Source: Dan Zen - Flickr: Ava Surprised. Licensed under CC BY 2.0 via Wikimedia Commons

We have all experienced surprise. Some of those surprises are wonderful. You get home and find an unexpected gift waiting for you. That is a happy surprise. Perhaps though, you turn on the news and find out that a young actor you admire has died. Again, you experience surprise, but this time the emotion is negative.

Psychologists have explored what lies at the root of the feeling of surprise. In particular, we know that surprise comes in degrees. If you wake up in the morning at your usual time, get dressed and leave the house, then nothing is surprising at all. If you wake up in the morning to find that your alarm clock did not go off and you are late for work, you might be very surprised. But, if you went to sleep the night before knowing that there were going to be thunderstorms overnight and then you wake up late because your alarm did not go off, you are surprised, but not very surprised.

What drives this feeling of surprise?

There have been two main types of explanations. One focuses on probability. The idea is that when things are unexpected because they don’t happen often, they are surprising. The second idea is that explanation matters. The degree of surprise people experience depends on how easily they can explain what happened.

An extensive paper by Meadhbh Foster and Mark Keane in the August 2015 issue of Cognitive Psychology explores the influence of ease of explanation on surprise.

As a simple demonstration, the first experiment looked at surprising events that are either familiar or unfamiliar. A story about a woman going to the ATM and taking out money and later finding that her wallet was missing from her handbag is a more familiar story than one about an angry man who goes to his boss’s office intending to quit and gives his boss a hug. People expressed more surprise at the unfamiliar scenario than the familiar one.

A second study then manipulated ease of explanation by varying whether a partial explanation was included in the scenario. The scenario about the woman with the missing handbag might include the detail that her handbag was open. The scenario about the man going to his boss might include the detail that he was offered a promotion. People given this partial explanation found the situation less surprising than those not given the partial explanation both for familiar and unfamiliar situations.

Another study in this series did an interesting manipulation. If surprise reflects people’s judgments about the difficulty of generating explanations, then asking people to generate three different explanations for an event should be harder than generating one, and so people asked to generate three explanations should actually be more surprised at an event than those asked to generate only one. This finding was obtained, though only for the familiar stories. The unfamiliar stories were so surprising already it was hard to make them seem more surprising.

A final study manipulated ease of explanation in a different way. For each scenario, a hint was given that would either make an explanation fairly easy to generate or hard to generate. In a scenario about bumping into a friend in a foreign country, participants might receive the hint copycat (which suggests the explanation that the friend copied the plan) or circus (which does not suggest an obvious explanation). Another scenario involved seeing a rhino at a coffee shop (in which case circus prompts an explanation, but copycat does not). When given a prompt that suggests an explanation, people found the scenarios less surprising than when given a prompt that did not suggest an explanation.

An interesting facet of this study is that some participants were asked to judge the probability of the event. The prompt did not influence people’s judgments of how probable it would be to experience these events. So, the judgments of surprise seem to be related to the ability to explain them rather than the low probability of the surprising events.

This finding suggests that surprise has value, because it serves as a signal of how much work someone will need to do to understand what has just happened. For very surprising situation, a person will need to set aside time to really figure out what is going on. Having an emotional marker of this difficulty is useful, because it signals that someone needs to devote time to making sense of the world. And, because surprise tends to make people stop what they are doing, it clears some mental space for doing that work.

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