MOUSE PAW PREFERENCE - EFFECTS OF VARIATIONS IN TESTING PROTOCOL

TWO experiments using two inbred strains of mice were conducted to stu dy mouse paw preference. In the first study, 250 (50 x 5) paw reaches from each of 12 male and 12 female C57BL/6J mice were observed over an 8-week period using the Collins paw preference apparatus to investiga te questions relating to the independence of reaches, the size of the tube into which the animals reach for flakes of food, and practise eff ects. Animals appeared to be much more highly lateralized when two ind ependent reaches per day for 25 days (I protocol) were observed than w hen 50 reaches were observed in a single session (S protocol). Paradox ically, however, we found no evidence for the lack of independence of reaches when we examined the sequences of reaches performed by animals under the S protocol conditions. With practise, animals became slight ly more lateralized, but there were no effects of sex, and approximate ly equal numbers of mice were left-pawed as were right-pawed. The size of the tube had no effect. The second study used 30 BALB mice, each o f which was tested with both the I and S protocols, with order of test ing counterbalanced. There was a significant protocol x order interact ion such that those doing S first were more highly lateralized on the I task, but those doing I first were highly lateralized on both tasks. (C) 1997 Elsevier Science Ireland B.V.