“The hypothesis is that there’s a sweet spot between too much fear and not enough fear, between predictability and unpredictability, where you feel you have a certain amount of control over the situation, but there’s still a degree of unpredictability,” [researcher Mathias] Clasen told Ars last year. And the results largely support that hypothesis. When Clasen’s team plotted the relationship between levels of self-reported fear and enjoyment by participants in [a haunted house], the data showed an inverted U-shape—a Goldilocks zone for maximum enjoyment. There was a similar U-shaped trend in the data for participants’ heart-rate signatures.
“This is strikingly similar to what scientists have found to characterize human play,” said [researcher Marc Malmdorf] Andersen. “We know, for instance, that curiosity is often aroused when individuals have their expectations violated to a just-right degree, and several accounts of play stress the importance of just-right doses of uncertainty and surprise for explaining why play feels enjoyable.”