Social Approach-Avoidance Test

The social approach-avoidance test quantifies an animal's motivation to seek proximity to a social target versus actively avoiding it, serving as a sensitive readout for social withdrawal following chronic stress, social defeat, or in models of social anxiety. The apparatus consists of an open field arena (typically 42 x 42 cm) with a small wire mesh enclosure (10 x 6 cm) centered against one wall that can hold a social target mouse. The test is run in two consecutive phases: a first phase with an empty wire mesh cage (no social target) to measure baseline exploration, followed by a second phase with an unfamiliar social target mouse placed inside the cage. Comparing behavior across phases isolates the social-specific component of approach or avoidance from general anxiety-like behavior.

The key metric is the social interaction ratio, calculated as time spent in the interaction zone when the social target is present divided by time in the same zone when the cage is empty. Ratios above 1.0 indicate social approach (normal in unstressed C57BL/6 mice), while ratios below 1.0 indicate social avoidance, which is the hallmark behavioral signature of susceptibility to chronic social defeat stress. The corner zone ratio quantifies time spent in corners opposite the social target, with elevated corner time reflecting active avoidance rather than passive non-engagement. This two-zone metric system allows discrimination between susceptible and resilient phenotypes within defeated cohorts, as resilient mice show interaction ratios similar to non-defeated controls despite equivalent stress exposure.

ConductMaze defines configurable interaction and corner zones relative to the wire mesh cage position, tracking the subject animal via overhead video across both empty-cage and social-target phases. The system automatically transitions between phases after the user-defined interval, computing zone occupancy times, entry frequencies, and locomotor parameters separately for each phase. The social interaction ratio and corner zone ratio are calculated immediately upon trial completion, and batch analysis generates susceptible-resilient classification thresholds based on user-defined cutoffs or population-derived z-score criteria across the full defeated cohort.