Individuals can be categorized into four groups based on self-reported preferences for behaviors and interactions, labeled as high dopamine (sensation-seeking, novelty-seeking, spontaneous), high serotonin (stability-seeking, rule-following, traditional), high testosterone (directive, assertive), and high estrogen (nurturing, agreeable to decisions).

“So we have dopamine, serotonin, testosterone, and estrogen. Now that might seem like an unfair overgeneralization, but what's interesting is not necessarily the name or the neurochemical system, right? Those could have just been called category one, two, three and four for all that matters here. What is interesting is seeing how those different groups of individuals that she absolutely can categorize based on their self-reported preferences about behaviors and certain kinds of interactions.”