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Modern slot machines are fascinating devices. Most are electronic, not mechanical, which means that you pull the lever (or press a button) and the machine draws a random number which determines whether you have won. After that, the machine displays a show on the screen which ultimately lets you see whether you have won.

The last time I was in Las Vegas, I watched people playing the slots with interest. Often, they would pull the lever and the wheels would line up so that they seemingly almost won a big prize, but did not.

Why was the machine set up so that it looked as if people nearly won?

This issue was explored in a paper in the June 2015 issue of Psychological Science by Monica Wadhwa and JeeHye Kim. They were interested in how near misses affected our pursuit of another, unrelated goal.

In many of their studies, they used a clever manipulation: Participants were asked to test out a new video app in which they uncovered squares in a grid. If they uncovered all diamonds, they would win. Participants testing the app would also get a small prize if they uncovered eight diamonds in a row. In clear loss condition, participants uncovered only one diamond. In a near miss condition, they uncovered seven diamonds, but then got a rock in the eighth position trial. In a far miss, they also uncovered 7 diamonds, but they got a rock in the second position, so they knew they had lost early on.

In one study, after trying out the game, participants had to walk to a far table to pick up a chocolate bar as a gift for participating. And participants walked faster to get the chocolate bar if they had had a near miss than if they did not.

In a second study, participants saw pictures of either large amounts or small amounts of money after playing the game. The authors then measured how much they salivated. Salivation is a measure of how much people want something—even when it isn’t food. When participants had had a near miss, they salivated more over large amounts of money than over small amounts of money. But there was no difference in salivation—and very little salivation overall—when participants lost immediately.

In a field experiment, participants were approached right before entering a store where they could buy fashion accessories. They were given a scratch-off lottery ticket, and were asked to scratch off the spaces on the ticket in order. The tickets were designed so that participants had a near miss, won the prize, or lost early. After scratching off the ticket, participants went shopping. Afterward, the researchers obtained participants' receipts from their shopping trips. Participants in the near miss condition spent more money overall than those in the clear loss or the win conditions. The near miss seems to have energized people to achieve their .

Source: Wikimedia Commons, Jeff Kubina

This research fits with a lot of work suggesting that people are most motivated when they have not yet achieved their goals, but still feel those goals are attainable. A near miss creates exactly those circumstances: The goal seems completely in reach but then it is not achieved. The motivational energy people get from this situation has to be spent in some way, and so people apply that energy to the next goal they engage.