The last several generations of my paternal lineage were filled with crafty, unctuous souls—men who smiled too easily in conversations with strangers and women who appeared vacuously sweet but in reality could outfox the Devil. Well, perhaps that’s a bit strong. But in this genealogical mixer of traveling salesmen, reverends, nurses, and factory workers, a certain ingratiatory capacity has indeed always struck me as being an especially prominent feature of the Bering disposition.

Take my father, for example. His particular magic, which he has performed for as long as I can remember, lies in the subtle ways he responds toward people from all walks of life. Chances are, you wouldn’t recognize it happening, but soon enough he could sell you Heaven-on-a-stick if he wanted to. How? He’d do it through his rapt attention and his frequent nods to your banal stories, his laughter at your most wanting of jokes, his smiling assent to even your strangest of thoughts. In fact, throughout the 1980s and early 90s, I watched him use these tacit measures of persuasion to go from a meager salesman for Eveready Batteries to become one of the senior vice presidents at Borden, Inc.

Of course, my father isn’t always sincere in his agreeable affectations, but I suspect he isn’t entirely insincere either. Rather, for him, these nonverbal behaviors are more like a behavioral heuristic—automatically deployed because they’ve proven to be socially effective. A recent study conducted by University of California, Berkeley psychologists Michael Kraus and Dacher Keltner may explain why my paternal pedigree is synonymous with affirmative head-nods, engaging smiles, inquisitive eyebrow raises, and good-natured laughter: my immediate ancestors were mostly broke, or at least to some degree financially bereft. My father’s father was a factory man, his mother an office assistant at the same plant; theirs was a lower middleclass family that never quite lived off the dole, but which was usually only a paycheck away from such a gloomy post-Depression era prospect.

Kraus and Keltner’s study, published in last month’s issue of Psychological Science, shows that individuals who are low on traditional measures of socioeconomic status (SES) (their family earns less than the state’s median income) demonstrate more “engagement cues” in conversations than do their wealthier peers. The authors hypothesized this effect based on the following evolutionary theory:

In nonhuman species, the ability to assess resource displays accurately leads to preferred mating opportunities and the avoidance of costly, aggressive encounters in negotiations of status. In humans, nonverbal displays of the capacity to provide resources are likely to be important in mate selection, as well as in group members’ attempts to identify individuals suitable for positions of leadership.


In other words, the rich can afford to be relatively aloof in their conversational exchanges. However, those of us whose net worth is in negative equity tend to be more attentive communicative partners, since we have more to gain by being liked.  With resources aplenty, powerful people are less dependent on others, and this translates to their being more disengaged in everyday social interactions.

Although Kraus and Keltner do not articulate the evolutionary mechanics of this phenomenon very deeply, their naturalistic explanation of nonverbal behavior should not be taken to mean that such behaviors are “innate” to whatever SES milieu one happens to be born into. On the contrary, snooty rich kids probably have snooty rich parents and snooty rich friends, and at least to some degree they may have learned to mimic these behaviors. However such behaviors come about developmentally, the evolutionary interpretation accounts for why the wealthy are “disengaged” and the less wealthy “engaged” during social interactions—and not the other way around.

In their study, Kraus and Keltner asked over 100 undergraduate students to engage in a short interaction (a five-minute “get-acquainted” conversational exchange) with a complete stranger. Seated in chairs and facing each other about 3 ft apart, students were told to describe themselves to this other student, then to converse freely for the remaining five-minutes. The students were completely naïve to the purpose of the study, which was to examine their nonverbal behaviors during this brief exchange with the other person. (A hidden video camera recorded the session.) Rather, they were told that the study was about effective strategies for job interviews, and that the get-acquainted interaction was simply a warm-up for the actual study.

Later, the authors coded the get-acquainted interaction for signs of engagement cues (e.g., head nods, eyebrow raises, laughter and gazes at the partner) and disengagement cues (e.g., self-grooming, fidgeting with objects and doodling). As predicted, higher SES significantly predicted disengagement cues. The students from wealthier backgrounds were more likely than their poorer cohorts to exhibit these “rude” displays of relative indifference. (Indeed, this SES effect occurred even after controlling for participants’ gender, since women are generally more engaged listeners than men.)

What’s more, the authors asked a group of other undergraduate students to watch the tape and to make their best guess about the SES of the people shown on the video. Based only on the participants’ nonverbal behaviors in these brief videotaped exchanges, the observers were able to make better-than-chance estimates of the participants’ family income and even their mother’s level of education, an indirect measure of SES (though they were not as accurate in judging paternal education). Kraus and Keltner conclude their report by stating that, “SES imbues the briefest interactions, influencing both what people signal nonverbally and how they are perceived.”

As for me, I think I may have inherited that same mildly disingenuous blue-collar smile as my father. Having said that, unlike my dad I’m also a pecuniary numbskull, and I have a hunch these types of engagement cues might flare up in my social behaviors every time I burn a new hole in my pocket.

In this new column presented by Scientific American Mind magazine, research psychologist Jesse Bering of Queen's University Belfast ponders some of the more obscure aspects of everyday human behavior. Ever wonder why yawning is contagious, why we point with our index fingers instead of our thumbs or whether being breastfed as an infant influences your sexual preferences as an adult? Get a closer look at the latest data as “Bering in Mind” tackles these and other quirky questions about human nature. Sign up for the RSS feed and or friend Dr. Bering on Facebook and never miss an installment again.