Figure 2
Heritability of impulsivity. (A) Percentage of rats expressing either high (HI) and low (LI) impulsivity across the entire pedigree. 54% of rats were HI, while 46% were LI. (B) The percentage of offspring in each litter expressing HI was significantly greater in those selectively bred for high (HI x HI) rather than low (LI x LI) impulsivity (*p < 0.01, main effect of breeding, two-way ANOVA). (C) The quantitative magnitude of the impulsivity phenotype (average premature responses) was found to be significantly greater in HI offspring of litters bred selectively for HI (HI x HI) compared to LI (LI x LI), while no difference was observed for LI offspring of either lineage (*p < 0.01, main effect of breeding, ^p < 0.05, main effect of phenotype, #p < 0.05, interaction between breeding and phenotype). (D) This effect was moderated by gender, with the average premature responding of male HI rats from HIxHI pairings significantly greater than female rats within these litters, as well as male and female rats from LI x LI pairings (*p < 0.05 main effect of breeding, #p < 0.05 breeding x sex interaction). (E,F) Mid parental-offspring correlation heritability estimates (h2) confirmed a significant heritability of this trait. Shown are (E) percentage premature response means in parents (x-axis) and offspring (y-axis) and (F) absolute number of premature responses in parents (x-axis) and offspring (y-axis). Results indicate a 44% significant correlation (p = 0.00129 and h2 = 16% for data shown in (E) and a 43% significant correlation (p = 0.00182) and h2 = 13% for data shown in (F).
