Collective induction: Effects of multiple hypotheses and multiple evidence in two problem domains.

This article proposes that collective induction is improved more by multiple evidence than by multiple hypotheses. In Experiment 1, 4-person cooperative groups solved rule induction problems. In 9 conditions, they proposed 1, 2, or 4 hypotheses and selected evidence on 1, 2, or 4 arrays, on each trial. Correct hypotheses increased with multiple evidence but not with multiple hypotheses. Conversely, nonplausible hypotheses increased with multiple hypotheses but not with multiple evidence. In Experiment 2, 4-person cooperative groups solved a random mapping of the letters A-J to the numbers 0-9. On each trial, they proposed 1 or 2 equations in letters (e.g., A + D = ?), learned the answer in letters (e.g., A + D = G), and proposed 1 or 2 hypotheses (e.g., A = 5). Performance was improved by multiple equations (evidence) but not by multiple hypotheses.