Individual-group (I1,G) and pre-post-discussion individual (I1I2) choice shifts were investigated. Individuals worked alone, then in interacting groups, and then alone again to select grading schemes for courses in which they were enrolled. They made choices from a set of defined options which were shown to differ significantly in perceived risk. Group size, heterogeneity of group members' prediscussion decisions, and time of decision task administration were statistically controlled. I1G choice shift was investigated for 1353 students who formed 268 groups. I1I2 choice shift was investigated for 330 students in 65 groups. For both I1G and I1I2 choice shift we found significant independent effects supporting cautious shift and simple averaging. The effect sizes of caution and averaging were not significantly different from each other. Additional participants, who were members of groups experiencing choice shift, provided information as to why the shifts occurred. A content analysis of their responses revealed that two-thirds provided explanations consistent with persuasive arguments theory and one-third provided explanations consistent with social comparison theory. © 1992.