Surgency is a trait aspect of emotional reactivity in which a person tends towards high levels of positive affect. It has been linked to the Big Five personality traits of extraversion in children. In children, surgency is an emotional dimension that is characterized by high levels of activity and positive emotion, impulsivity, and engagement with their environment.
Even though nowadays surgency is referred to as a self-reported construct, it was also associated to an ability. High surgency in children is often identified by parental self-report and has been associated with lower levels of effortful control. Thurstone and Thurstone identified surgency by the word "fluency". This concept of fluency is very broad, and includes facility both in speech and in writing. Cattell found that of all of the objective tests developed for assessing temperament, the fluency tests were the most valid for testing surgency. Studman had also come to similar conclusions.