particularly gratifying to see a puffed-up peasant-driver fall from grace...,

NYTimes | The world’s highest-paid athlete began his spectacular downfall by crashing a Cadillac S.U.V. into a fire hydrant and a tree. Initial accounts of Tiger Woods’s 2009 accident reported that his wife had broken the vehicle’s window with a golf club to free him, but when word spread that the couple had been fighting over allegations of his infidelity, the smashed window became a metaphor for his shattered reputation. 

As the scandal unfolded, the sports celebrity who had built an empire on his image as an upstanding family man was revealed as a glutton for extramarital sex and an author of tawdry texts to mistresses and paid escorts. Almost overnight, Mr. Woods became a target of ridicule, not to mention a website and a Twitter account with the sole purpose of propagating jokes about him. 

The wicked delight over that turn of events has a German name so apt we’ve adopted it in English. Schadenfreude, or “harm-joy,” is the pleasure derived from another’s misfortune, and Richard H. Smith, a University of Kentucky psychology professor, has built a career around studying it and other social emotions. He previously edited an anthology about envy, a close sibling to schadenfreude. 

As perverse as the emotion may seem, it serves an adaptive function, Dr. Smith argues in this enjoyable book. It stems from social comparisons, which allow us to assess our talents and determine our status in the social order. The urge to make these comparisons appears hard-wired — studies show that even monkeys and dogs measure themselves against their peers. 

Schadenfreude provides a glimpse into what the psychologists Roy F. Baumeister and Brad J. Bushman have called “the most basic conflict in the human psyche” — the friction between our selfish impulses and self-control. “We are all savages inside,” the author Cheryl Strayed wrote in her Dear Sugar column at the website The Rumpus. “We all want to be the chosen, the beloved, the esteemed.” 

But life doesn’t always turn out that way, and when we encounter someone who is more chosen, beloved or esteemed than we are, our natural instinct is to tear them down to our level. If this illicit desire is fulfilled by happenstance, schadenfreude ensues. Clive James captured the feeling in a poem that takes its title from its first line: “The book of my enemy has been remaindered/ And I am pleased.” 

When envy invokes pain, schadenfreude provides a potent antidote. Mr. Woods’s success on the golf course and seemingly perfect life — beautiful wife, family and flawless reputation — “provided an acute contrast for most people, even if they were not interested in golf,” Dr. Smith writes. Though some people were surely inspired by him, perhaps more felt diminished. His downfall brought him closer to their level, and thus allowed his enviers to feel better about themselves. 

The 17th-century philosopher Thomas Hobbes proposed that humor often arose from a sudden sense of superiority, and Dr. Smith writes that our culture thrives on downward comparisons that provide this “sudden glory.” 

“Do we watch reality television for precious insights into the human condition?” he asks. “Please. We watch for those awkward scenes that make us feel a smidgen better about our own little unfilmed lives.”