Approach, avoidance, and contact behavior of individually recognized animals automatically quantified with an imaging...

A low-cost system was developed that allows the assessment of the location and the direction of movements of two individually recognized animals in a social interaction. The program was validated by (i) assessing deliberately induced approach and avoidance movements of artificial objects, (ii) the effects of known differences in social behavior between differently treated rats, and (iii) repeatedly testing social behavior under similar circumstances to assess enhanced social contact due to being familiar with the arena. Movements toward and away from each other of individually housed versus group-housed animals, and of young versus aged animals, were analyzed by the system. The results obtained, demonstrated that in the case of randomly moving artificial objects specific approachers or avoiders could not be identified, whereas isolated and young rats showed more approach behavior than their respective controls. In addition, the algorithm applied for calculating relative approach and avoidance movements elucidated differences between groups that were not noticed by human observers. Social contact behavior of rats was assessed automatically. Habituation to the testing situation in repeated testing increased social contact behavior.