the ability of the visual system to learn to map different input shapes, even fairly dissimilar ones, to the same output representation. In contrast, specific-exemplar recognition refers to the ability to learn to map different input shapes, even fairly similar ones, to different output representations.Why hypothesize that dissociable subsystems underlie abstractcategory and specific-exemplar object recognition? Recent evidence indicates that at least relatively independent subsystems underlie abstract and specific recognition of word forms (Marsolek, Kosslyn, & An abstractcategory subsystem that operates effectively in the left cerebral hemisphere (LH) stores such forms in an exemplar-abstract manner, whereas a specific-exemplar subsystem that operates effectively in the right cerebral hemisphere (RH) stores such forms in an exemplarspecific manner. For e...

Visual-form systems in the cerebral hemispheres were examined in 3 experiments. After learning new types of visual forms, participants rapidly classified previously unseen prototypes of the newly learned types more efficiently when the forms were presented directly to the left hemisphere (in the right visual field) than when the forms were presented directly to the right hemisphere (in the left visual field). Neither previously seen nor previously unseen distortions of the prototypes were classified more efficiently when presented directly to the left hemisphere than when presented directly to the right hemisphere. Results indicate that an abstract visual-form system operates effectively in the left hemisphere and stores information that remains relatively invariant across the specific instances of a type of form to distinguish different types. Furthermore, this system functions relatively independently of another system that operates effectively in the right hemisphere and that stores details to distinguish specific instances of a type of form.

Participants viewed objects in the central visual field and then named either same or different depthorientation views of these objects presented briefly in the left or the right visual field. The differentorientation views contained either the same or a different set of parts and relations. Viewpoint-dependent priming was observed when test views were presented directly to the right hemisphere CRH), but not when test views were presented directly to the left hemisphere CUI). Moreover, this pattern of results did not depend on whether the same or a different set of parts and relations could be recovered from the different-orientation views. Results support the theory that a specific subsystem operates more effectively than an abstract subsystem in the RH and stores objects in a manner that produces viewpointdependent effects, whereas an abstract subsystem operates more effectively than a specific subsystem in the UI and does not store objects in a viewpoint-dependent manner.