The concept of (depth) cues: An exemplification of homuncular language in vision science

The term “depth cue” is fundamental to and widely used in vision science. However, despite the prevalence and importance of that concept, there is virtually no study on its theoretical foundations and coherence. This article aims at filling that gap by investigating both its historical development and its current use within the predominant computational approach to vision. Against the backdrop of Wittgenstein’s therapeutic approach to philosophy, it is shown that both traditional and current characterizations of depth cues suffer from a serious logical flaw known as “homunculus” or “mereological fallacy.” It is suggested that the problem of homuncular language impedes critical thinking and theorizing in vision science since it obscures the matters at issue by disguising explanatorily empty expressions as explanatory hypotheses. Furthermore, it is argued that homuncular language is not confined to the concept of depth cues but typical of current cognitive science in general since it is linked to its most fundamental assumption of the brain being an information processing system. In conclusion, resulting implications for cognitive science and cognitive scientists are considered.