All inbred mice were tested serially through the following five tests in this order: activity in a novel environment; novel environment preference; head dipping on a hole-board; object preference on the hole-board; and spontaneous alternation in a Y-maze. In the first pass of these experiments, novel object recognition was also evaluated, but, because of problems with the procedure, this task was not used in the second pass, and the data are not shown. At each generation of selection of HEB and LEB mice, the testing procedure was similar to that used for the inbred strain experiments, with the exception that the mice were first tested on the hole-board, followed by object preference, novel environment preference, and spontaneous alternation. The testing order for the selection experiments was changed to measure head dipping, the trait for which the mice would be selectively bred, in experimentally naïve mice. Activity in a novel environment was not included in the report of the selection because of high correlations among locomotor activity scores seen in inbred strains. More details of behavioral testing are given in Supporting Text.
