Propinquity effect

Biological Parallel

Cliff-nesting seabirds like guillemots form pair bonds almost exclusively with individuals nesting within a few feet—spatial proximity predicts partnership far more than any quality assessment. This proximity preference evolved because in dense colonies, coordinating with nearby neighbors reduces conflicts over territory and enables cooperative chick defense. The propinquity effect is minimized coordination costs: when cooperation requires repeated interaction, evolution favors bonding with the nearest available partners to reduce the energetic and temporal costs of long-distance coordination.