Abstract
Our minds can represent not only how the world is, but also how the world could be. For example, when completing a jigsaw puzzle, we can appreciate not only the shapes of individual puzzle pieces, but also their potential to form a new object with a shape of its own: the complete puzzle that the pieces could make. What is the nature of this experience? Might such “possible” objects be treated like actual objects by mechanisms of attention and visual cognition? Here, we show that this is the case, by demonstrating a surprising connection between possibility and perceived numerosity. Subjects saw brief displays of “puzzle piece” shapes, and were simply asked how many shapes were in each display (in particular, which of two displays had more). Crucially, the shapes appeared in pairs that either could or could not efficiently combine into new objects. For example, pieces with triangular protrusions appeared near pieces with triangular indents (such that they could combine into a single piece); or, pieces with triangular protrusions appeared near pieces with rectangular indents (such that they could not combine into a single piece). Remarkably, displays with combinable pieces were perceived as less numerous than displays with non-combinable pieces—as if the mind treated two geometrically compatible pieces as being the single object they could create. Follow-up experiments replicated this result in a larger sample, ruled out confounding geometric factors, and explored how configural processing produces these effects. For example, pairs of combinable pieces were also seen as less numerous when oriented inward (with compatible protrusions and indents facing each other) than when oriented outward (with compatible protrusions and indents facing away). We suggest that the mind confers objecthood not only on actual objects, but also on possible objects—and in ways that alter downstream visual processing.