The target article approaches individual differences in terms of phenotypic differences developing through the interaction between a specific genetic make up and environmental variables. This interaction is proposed to be cooperative and oriented toward a progressive stabilisation of the trait. However, experimental data from animal studies indicate that environmental pressure promotes dramatic changes in phenotypic expression in mature organisms. Indeed, environmental constraint not only promotes the phenotypic expression of facilitated VTA-NAS DA transmission in genotype-resistant individuals; it also inhibits its expression in genetically prone individuals. This is in line with negative genotype-environment correlation revealed by behavior genetics.