To determine the relationship of these factors to a substance use-related phenotype, we correlated the factor scores to phenotypic values from a previous study of ethanol self-administration (Phillips et al. 1994). This analysis illustrates an approach to determine which dimensions of heritable behavioral variation are most related to a specific behavioral phenotype. Correlations of alcohol preference to factor scores ranged from |r| = 0.076 to |r = 0.674, for Factor 4 for which the correlation was negative such that mice with increased startle response and anxiety-like phenotypes (manifest in our analysis as low values on the reactivity factor, Supplementary information, Table S3) had higher alcohol preference values and vice versa. This factor is regulated by a QTL on chromosome 9 which contains the Scn4b, an expression correlate of both ethanol withdrawal and Factor 4.
