Confidence in expectations: A test of the triangle hypothesis

Kelley and Stahelski's (1970) triangle hypothesis states that competitors hold homogeneous views of others by assuming that most others are competitive, whereas cooperators or pro‐social people hold more heterogeneous views by assuming that others are either cooperative or competitive. To evaluate the triangle hypothesis, this study examines differences between pro‐socials, individualists, and competitors not only in their expectations about others' choice behaviour, but also in the confidence with which such expectations are held. It was found that pro‐social subjects expected more cooperation than individualists and competitors. More importantly, as predicted on the basis of the triangle hypothesis, pro‐socials were less confident about their expectations than competitors, with individualists holding intermediate levels of confidence.