How many hindsight biases are there?

The answer is three: questioning a conceptual default assumption in hindsight bias research, we argue that the hindsight bias is not a unitary phenomenon but consists of three separable and partially independent subphenomena or components, namely, memory distortions, impressions of foreseeability and impressions of necessity. Following a detailed conceptual analysis including a systematic survey of hindsight characterizations in the published literature, we investigated these hindsight components in the context of political elections. We present evidence from three empirical studies that impressions of foreseeability and memory distortions (1) show hindsight effects that typically differ in magnitude and sometimes even in direction, (2) are essentially uncorrelated, and (3) are differentially influenced by extraneous variables. A fourth study found similar dissociations between memory distortions and impressions of necessity. All four studies thus provide support for a separate components view of the hindsight bias. An important consequence of such a view is that apparent contradictions in research findings as well as in theoretical explanations (e.g., cognitive vs. social-motivational) might be alleviated by taking differences between components into account. We also suggest conditions under which the components diverge or converge.