Processing of the Global and Local Dimensions of Visual Hierarchical Stimuli by Humans (Homo sapiens), Chimpanzees (Pan troglodytes), and Baboons (Papio papio)

Abstract

A well-known phenomenon in the literature on human perception is the global precedence effect, which was initially reported by Navon in 1977. Navon presented human subjects with hierarchical stimuli such as those shown in Fig. 1. These were large letters (global level) made up of smaller letters (local level) which had to be identified as quickly as possible. Use of these forms showed that response latencies were shorter on average for the global trials, involving identification of the global letter, than for the local trials, involving identification of the local letter. It was also shown that response times (RTs) in global trials remained unchanged whatever the identity of the letter shown at the local level, whereas RTs in local trials were higher when the global and local levels showed different letters than when they showed the same letter. On the basis of these results, (1977) suggested that the processing of visual stimuli by humans proceeds from an analysis of the global structure of the visual form prior to the analysis of its more local details. According to (1977), this global-to-local order of visual processing is a general trait of visual perception, and is independent of the use of hierarchical letter stimuli, as revealed by the title of his article “Forest before the tree: the precedence of global features in visual perception.”