From Adam Alter’s Irresistible: Why We Can’t Stop Checking, Scrolling, Clicking and Watching:
Juice refers to the layer of surface feedback that sits above the game’s rules. It isn’t essential to the game, but it’s essential to the game’s success. Without juice, the same game loses its charm. Think of candies replaced by gray bricks and none of the reinforcing sights and sounds that make the game fun. ...
Juice is effective in part because it triggers very primitive parts of the brain. To show this, Michael Barrus and Catharine Winstanley, psychologists at the University of British Columbia, created a “rat casino.” The rats in the experiment gambled for delicious sugar pellets by pushing their noses through one of four small holes. Some of the holes were low-risk options with small rewards. One, for example, produced one sugar pellet 90 percent of the time, but punished the rat 10 percent of the time by forcing him to wait five seconds before the casino would respond to his next nose poke. (Rats are impatient, so even small waits register as punishments.) Other holes were high-risk options with larger rewards. The riskiest hole produced four pellets, but only 40 percent of the time—on 60 percent of trials, the rat was forced to wait in time-out for forty seconds, a relative eternity.
Most of the time, rats tend to be risk-averse, preferring the low-risk options with small payouts. But that approach changed completely for rats who played in a casino with rewarding tones and flashing lights. Those rats were far more risk-seeking, spurred on by the double-promise of sugar pellets and reinforcing signals. Like human gamblers, they were sucked in by juice. “I was surprised, not that it worked, but how well it worked,” Barrus said. “We expected that adding these stimulating cues would have an effect. But we didn’t realize that it would shift decision making so much.”
I’ll post some other thoughts on the book later this week.