Lesions in either the proposed parietal or temporal cortex resulted in a dissociation of deficits, with the former affecting maze performances and "complex" but not "simple" pattern discrimination and the latter affecting performances on a series of reversals and the simple but not the complex pattern discrimination. Discussion considered the role of parietal cortex in spatial behaviors, the adequacy of the simple and complex patterns to differentiate simple sensory from integrative functions, and the unqualified use of Lashley's principles of mass function and equipotentiality. It was also suggested that the rat might provide a useful model for investigations of posterior association cortex.The question of the existence and location of a homolog in rats to the posterior association cortex in primates was discussed recently . It was suggested that one might argue that the rat had a homolog of primate association cortex and that Lashley's work (1941; see Figures 15 and 18) might be used as the guide to the locations of the parietal and temporal association areas in the rat. Thomas and Weir also presented evidence which confirmed Thomas ' (1970) suggestion that Lashley's (1929) early data had provided questionable support for the equipotentiality of neocortical areas for maze III performance. Lesions in the parietal association area and medial frontal lesions resulted in significant performance decrements on maze III, whereas lesions of equivalent size in the frontopolar area did not.The present work was intended to investigate further the possible functions of the proposed parietal and temporal association areas in the rat as well as to assess the generality of findings and conclusions concerning association vs. sensory cortex reached by Diamond and his associates using the tree shrew (Tupaia gUs). To these ends, studies were done using (a) the Hebb-Williams mazes described by Rabinovitch and Rosvold, 1951, and (b) the "simple" and "complex" pattern discriminations and (c) the black-white discrimination reversal problems similar to those described and used by

Four squirrel and four Cebus monkeys were trained on five-trial oddity problems. Two of each species were then given problems where the odd object was reversed randomly on Trials 2, 3, or 4. They were then given one-trial oddity problems. All reached criterion in initial training. One Cebus reached criterion in reversal training, but the others showed significant improvement. All monkeys receiving one-trial oddity training responded correctly on 80% of 40 consecutive problems within 80 problems. No reliable differences were seen between the species. Discussion concerned the measures required to conclude that an animal has the oddity principle, and it was suggested that no nonprimate has been shown to master oddity.