Dawei Bai¹ (), Brian Scholl¹; ¹Yale University

The perception of multiple shapes depends on how they are arranged: you might see distinct objects, or you might see a single *group*. What cues drive such grouping? Classic answers involve simple physical relationships such as proximity or common motion. Here, in contrast, we ask whether perceptual groups can also be formed by *social* cues — as when the movement of simple shapes triggers an impression of goal-directed agency. To find out, we explored the flip-side of grouping: loss of individuality. Previous work has shown that when observers must quickly estimate the number of discs in a display, for example, estimates will be lower when pairs of discs are grouped by thin lines. Does social grouping due to shared goals lead to a similar loss of individuality? Observers viewed short (e.g. 1.5 s) animations of moving ‘dart’ shapes. Darts moved randomly, but rotated so as to continuously point at a common target (a moving disc). This display yields a vivid impression of collective goal-directed behavior (known as the Wolfpack effect): despite the random movement, the shapes appear to share the common goal of pursuing the target. In contrast, when darts are always oriented 90° away from the target (thus equating rotary motion correlation), such impressions are destroyed. Observers viewed variable numbers of darts, and simply estimated how many were present on each trial. The results were striking: numerical estimates were reliably lower for Wolfpack displays compared to equated 90°-rotation displays — and this was true for a range of different numerosities, and even for observers who reported not noticing the darts’ related orientations. This suggests that shared goals can lead to perceptual grouping and a corresponding loss of individuality. In this way, social groups may be central not only to social cognition, but also to visual processing.