It’s usually women who complain about being judged on appearance instead of accomplishments, but pity poor Mitt Romney, a man who apparently suffers from looking too good. MSNBC’s Chris Matthews said Romney “has the perfect chin, the perfect hair.” The cover of Time magazine said: “Sure, he looks like a president” but . . . And on “60 Minutes,” Mike Wallace kidded him for being “matinee Mitt.”

And thus facial — not racial — stereotyping reared its ugly head in the 2008 presidential election.

We almost never talk out loud about physiognomy, the bogus science of judging character on the basis of facial features. But we all do it. We like or dislike people, hire and sometimes fire them, steer them onto the fast track or nudge them into the oubliette based in part on facial prejudices of which we are scarcely even aware.

Research on facial stereotyping suggests, for instance, that — kidding from envious journalists aside — Mr. Romney stands a better chance in the G.O.P. presidential primaries because he has the look of a mature leader, with that high forehead towering over deep-set eyes and a strong (O.K., perfect) chin. And John Edwards may be at a disadvantage among Democrats because those chubby cheeks make him look just a little too boyishly winsome.

We make these kinds of unconscious judgments because our biology has prepared us to connect certain facial expressions with specific emotions. And then we over-generalize: Because the lips swell during sexual excitement, for instance, we act as if full-lipped people constantly flutter on the cusp of passion (think of President William Clinton). And thin-lipped people wear out their mattresses only by leaning on them during bedtime prayers (think of President George H.W. Bush).

Similarly, we have evolved as mammals to coo over a baby face. It’s how nature tricks us into taking care of our offspring. When baby-faced features carry over into adulthood, our innate response carries over, too. So Mr. Edwards may well inspire more warmth and trust than someone with a severe brow.

But will that help get him elected?

It may merely make him easier to forgive when he goes wrong. In one study tracking more than 500 cases of intentional wrongdoing in Boston small-claims court, judgments went against mature-faced defendants 92 percent of the time, but against baby-faced defendants only 45 percent of the time. The perception, says Brandeis University psychologist Leslie Zebrowitz, is that “baby-faced people are too honest and naïve to have a high probability of committing a premeditated offense.”

When it comes to choosing leaders, on the other hand, we often opt for people who look the part. For instance, another study categorized graduates in the West Point class of 1950 according to whether their faces looked dominant or submissive. Predictably, the top rank of general overwhelmingly went to people who fit the “tough warrior” stereotype. The people making such promotions apparently treated this facial type as a reliable indicator of the ability to command. And maybe there was method in their madness: Being sent off to war by a leader who looks like Howdy Doody might well be demoralizing.

Businesses still often act as if the stereotypical markings of executive style are a prerequisite for promotion. At a veterinary medicine company not long ago, a vice president got hired in part because he had, no kidding, “managerial eyebrows.”

Apart from the tendency to lead us into utterly superficial snap judgments, there is a darker side to facial stereotyping. Ugly people get overlooked. (They “develop complexes due to the humiliation and abuse they endure over the years,” one executive told me, to justify not hiring them.) Meanwhile handsome people often enjoy the unfair advantage of the “attractiveness halo.”

And one prejudice may shade into another. Abercrombie & Fitch paid $40 million a few years ago to settle a lawsuit alleging that it staffed its stores with hip, attractive young people — who happened disproportionately to be white.

“Looking the part” for leadership also frequently means looking male. People seem to prefer masculine-looking leaders even, weirdly, when all the potential candidates are women. In one study, test subjects considered only female candidates for a leadership position. But they gave their top rating to the candidate with a biologically masculine face and a masculine style of dress.

Being aware of our facial stereotypes is a way to avoid being victimized by them. A feminine-looking candidate can improve her chances by switching to a masculine style of dress — a lesson Hillary Clinton has plainly taken to heart. Changing behavior or facial expression can also help a candidate escape a facial stereotype. Smiling, for instance, might take the edge off Mr. Romney’s “too handsome” problem, or Rudy Giuliani’s prosecutorial scowl. Mr. Edwards, on the other hand, might want to smile a bit less.

None of this is likely to determine the outcome of this presidential election. Looking handsome and mature didn’t help another Massachusetts candidate in the last one. But it suggests a useful strategy if you want to get past your own superficial judgments during the next big presidential debate:

Just close your eyes and listen to what they say.