However, we are doubtful that implementation of these ideas would dramatically change the genetic landscape for P3 or our conclusions about its genetic architecture. High heritability is not a requirement, nor does it portend success, for finding SNPs or rare variants. The multivariate P3 genetic factor score we examined has a heritability of 1.0 yet produced results that varied indistinguishably from those associated with P3 amplitude. Moreover, heritability varied across the set of endophenotypes from exceptionally high (~.85) to zero, yet the likelihood of obtaining significant molecular-genetic results clearly did not depend on endophenotype heritability; approximately 30% of the filled cells in Table 1 are for affective modulated startle indices, which are the least heritable of our measures. Nor did the likelihood of obtaining a significant “hit” depend on the apparent complexity of the endophenotype; those with the simplest neural circuitry, such as electrodermal orienting and eye blink startle, were no more likely to produce an association than the more complex ones.
