Editing Temperament (section)

===Kagan's research===

[[Jerome Kagan]] and his colleagues have concentrated empirical research on a temperamental category termed "reactivity." Four-month-old infants who became "motorically aroused and distressed" to presentations of novel stimuli were termed ''highly reactive''. Those who remained "motorically relaxed and did not cry or fret to the same set of unfamiliar events" were termed ''low reactive''.<ref name=Kagan2>{{Cite journal | doi = 10.2307/1131931 | last1 = Kagan | first1 = J. | year = 1997 | title = Temperament and the reactions to unfamiliarity| journal = Child Development | volume = 68 | issue = 1| pages = 139–143 | pmid = 9084130 | jstor = 1131931 | url = http://nrs.harvard.edu/urn-3:HUL.InstRepos:37980692 }}</ref> These high and low reactive infants were tested again at 14 and 21 months "in a variety of unfamiliar laboratory situations." Highly reactive infants were predominantly characterized by a profile of high fear to unfamiliar events, which Kagan termed inhibited. Contrastingly, low reactive children were minimally fearful to novel situations, and were characterized by an uninhibited profile (Kagan). However, when observed again at age 4.5, only a modest proportion of children maintained their expected profile due to mediating factors such as intervening family experiences. Those who remained highly inhibited or uninhibited after age 4.5 were at higher risk for developing anxiety and conduct disorders, respectively.<ref name=Kagan/>

Kagan also used two additional classifications, one for infants who were inactive but cried frequently (distressed) and one for those who showed vigorous activity but little crying (aroused). Followed to age 14–17 years, these groups of children showed differing outcomes, including some differences in central nervous system activity. Teenagers who had been classed as high reactives when they were babies were more likely to be "subdued in unfamiliar situations, to report a dour mood and anxiety over the future, [and] to be more religious."<ref>{{cite journal |jstor=30163598|title=The Preservation of Two Infant Temperaments into Adolescence|journal=Monographs of the Society for Research in Child Development|volume=72|issue=2|pages=i–95|last1=Kagan|first1=Jerome|last2=Snidman|first2=Nancy|last3=Kahn|first3=Vali|last4=Towsley|first4=Sara|last5=Steinberg|first5=Laurence|last6=Fox|first6=Nathan A|year=2007}}</ref>