Content Warning: This section of the guide includes discussion of mental illness.

Gibson examines the personality traits and behavioral patterns of “internalizers”—individuals who are highly attuned to emotions and process their experiences internally. Internalizers are exceptionally perceptive people who notice subtle emotional cues that others might miss. This heightened sensitivity allows them to register emotional hurt more deeply than “externalizers,” who act out their feelings through behavior. Gibson suggests this perceptiveness may have neurological foundations, pointing to research indicating that some babies demonstrate greater attentiveness to their surroundings from an early age.

Internalizers experience emotions intensely but tend to hold them inside rather than acting them out immediately. This internalization allows emotions to build in intensity. Because of this tendency to display their emotions rather than act them out, internalizers may be labeled as “too sensitive” by emotionally immature parents who find emotional displays uncomfortable. A defining feature of internalizers is their profound need for genuine emotional connection. Gibson explains that this desire for authentic engagement is a healthy mammalian trait that helps regulate stress responses. According to neuroscience research Gibson cites, mammals have evolved mechanisms that allow them to calm their physiological stress reactions through social connection.