Before we can recognize what an object is, the visual system must determine that an object is there — separating it from its background. Figure-ground organization is among the most basic and automatic perceptual processes, operating pre-attentively and influencing all subsequent visual processing. It determines which regions of the visual field are perceived as shaped, bounded objects and which are perceived as formless background extending behind them.
Properties of Figure and Ground
Edgar Rubin (1915) identified several asymmetries between figure and ground. The figure appears to have a definite shape defined by the shared contour, while the ground appears shapeless at the border. The figure appears closer to the observer and slightly in front of the ground. The figure is better remembered than the ground, and the figure tends to be the focus of attention. These asymmetries arise from border ownership assignment — the process of determining which side of a shared contour "owns" the border and thus has a definite shape.
Cues for Figure-Ground Assignment
Multiple cues influence which region is perceived as figure. Lower region, smaller area, convexity, symmetry, enclosedness, and greater contrast all favor figure perception. These cues are probabilistic — no single cue determines the outcome, and they can be put in conflict. When cues conflict, the visual system appears to weight them according to their reliability, consistent with a Bayesian framework.
The vase-faces figure created by Edgar Rubin is perhaps the most famous demonstration in visual perception. The same image can be seen as a white vase on a black background or as two black faces in profile on a white background. Perception alternates between these two interpretations, illustrating that figure-ground assignment is an active interpretive process and that the visual system cannot simultaneously assign both organizations — when the vase is figure, the faces are ground, and vice versa.
Neural Mechanisms
Neurons in area V2 of visual cortex show border ownership selectivity: they respond differently to the same local edge depending on which side is figure. These border ownership signals appear within 10-25 ms of the initial visual response, suggesting rapid computation involving feedback from higher visual areas. Zhou, Friedman, and von der Heydt (2000) discovered these neurons, which provide a neural correlate of one of the earliest stages of perceptual organization.
Figure-ground processing extends beyond V2 to engage V4, the lateral occipital complex, and parietal regions. Patients with damage to parietal cortex can show extinction — failure to perceive a figure on the contralesional side — demonstrating the role of attention and parietal mechanisms in figure-ground processing.
Extremal Edges and Depth
An important recent advance is the recognition of extremal edges — contours where a surface curves away from the viewer — as a powerful cue for figure-ground assignment. Extremal edges signal that the figure continues behind its visible boundary, providing both shape and depth information. This ecological cue is more robust than many classical cues and reflects the 3D structure of real-world objects.
Interactions with Attention and Recognition
While figure-ground organization has traditionally been considered a pre-attentive process, recent research shows significant interactions with attention and object recognition. Familiar shapes are more likely to be perceived as figure (the familiar configuration cue), and attention can bias figure-ground assignment. These findings suggest a more interactive relationship between early perceptual organization and higher-level cognition than the classical Gestalt view proposed.