Experiments in Visual Perspective: Size Experience

Abstract

Phenomenal objectivism explains perceptual phenomenal character by reducing it to an awareness of mind-independent objects, properties, and relations. A challenge for this view is that there is a sense in which a distant tree looks smaller than a closer tree even when they are the same objective size (perceptual size variation). The dual content view is a popular objectivist account in which such experiences are explained by my objective spatial relation to the tree, in particular visual angle (perspectival size). I describe a series of first-person experiments for investigating size experience. I use a ruler as a first-person method for operationalising perspectival size (Experiment 1). I use the corridor illusion (Experiment 2), outlining one's head in the mirror (Experiment 3), and outlining the size of objects on glass (Experiment 4) to show a phenomenal difference in size for items in different depth contexts, despite being identical in visual angle. These finding demonstrate that visual angle cannot account for these spatial experiences. Psychological evidence provides further support for the thesis that subjects do not experience visual angle when depth information is present. Together this evidence supports the hypothesis that perceptual size variation cannot be accounted for by visual angle, hence undermining a plausible version of the dual content theory. This outcome, combined with problems raised by alternative objectivist accounts of size variation, provides support for a subjectivist account of size experience.