"Shall two walk together except they be agreed?" Spatial behavior in rat dyads.

When animals explore an unfamiliar environment, they gather information that enables them to form a cognitive representation of that environment and to use it subsequently in traveling there. In the present study, rats were tested in a large arena as singles, then in dyads, and finally, again as singles, in order to examine the effect of the social environment on exploration. Traveling in dyads facilitated exploration compared to the behavior of the same rats when they explored alone. Specifically, each rat in a dyad traveled a greater distance with higher velocity and took wider turns compared to its lone traveling. Moreover, rats in dyads spent a long time together, shared a home base, and when traveling in the same direction, one rat was leading the other. In addition to exploring the same locations, leaders explored more "private" locations, not visited by the other rat. Features of the dyad behavior were carried over to the behavior of the same rats when tested as individuals, after the dyad trial. Compared to singles, dyads represent the first step toward grouping, and it is suggested that the conspicuous change between the behavior of a rat as single compared to its behavior when in a dyad should be greater than any further changes that may occur in spatial cognitive behavior of triads, quartets, or larger groups. In other words, while the present changes in spatial cognition observed in dyads represent a small step toward grouping, they are a giant leap for the individual.