Locomotor activity in the initial test in a novel environment was highly correlated with activity recorded concurrently in all other novelty seeking tests (all r > 0.8 and P < 0.01; see Fig. 5) as well as with the number of head dips and preference for a novel environment. Given this strong relationship between locomotion and most dependent measures, we examined the pattern of correlations that resulted after correcting statistically for the contribution of locomotion by regressing the main dependent measure from each task on locomotion as measured in that task. The result was a residual score for each mouse that reflected the degree to which this individual deviated from the best-fit regression line, and this residual was explicitly uncorrelated with locomotion (r = 0). Strain means were then calculated from individual residual scores, and genetic correlations among the mean residual scores were calculated. Residuals had a heritable component equal to or slightly less than that of the main dependent measure for each task (see Table 1), and the overall pattern of correlations among the remaining dependent measures was unchanged,
