but a formal genetic analysis was not performed due to the small sample size (Carlson et al., 1997). However, a subsequent larger study (Anokhin et al., 2007a) failed to show genetic or shared environmental influences on the amount of startle modulation, although heritability of the overall startle magnitude in all three valence conditions was high (59-61%). Thus, this study found no evidence for familial influences, and individual differences in startle modulation could be attributed entirely to individually unique environmental factors.
