To characterize the relationships among the variables further we also performed a principal-components analysis of the individual phenotypic data from all of the novelty seeking measures. This analysis is described in Supporting Text, and the results are shown in Table 5. Unlike the genetic correlations, the principal-components analysis indicated that, at the phenotypic level, novel environment and object preference are more closely associated with each other than they are with any other trait. Therefore, we wished to test the relationships among the tasks further by using a second genetic approach: selective breeding for high and low head dipping as measured in the hole-board apparatus.
