For these reasons, we believe the literature on early temperament together with the developmental personality literature on person-environment transactions describes a plausible pathway for the emergence of individual differences in emotion-based disposition toward rash action. Having outlined this pathway, we want to emphasize the caveat that there are substantial limits to the stability of individual differences. In Kagan's (1994, 2003) classic research on the stability of reactivity in infants, he found that only one-third of the highly reactive infants become very fearful and later earn the label inhibited, and only one-third of the low-reactive infants later earn the label uninhibited. This finding helps clarify the limits on the developmental stability of personologic individual differences; the findings suggest stability should not be understood deterministically (Kagan, 2003), but rather probabilistically.
