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Local advantage in the visual processing of hierarchical stimuli following manipulations of stimulus size and element numerosity in monkeys (Cebus apella)

By Giovanna Spinozzi, Carlo De Lillo and Valeria Salvi

Abstract

This article was published as Behavioural brain research, Vol. 166, (2006), pp.45-54. It is available from: \ud http://www.sciencedirect.com/science/journal/01664328Metadata only entryPrevious studies suggest that monkeys process local elements of hierarchical visual patterns more quickly and more accurately than they\ud process the global shape. These results could be indicative of differences between relatively high visual functions of humans and non-human\ud primates. It is, however, important to rule out that relatively low-level factors can explain these differences. We addressed this issue with\ud two experiments carried out on capuchin monkeys (Cebus apella) using matching-to-sample tasks featuring hierarchical stimuli. The first\ud experiment assessed whether manipulations of stimulus size can affect the local advantage so far observed in this NewWorld monkey species.\ud An overall local versus global advantage still emerges in capuchins, irrespectively of the amplitude of the visual angle subtended by the\ud hierarchical shapes. Moreover, a local-to-global interference, indicative of a strong local advantage, was observed for the first time. In the\ud second experiment, we manipulated size and numerosity of the local elements of hierarchical patterns, mimicking procedures that in human\ud perception relegate the local elements to texture and enhance a global advantage. Our results show that in capuchin monkeys, a local advantage\ud emerges clearly even when these procedures are used.\ud These results are of interest since extensive neurophysiological research is carried out on non-human primate vision, often taking for granted\ud a similarity of visual skills in human and non-human primates. These behavioural results show that this assumption is not always warranted\ud and that more research is needed to clarify the differences in the processes involved in basic visual skills among primates

Topics: Perceptual grouping, Hierarchical stimuli, Local, Global, Primates, Capuchin monkeys
Publisher: Elsevier
Year: 2006
DOI identifier: 10.1016/j.bbr.2005.06.043
OAI identifier: oai:lra.le.ac.uk:2381/7506
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