Goleman describes a research experiment in which infants are presented with successive new toys at 20-second intervals. Goleman states that some infants love the novelty and others hate it, beginning to cry. This illustrates the inherent trait of “inhibitedness,” a neurotransmitter pattern that makes the baby’s amygdala more excitable and thus prone to becoming overstimulated by new sensations and experiences.

A second anecdote, however, points to caregiver action as a potential treatment for inherent anxiety. Researcher John Crabbe observed that genetically identical mice nevertheless had very distinct reactions to novel situations, some of them clinging to the walls of a new space and others adventuring into the center with confidence. Crabbe believes that the variability of different caregivers, some confident and skilled and others nervous or clumsy, had a noticeable impact on the behavior of the mice.

Though all the mice possess the same genes, environmental factors change the way those genes are expressed in different individuals. The influence of environment and experience on genetic expression is known as “epigenetics.” Goleman uses the term “social epigenetics” to refer to epigenetics as it pertains to social interaction.

Goleman describes a study of genes associated with aggression.