TEMPORAL STRUCTURE OF OPEN-FIELD BEHAVIOR IN INBRED STRAINS OF MICE

Behavior of the inbred mouse strains BALB, C3H, DBA and C57BL in an open field was directly observed for 10 min by a multi-event time sampling method. It was coded into nine behavioral items, the occurrence or absence of which in consecutive 5-s time bins was called a behavioral state. Fourteen states appeared to be sufficient to describe the behavior of all strains. Sniffing was the most common behavioral item and a component of nearly all behavioral states. In Analysis 1, sequential relations between behavioral states were obtained. In Analysis 2, the temporal structure of behavior was explored further by principal component analysis. Both revealed the same essential features. Immediately after introduction into the open-field, mice showed a more or less strong stretching tendency, which disappeared sooner or later and was replaced by behaviors like locomotion, rearing and leaning against wall. The change occurred quite soon in C57BL as well as in DBA, later in C3H and hardly in BALB during the observation period. It is suggested that the observed stretching tendency is the behavioral expression of emotional arousal evoked on introduction into a novel situation.