Amodal Completion: Mental Imagery or 3D Modeling?

Abstract

In amodal completion the mind in some sense completes the visual perceptual representation of a scene by representing parts of the scene hidden behind other objects. Cognitive science has had a lot to say about how amodal completion occurs but has had little to say about the format of the representations involved and the way in which they represent. Some philosophers hold that amodal completions take the form of sensory imaginings of the occluded portions. This theory poses a puzzle for both philosophy and neuroscience about how the occluded parts are imagined to be located relative to the unoccluded parts. A better theory begins with the observation that for many purposes it is useful to suppose that the mind contains mental models of three-dimensional structure. Visual perceptions and mental images may be conceived as mental models that represent external scenes by virtue of homomorphism and which possess both a deep aspect, representing both visible and occluded three-dimensional structure, and a perspectival aspect, representing only an arrangement of visible surfaces. In these terms we can explain various problem-solving abilities, such as the ability to imagine what a scene will look like from another point of view. Amodal completions can be treated as deep perceptual representations of three-dimensional structure. Thus amodal completions do not consist of mental imagery, but they can be used to generate mental imagery representing how a scene would look from alternative points of view.