Educational seduction, in which a charismatic, entertaining instructor obtains favorable student ratings while presenting insufficient lecture content, threatens the validity of student ratings and teaching effectiveness research. To examine the effects of one educational seduction variable, instructor expressiveness, on student achievement attributions and affective reactions, four studies (2 in 1980-81; 2 in 1981-82) were conducted, in which 532, 229, 220, and 165 male and female college students viewed two 25-minute videotaped lectures, manipulated for high or low instructor expressiveness. Subsequently, the students took an achievement test on the material and completed two profiles assessing attributions, achievement responsibility, and emotional response. An analysis of the results showed that instructor expressiveness had a consistent and moderate to large effect on student achievement across all four studies. The high expressive instructor produced a greater internal mastery orientation in students and enhanced students' confidence in their performance. The findings raise important questions about whether expressiveness affects other cognitive processes such as expectations or motivation. (BL)