Consider an experiment economists call “the ultimatum game”: The experimenter gives one player, the sender, $20 to distribute between himself and another player, the receiver. An egalitarian sender might propose a split of $10 each. A more selfish sender might propose to give the receiver only $1, keeping $19 for himself. If the receiver accepts the deal, the two players collect their shares. If the receiver rejects the deal, both walk away with nothing. Were humans perfectly rational, the receiver would accept whatever is offered: even a dollar is better than nothing, right? Instead, researchers find, receivers will reject an overly lopsided deal, gladly giving up their shares just to punish the stingy senders.

In “The Upside of Irrationality,” Dan Ariely, a professor at Duke, gives us a tour of the irrational side of human decision-making and the science of behavioral economics. When it comes to our motivations, he writes, we are less like “hyper-rational Mr. Spock” and more like the “fallible, myopic, vindictive, emotional, biased Homer Simpson.” Given these frailties, Ariely wants to help us “figure out how we can get the most good and least bad out of ourselves” when making choices about our money, our relationships and our happiness.

Image Dan Ariely Credit... Courtesy of Dan Ariely

As in his previous book, the best-selling “Predictably Irrational,” the experiments Ariely describes generate entertaining and often counterintuitive insights. We learn, for example, why it’s better not to reward yourself with breaks from the grind of doing your ­taxes — and why it is a good idea to leave the hot tub to stand shivering for a bit before jumping back in. (Interruptions, studies have shown, prevent us from adapting to an experience, thereby heightening pleasure but also exacerbating pain.) Those still reeling from the audacity of Goldman Sachs will particularly enjoy the chapter on why outsize bonuses may actually reduce the quality of an executive’s performance.