“…Some studies have utilized actors rather than real therapists (Fretz, Corn, Tuemmler, & Bellet, 1979; La Cross, 1975;Smith, 1972;Trout & Rosenfeld, 1980) and have relied on college students to evaluate complex constructs such as rapport (Dinges & Oetting, 1972; Karger, 1974; La Cross, 1975;Lassen, 1973). These "impression" studies have been criticized for the weakness of their external validity (Bakken, 1978; Davis, 1985; Gladstein, 1974;Myers & Myers, 1972). Wallbott (1985) has demonstrated that there are serious limitations to data based on judgments of patients' movements made by untrained observers.…”