Tomasso DeRosa-US PRESSWIRE/Corbis

Previous research has found that people who generally have more positive emotions tend to experience a broad range of benefits—more stable marriages, better social skills and just greater happiness overall—compared with those who are more dominated by negative emotions. One measurement that researchers use when assessing emotions is smile intensity, based on the premise that the authenticity of your grin conveys the depth of your positive emotions. In a study recently published in the journal Psychological Science researchers from Wayne State University analyzed the smiles of 230 Major League Baseball players from the 1952 player register to determine how positive emotions influence longevity. By blowing up images from player cards, researchers assessed player smiles—categorizing them as “no smile,” “partial smile” and what is known as a “Duchenne smile,” or the authentic, spontaneous expression of happiness named for a 19th century French neurologist. They found that, players who had more authentic smiles—conveying a deeper level of contentment—were more likely to live longer than those who were only partially smiling, or not grinning at all.

Of the Major League players who had died before June 2009, longevity varied in keeping with happiness, as indicated by their smile intensity back in 1952: players with no smiles lived an average 72.9 years; those with partial smiles lived an average of 75 years; and those with big, authentic grins lived an average of 79.9 years, the researchers found.

Based on the data available researchers couldn’t confirm whether players were prompted to smile by the photographer, or if they did so spontaneously. Yet, the researchers write, this isn’t necessarily problematic as “the fact that relatively few individuals had full Duchenne smiles indicates that even if smiles were requested, smile intensity reflected a general underlying disposition.” They continue that, if, as previous research suggests, the emotion conveyed in expressions is truly indicative of contentment, “individuals whose underlying emotional disposition is reflected in voluntary or involuntary Duchenne smiles may be basically happier than those with less intense smiles, and hence more predisposed to benefit from the effects of positive emotionality.”