Pictorial Primates: A Search for Iconic Abilities in Great Apes

Abstract: Pictures and other iconic media are used extensively in psychological experiments on nonhuman primate perception, categorisation, etc. They are also used in everyday interaction with primates, and as pure entertainment. But in what ways do primates understand iconic artefacts? What implications do these different ways have for the conclusions we can draw from those studies on perception and categorisation? What can pictures tell us about primate cognition, and what can primates tell us about pictures? The bulk of the thesis is a critical review of the primatological literature concerned with iconic artefacts. Drawing on work in developmental psychology, cross-cultural research, and semiotics, distinctions between different kinds of pictorial competence are made. The alternatives to viewing pictures as depictions, are to view them as the real world is viewed, in which case only realistic pictures evoke recognition, or to view them as a set of disjoint properties, in which case recognition of categorisable motifs fails. It is argued that approaching a picture as a depiction entails a set of expectations on the picture, which affects attention to e.g. part - whole relationships, "filling in," and integration into context. This in turn allows recognition also of non-realistic similarity. The question, then, is whether such expectations can be formed in other brains than an exclusively human one. The different forms of pictorial competence are discussed in relation to research on similarity judgements, abstraction, and categorisation, as well as applied to other iconic media than the picture, such as scale-models, mirrors, toy replicas, and video. Two lines of original empirical investigation are presented: A study of photographic recognition in picture-naïve gorillas, and recognition of line drawings in picture-experienced and language-competent bonobos. Only the latter study yielded evidence for recognition. The failures in the former study are discussed in terms of experimental shortcomings, and suggestions for future improvements are made.