Abstract
In the last two decades, comparative research has addressed the issue of how the global and local levels of structure of visual stimuli are processed by different species, using Navon-type hierarchical figures, i.e. smaller local elements that form larger global configurations. Determining whether or not the variety of procedures adopted to test different species with hierarchical figures are equivalent is of crucial importance to ensure comparability of results. Among non-human species, global/local processing has been extensively studied in tufted capuchin monkeys using matching-to-sample tasks with hierarchical patterns. Local dominance has emerged consistently in these New World primates. In the present study, we assessed capuchins' processing of hierarchical stimuli with a method frequently adopted in studies of global/local processing in non-primate species: the conflict-choice task. Different from the matching-to-sample procedure, this task involved processing local and global information retained in long-term memory. Capuchins were trained to discriminate between consistent hierarchical stimuli (similar global and local shape) and then tested with inconsistent hierarchical stimuli (different global and local shapes). We found that capuchins preferred the hierarchical stimuli featuring the correct local elements rather than those with the correct global configuration. This finding confirms that capuchins' local dominance, typically observed using matching-to-sample procedures, is also expressed as a local preference in the conflict-choice task. Our study adds to the growing body of comparative studies on visual grouping functions by demonstrating that the methods most frequently used in the literature on global/local processing produce analogous results irrespective of extent of the involvement of memory processes.
Highlights
An important issue in visual cognition is the extent to which visual processing identifies local elements first and only subsequently integrates them into whole objects, or vice versa, detects the global properties of objects before an analysis of its component parts
We evaluated if: (1) the percentage of local choices was significantly higher than the 50% expected by chance; (2) the percentage of local choices differed between the two groups of subjects reinforced with different hierarchical figures; (3) the Response Time (RT) differed between local and global choices; (4) the percentage of correct choices for nonhierarchical stimuli was significantly above chance level
This study shows that tufted capuchin monkeys rely on local elements in a conflict-choice task featuring Navon-type hierarchical stimuli
Summary
An important issue in visual cognition is the extent to which visual processing identifies local elements first and only subsequently integrates them into whole objects, or vice versa, detects the global properties of objects before an analysis of its component parts. A relative bias towards the processing of the local features of objects or their global configuration, in terms of accuracy or speed of processing, has often been regarded as indicative of the perceptual strategy used by a given species. Comparative studies in this area are inspired by a seminal article by Navon (1977). Navon (1977, 1981) demonstrated that human adults tested with hierarchical visual patterns, i.e., local elements spatially arranged to form global configurations, process the global configuration more accurately and faster than the local elements Evidence confirming this global advantage in humans has been provided in several other studies
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