The book examines how individual differences in candidates' levels of extraversion interact with facets which have been shown to affect scores obtained on oral performance tests. Three major studies are presented: the first is concerned with the individual candidate in the model; the second study investigates the role of the rater in the oral test process; the final study is concerned with the degree of interactivity required of pairs of candidates, each of whom also acts as an interlocutor in the performance of an oral test task. Results of the studies confirm that when an appropriate instrument is used to assess personality, and when theoretically sound hypotheses derived from the psychological literature are tested, significant differences can be observed in the responses of introverts and extraverts on particular oral test tasks.