The posed stare-down is a staple of the pre-fight ritual. Two fighters, one day removed from attempting to beat the memories from each other, stand impossibly close, raise their clenched fists and fix their gaze on the other’s eyes as cameras click away. This has always seemed little more than a vehicle for media hype, but new research from psychologists at the University of Illinois suggests that there may be clues in this bit of theatre that predict the results of the fight to come.

Specifically, the researchers hypothesized that there’s something about the fighters’ facial expressions in this standoff that reveal the competitive dynamics between them. A subtle, and perhaps unintentional, communication of submission from one fighter to the other. A recognition of the opponent’s power. The smile.

Facial expressions have long been thought to be reliable indicators of a person’s true feelings. Indeed, in his book “The Expression of the Emotions in Man and Animals” Darwin suggested that such expressions have evolved precisely because they serve this important function. The smile has attracted much empirical attention and has generally been interpreted as a signal of an individuals’ immediate, as well as long-term, well-being. In a particularly interesting study, the frequency and “authenticity” of smiles in high school yearbook photos tended to predict higher levels of subjective well-being years later.

But smiles can mean different things in different contexts. The researchers here were particularly interested in what a smile might mean when displayed between competitors. Instead of merely communicating a fighter’s good spirits, the researchers hypothesized that it would be a submissive signal that reveals a fighter’s reduced hostility and lower willingness to aggress towards the opponent. Prior research supports this possibility. In primates, baring teeth is used as a signal of submission or subordination – a means of avoiding potentially harmful and aggressive physical confrontations with others. In humans, another yearbook study showed that higher levels of testosterone are significantly correlated with smile intensity: the higher the testosterone, the fewer the smiles. And in a separate study people tended to smile more when they were lower in social status.

So, if a fighter knows he is outmatched then this might be revealed when he comes face-to-face with his opponent in the staredown. If he smiles, he knows he’s in trouble. Furthermore, they hypothesized, this display will predict the outcome of the fight. The smiler will be less aggressive and more likely to lose, while the opponent, fueled by the weak display, will be more aggressive and more likely to win.

To test this idea, the researchers first had trained coders rate the intensity of the smiles of 152 Mixed Martial Arts fighters in the posed pre-fight photos and then compared these ratings to objective performance statistics from the fight, retrieved from Fightmetric.com. Outcome variables such as effective striking, effective grappling, takedowns and knockouts were analyzed for both fighters.

As expected, smile intensity predicted both the outcomes of fights as well as the more detailed measures of in-fight hostility. Interestingly, the smiles predicted both reduced hostility from the smiler as well as increased hostility from his opponent. In other words, it seemed both fighters were attuned to the information being communicated in the pre-fight smile. These results held even when controlling for existing differences in skill (i.e. the betting odds of the fight) and strength (height and weight). Though don’t go drastically altering your gambling strategy just yet -the betting line still did a better job overall in predicting fights compared to just smile intensity.

To follow up this correlational data with experimental evidence, the researchers conducted a second study in which they presented participants with the same pictures used in Study 1, but this time one of the pictures was manipulated to have either a smile or a neutral expression. They then asked participants to rate the fighters along a series of personality dimensions as well as questions measuring perceived hostility, aggression and dominance. As expected, participants rated the smiling fighter as less hostile, less aggressive and less dominant. Importantly, this study suggests that the results of Study 1 were in fact attributable to the intensity of fighter’s smiles, as opposed to some other feature of their body or face.

You might interpret this as a kind of “nice guys finish last” effect. But that’s not quite right. The authors also looked at whether smile intensity in the pre-fight photos predicted dominance and outcomes in other future fights. If the smiles are just helping us separate the gentle from the aggressive, then the nice guys should be performing consistently worse than their more hostile counterparts. This was not the case. These smiles are context-specific; they reveal something about the power dynamics between only these two fighters, not something enduring about the kinds of people that these fighters are. A fighter, smiling against opponent A because he knows he is outmatched, might be stone-faced when up against the weaker opponent B (who, by extension, would in that circumstance be reduced to a grinning fool).

Though the researchers are clear that they cannot know exactly why fighters are smiling, they suspect that it is an unintentional display. It is possible, however, that fighters, and others in competitive contexts, use these kinds of submissive cues strategically to lull their opponents into a false sense of dominance. Keeping one’s enemies closer might in some circumstances be effective. But it’s clear from these data that fights are not one such circumstance. Strategic or not, smiles before the outcome of a competition has been decided are not winning ones.

Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook, a Pulitzer prize-winning journalist and regular contributor to NewYorker.com. He can be reached at garethideas AT gmail.com or Twitter @garethideas.