LEB mice of both replicates moved less during the selection test at the fifth generation of selection (main effect of line at S5, F1,128 = 39.48; P < 0.0001; see Fig. 2 C and D) as well as during all other correlated response testing (data not shown). The mice selected as breeders for both LEB lines moved substantially less than the population mean and particularly less than the HEB breeding pairs. The HEB mice selected as breeders, however, did not differ substantially from the population mean for locomotion at any generation of selection, indicating that the selection response for head dips in the upward direction, at least, was not driven solely by selection for high activity.
