The effect of cage familiarity on the duration of staying in the cage during a test of open field activity. Arrows indicate the time point at which the rat's home-cage or a novel cage was placed into the open field. Solid and open bars are tests with the home and the novel cage, respectively. Control Rats were treated chronically with saline and Quinpirole Rats were treated chronically with quinpirole. Values are mean and SEM.