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Mou, Zhao, and McNamara (2007) proposed the "intrinsic model of human spatial memory," which posits that a viewer's memory of an array of objects will exhibit a preferred direction that is aligned with an intrinsic axis of the array. They defined intrinsic axes as salient axes created in part by the physical (geometric) properties of the array. To date, these geometric characteristics have received little research attention. We begin such an endeavor by evaluating the role of symmetry and orthogonality (i.e., number of right angles in an array of objects) in spatial memory. Participants viewed a layout of objects from a single (Experiment 1) viewpoint or 2 (Experiment 2) viewpoints and then judged relative directions within the layout from memory. Orthogonality and symmetry were associated with decreased reliance on egocentric reference systems but were qualified by a generally greater reliance on egocentric reference frames than is common in the literature. Indeed, for only 1 array--a highly orthogonal and symmetric one--did participants consistently respond nonegocentrically. We suggest that overuse of this array in the literature has led to an overestimation of the importance of allocentricity in spatial memory. [ABSTRACT FROM AUTHOR]

To investigate the ability of aged monkeys to plan and the effect of aging on this ability, performance in a food retrieval task was assessed in aged and younger Japanese monkeys (Macaca fuscara). In this task, the monkeys had to retrieve food items by selecting from a set of 9 holes, each of which contained I food item. Results showed that task performance declined significantly with age. All monkeys showed, to a greater or lesser extent, some consistent patterns in their sequence of selecting holes for retrieving the food item. An analysis of these selection patterns indicated that the younger monkeys showed more consistent sequences in selection than the aged monkeys. Furthermore, success in the task performance correlated strongly with higher consistency in the sequence of selecting holes. The authors simulated performance for this task by monkeys without any strategies or plans. The results suggest that the empirical data were far more systematic than the simulated data. Thus, the authors conclude that Japanese monkeys have the ability to plan and that this ability to plan deteriorates with age. [ABSTRACT FROM AUTHOR]