Bayesian Analysis of Heterogeneous Residual Variance in Canine Behaviour

Non-additive effects like for instance genotype-environment interactions and genetically structured heterogeneity of residual variance are notoriously dependent on scale: many statistical non-additive phenomena disappear after a careful choice of transformation of the phenotypic values. Particularly for behavioural measures, scale is a delicate matter. We present a novel Bayesian approach that assesses heterogeneity in environmental variance as a function of genetic effects, where the scale is defined by a psychometric model based on item-response theory. This makes analysis results independent of what items are in a particular test version. We apply the method to fearful behaviour in dogs and compare results with the more usual sum score approach.