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Why do people seem to make some decisions slowly and but other decisions are made quickly? You might speculate that if the decision is something small and insignificant, like what to order at a restaurant, they will make the decision quickly, but if they’re deciding something large and important, like whether or not to move to a new apartment or a new city it will take a long time to decide. It seems natural to assume that important decisions would take more time.

But in reality, the importance of the decision isn’t what causes people to make up their minds quickly or slowly.

How about individual personality? Some people are spontaneous and others take a long time to decide everything. Although there are differences in personality (and brain chemistry) that cause some people to be more impulsive than others, even impulsive people sometimes take a long time to make decisions, and cautious people occasionally decide on things quickly. So it’s not individual personality that predicts the time required to make a decision.

The best predictor of when people are going to make a decision is how confident they are that they are making the best decision. And what’s interesting is what affects that confidence.

The Effects Of Evidence And Elapsed Time

People make decisions when they’re confident that they’re making the “right decision.” If they’re not confident about their incoming information, then they won’t make that “go” decision.

If people make decisions when they reach a certain level of certainty, the next question is what brings them to that moment of certainty? If your design is supposed to encourage people to make a decision (click on the Register button, download a file, press the Buy button), is there anything you can do to help people feel more certain and therefore speed up the decision-making process?

Research by Roozbeh Kiani (2014) investigated the relationship between certainty, elapsed time, and the amount of evidence.

When people are considering a decision, their brain networks (largely unconsciously) are not only analyzing all the factors and assessing the pros and cons of the decision, but also assessing how certain they are of making a decision at that point and how certain they are that the decision they’re making is the best one. How do these decision-making brain networks decide if a person is certain? They use the person’s past accuracy on decisions like this, and add to that information all the evidence, both pro and con, that the person has been accumulating for this particular decision.

Kiani specifically studied the effect that elapsed time has on the feeling of certainty. As time drags on and a person hasn’t made a decision, the parts of the brain that are involved in decision-making start to wonder if the person is taking a long time because the decision is difficult. The more time it takes, the more the network decides this must be a difficult decision. And if the decision is difficult, then the decision network becomes less certain that the person will make a good decision and that the person is ready to decide. Which of course puts the person into a loop (the longer it takes, the more difficult it must be and the less certain the person is, and therefore it takes more time).


  • People will not make a decision until and unless they feel confident of the decision.
  • This confidence factor is true for any type of decision, large or small.


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