Explaining is not enough: Appealing explanations should also be surprising.

Philosophers have attempted to define the features that make an explanation a good explanation, and psychologists have shown that people are sensitive to many of these features. Psychologists have also pointed out the importance of the phenomenology of explanations: the pleasure we derive from formulating or encountering good explanations would motivate us to seek more explanations. However, it seems that many good explanations do not trigger such positive feelings: they are good explanations, but they are not particularly appealing. We suggest that for an explanation to be appealing, it should not only explain the relevant phenomenon (be explanatory), but it should also be surprising. This is what we observe in three experiments, using both explanations from past studies, and more ecologically valid explanations gathered on the subreddit Explain Like I'm Five. We also find that the usefulness of the phenomenon being explained is another predictor of the appeal of the explanation. Finally, we show that surprisingness ratings do not depend only on whether the explanation was already known, and that their effect on appeal does not decrease when controlling for prior knowledge. Instead, explanations are judged more surprising when others do not know them, and we hypothesize that internal properties of explanations also play a role.