The reason for this is that ‘heritability’ is not a fixed quantity
for each trait, to be measured once in one environment and
then applied to all other situations (Feldman & Lewontin
1975). Heritability and the apparent genetic correlations
between different traits depend on: i) the range of genotypes
that have been looked at; and ii) the range of environments
in which they have been reared, so that heritability measured
in one set of environments cannot readily be extrapolated to
another. For example, the heritability of learning ability
among six strains of mice was found to vary by a factor of
10 (0.4 to 4.0) depending on whether they had been reared in
enriched cages or standard laboratory ones (Henderson
1970).