The purpose of the present study was to examine Kosslyn's (1987) claim that the left hemisphere (LH) is specialized for the computation of categorical spatial representations and that the right hemisphere (RH) is specialized for the computation of coordinate spatial representations. Categorical representations involve making judgments about the relative position ofthe components of a visual stimulus (e.g., whether one component is abovelbelow another). Coordinate representations involve calibrating absolute distances between the components of a visual stimulus (e.g., whether one component is within 5 mm of another). Thirty-two male and 32 female undergraduates were administered two versions of a categorical or a coordinate task over three blocks of 36 trials. Within each block, items were presented to the right visual field-left hemisphere (RVF-LH), the left visual field-right hemisphere (LVF-RH), or a centralized position. Overall, results were more supportive of Kosslyn's assertions concerning the role played by the RH in the computation of spatial representations. Specifically, subjects displayed an LVF-RH advantage when performing both versions ofthe coordinate task. The LVF-RH advantage on the coordinate task, however, was confined to the first block of trials. Finally, it was found that males were more likely than females to display faster reaction times (RTs) on coordinate tasks, slower RTs on categorical tasks, and an LVF-RH advantage in computing coordinate tasks. Kosslyn (1987) proposed that the human visual system computes two types of spatial representations, and that the processing subsystems responsible for the computation of these distinct representations are lateralized to different cerebral hemispheres. One purpose of the present study was to examine the generalizability of this claim by using two versions of a visual-spatial processing task. A second purpose was to examine individual differencesparticularly sex differences-in the computation of different types of spatial representation. Kosslyn argued that the left hemisphere (LH), because of the important role that it plays in language functioning, becomes specialized for computing categorical spatial representations. Categorical spatial representations involve the determination of whether the components of a multipart, nonrigid visual stimulus share a generalized, abstract relationship with each other (e.g., whether one component is "outside of," "on top of," or "attached to" another component). Kosslyn also maintained that the right hemisphere (RH), beThis researchwassupportedin part by NIAResearch Grant AG06041 to W. 1. Hoyer. We wish to acknowledge theassistance ofScottl0hns0n in task development, Mehmet Yavuzer in programming, and Carl Crockett

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The authors examined episodic and semantic contributions to 2 salient features of older adults' autobiographical recall: the reminiscence bump and the retention effect. Forty well-educated and healthy older men (mean age = 72.5 years; SD = 1.1) recalled personal memories in response to a series of cue words. They also categorized each memory as something they remembered from the past (R response) or they knew had happened in the past (K response) and indicated their ages when each memory occurred. The authors assumed that R and K responses reflected the operation of the episodic and semantic memory systems, respectively. Results showed a reminiscence bump and a retention effect for both R and K responses. The authors discuss the implications of this finding concerning the purported bases of the reminiscence bump and the retention effect as well as the notion that aging is more likely to effect episodic memory than semantic memory.

Age and brain hemispheric differences in visual-spatial performance were investigated using 2 versions of categorical and coordinate (metric) spatial relations tasks. Thirty-two young adults (M -19.2 years) and 32 older adults (M= 68.8 years) participated. An overall age-related decrement in computing visual-spatial relations was obtained for lateralized presentations and when items were presented centrally. In contrast to some previous findings, there was no evidence to suggest differential aging of the right hemisphere in computing visual-spatial relations.This research was supported by National Institute on Aging Research Grant AG 06041 to William J. Hoyer. Data reported for the young subjects in this experiment were also described in an article by John M. Rybash and William J. Hoyer (1992).We acknowledge Christine Chiarello and Jeffrey Elias for their helpful comments on an earlier version of this article. Also, we acknowledge Carl Crockett, David Hattenbrun, Kjmberly Potts, and Chandan Vaidya for assistance with data collection and Mehmet Yavuzer for programming assistance. We thank members and staff of the Wagon Wheel Senior Center in Syracuse, New \brk, for their cooperation.

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