Invisible forces that control our behavior have inspired our best story­tellers, from Euripides to Steven Spielberg. Whether we’re yanked around by jealous gods, Oedipal urges or poltergeists, the idea that we feel powerless to direct our own actions has a visceral appeal, one exploited by Shankar Vedantam in “The Hidden Brain,” his exploration of the unconscious mind.

Most previous popular treatments of subliminal forces haven’t been data driven. Vedantam, who until recently wrote the Department of Human Behavior column for The Washington Post, hopes to fill that gap. His entertaining romp through covert influences on human behavior began as a series of columns, and true to its genesis, it reads as vivid reportage overlaid with a sampling of science. Ranging widely from the role of social conformity in violence to snapshots of racial and gender prejudice, Vedantam draws expansive arcs between findings from social psychology and the nation’s sensibilities and voting patterns. “Unconscious bias reaches into every corner of your life,” he writes, thanks to a “hidden brain” generally inaccessible through introspection. As with crop circles, all we see are the traces left by covert attitudes, never the perp at the scene of the crime.

Colorful characters form the backbone of the narrative; we meet a bickering, long-married academic couple, a rapist with great teeth, a woman working the night shift at a tire factory, a woman suffering from a rare form of dementia and a cult member. What binds this motley crew together? All are victims of some form of irrationality — those imperceptible forces that often prompt our actions in the real world, the ones that are at odds with our ideals.

Image Credit... Illustration by Dan Page

Most of us assume that honesty and generosity are personality traits polished over a lifetime of social interaction. But Vedantam shows how imperceptible social signals determine, for example, how deeply you’ll dig into your pocket. In offices with an honor system for coffee, people are more likely to pay on days when a photograph of human eyes is discreetly posted above the coffee machine, according to one British study. They’re more prone to cheat if a still life of daisies is pasted there instead — even if they say they’re unaware of either picture. Another experiment demonstrates that you’re likely to give a handsome tip to a waiter who repeats your food order verbatim. In fact, you’ll tip an average of 140 percent more than you would if he just paraphrases it. It’s all about social mimicry, apparently, our hidden ability to sync our behavior with the group’s.