In Chapter One (What Is Psychology?) the importance of critical thinking was not

Heritability is defined by geneticists as a statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within a group.
Estimates of heritability apply only to a particular group living in a particular environment and apply only to the group and not to individuals.
High heritability means that a high percentage of the variability of a particular trait within the group is due to genetic factors.
High heritability does not mean that the environment is not a factor.  Even highly heritable traits can be modified by the environment.