Global and local processing of hierarchical visual stimuli in tufted capuchin monkeys (Cebus apella).

Abstract

Consiglio Nazionale delle RicercheCapuchin monkeys' (Cebus apella) relative accuracy in the processing of the global shape or the local features of hierarchical visual stimuli was assessed. Three experiments are presented featuring manipulations of the arrangement and the density of the local elements of the stimuli. The results showed a clear advantage for local level processing in this species, which is robust under manipulations of the density of the local elements of the stimuli. By contrast, the density of the component elements linearly affected accuracy in global processing. These findings, which support those from other studies in which a local superiority emerged in animals, challenge the generality of early claims concerning the adaptive value of global advantage in the processing of hierarchical visual patterns.On the basis of his findings concerning the perceptual processing of visual stimuli, Navon (1977, 1981) argued that the human perceptual system processes the global features of a visual scene before proceeding to a more fine-grained analysis of local details. This hypothesis, termed the global dominance or global precedence hypothesis (Navon, 1977), was supported by the results of a series of experiments in which adult subjects were presented with hierarchically structured stimuli consisting of large letters made up of small letters. Navon observed that the accuracy and latency for visual detection response were better and shorter, respectively, when participants had to attend to global aspects of compound stimuli than when they were required to attend to their local features. Furthermore, in conditions in which attention had to be directed to local features, but not in conditions in which attention had to be directed toward the global form of the stimuli, the identity of the global level letter did affect subjects' discriminative responses. Global characters that conflicted with the local ones (e.g., a large S made of small Hs) slowed down the perception of local level stimuli, whereas the identity of the local elements did not affect the recognition of global level hierarchical patterns. Navon interpreted this global-to-local interference as evidence for his global precedence hypothesis.

A Comparative Analysis of Global and Local Processing of Hierarchical Visual Stimuli in Young Children (Homo sapiens) and Monkeys (Cebus apella).

“…In particular, on the basis of our first two experiments with children and the results obtained by Spinozzi et al (2003) with capuchins, we expected that the processing of the global level of the stimuli should be more easily affected by the manipulation of stimulus density in monkeys than in children.…”

“…The overall procedure was made as similar as possible to that used with monkeys by Spinozzi et al (2003). The most conspicuous differences between the two procedures were that, for the monkeys, an extended MTS training, prior to the testing with compound stimuli, was used to convey information about the nature of the task and that each monkey received a total of 96 trials instead of the 32 trials administered to the children.…”

“…Therefore, we tested children using stimuli, apparatus, and procedures that were as similar as possible to those used with monkeys by Spinozzi et al (2003). Our experimental manipulations included the presentation of consistent stimuli (hierarchical patterns in which the shape of the local elements was the same as the global shape of the stimulus) and inconsistent stimuli (hierarchical patterns in which the shape of the local elements was different from the shape at the global level).…”

Effects of brief time delays on matching-to-sample abilities in capuchin monkeys (Sapajus spp.)

“…All subjects were adults (age range: All monkeys were already familiar with the Simultaneous MTS procedure because they had been tested with a touchscreen based apparatus in tasks involving categorisation of visual stimuli and abstract concept acquisition [30,40]. Moreover, one monkey, Pippi, had been previously trained on tasks involving visual pattern discrimination (e.g., [41,42]). …”

The forest or the trees: preference for global over local image processing is reversed by prior experience in honeybees

“…These stimuli offer two dissociated levels of analysis: a local featural level composed of small elements and a global configurational level created by the spatial arrangement of local features (see examples in figure 1a). Studies in animals have reported that contrary to humans, species such as pigeons and monkeys exhibit local over global predominance in visual processing (baboons [9,10]; capuchins [17]; rhesus monkeys [18]; chimpanzees [11,18]; pigeons [19][20][21][22][23]). The causes for this difference between humans and the non-human animals studied so far remain unknown.…”