Effects of the light–dark cycle on a water tank social interaction test in mice.
Mice were exposed to a water tank interaction test in which food could be obtained either by wading in the water or by attacking littermates. A tank with progressively rising water levels caused mice in groups of four to differentiate into those willing to wade (carrier mice) from those unwilling to wade (noncarrier mice). Noncarrier mice could only obtain food by stealing it from carrier mice or from other noncarrier mice. It was found that mice during the dark period