Memory for an edge includes figure and ground assignment

Do memories of figures code the exclusive assignment of the bounding edge to one side or do they preserve evidence that both sides of the edge were assessed for figural status? A priming task adapted from Driver and Baylis (1996) examined shape memory following a single exposure to a novel figure. The prime was a small yellow figure displayed on the left or right side of a larger red ground with a crenellated edge separating figure and ground regions. Observers viewed the prime, without making any response, and then made a speeded same-different discrimination regarding two probe shapes that were shown one above the other, either facing in the same direction as the figure prime (figure probes) or the opposite direction (ground probes). On experimental trials, at least one of the probe shapes had the same crenellated edge as the prime (different response) or both did (same response). On control trials neither of the probe shapes had the prime's crenellated edge. In Exp. 1, the prime was exposed for 180 ms, followed by a 500 ms blank screen, and then the probes. In Exp. 2, the prime was exposed for 129 ms, followed by a 129-ms mask and then the probes. In both experiments, observers were faster to respond to experimental figure probes and slower to respond to experimental ground probes than to comparable control probes, ps < .001. This result goes beyond previous studies in showing that the memory for an edge includes more than the assignment of the edge to one side (positive figure priming); it also includes memory for the abandoned assignment of the same edge to the opposite side (negative ground priming). We refer to this as memory for the "edge complex," because in addition to the shape of the crenellated edge, it includes information about which side of the edge was seen as figure vs. ground. These findings reveal the dynamics of figure-ground assignment in the absence of shape familiarity, since they were evident following a single exposure to a novel shape.