Interpersonal comparison versus persuasive argumentation: A more direct test of alternative explanations for group-induced shifts in individual choice

One class of theories explains group induced shifts in individual choice in terms of interpersonal comparison process. By comparing himself with others a member finds out that his position is uncomfortably discrepant, e.g., he is overly "cautious" or overly "risky". Knowledge of this discrepancy presumably is necessary and sufficient to induce him to change his initial choice. Another class of theories holds that merely knowing one is different from others is unimportant. Shifts in choice occur because during discussion a member is exposed to persuasive arguments which prior to discussion were not available to him. Thus, if in a factorial design one independently varied (a) the number of others' choices available for comparison and (b) the number of arguments others presented in support of these choices, interpersonal comparison theories would predict the magnitude of the shift to be a function of (a) and not of (b), while theories of persuasive argumentation would predict the opposite. When such an experiment was performed the only reliable main effects were based on the number of arguments, (b), as predicted by persuasive arguments. In no instance did effects involving (a) approach significance.