The hierarchy of food, sociality, and experience in spatial decision-making by food-deprived rats.

We examined whether a hierarchy existed among attraction to (i) food; (ii) social partner(s); and (iii) familiar feeding location in spatial decision-making in rats. To determine this, lone food-deprived rats were trained to collect baits from 16 salient equispaced objects arranged in a grid layout. Some rats were trained with only the eight objects on the left baited; other rats with only the eight objects on the right baited. After training, dyads of one left-trained and one right-trained rats were tested, with the eight baits now divided into four on the left and four on the right sides of the arena. Rats were free either to go to the familiar objects that had been baited in the lone training trials, regardless of whether these objects were now actually baited; or, alternatively, they could go to baited objects regardless of their side and of the rats' past experience. Rats could also forage individually or together regardless of their past experience or actual bait location. We found that the rats primarily displayed attraction to baits, regardless of their location; followed by a preference to travel together; and then by a significant combined attraction to visit together baited objects (whether familiar or not). Accordingly, attraction to food had the prime influence, sociality the second, and familiarity with the environment the least, in establishing spatial foraging decisions.