Did you catch that guy’s smile?  Probably.  We are able to accurately recognize a smile in about 50 milliseconds (that’s a fleeting 1/20 of a second).  Not only that, we can recognize a happy expression on someone who is standing half a football field away. 

In a recent article in Current Directions in Psychological Science, Vaughn Becker and Narayanan Srinivasan review a number of fascinating findings on the vividness of the happy face.  In some of their own research, Becker and Srinivasan have shown people pictures of faces that start out neutral and then turn either happy or angry.  Observers are able to detect the change to happiness more quickly even than the change to anger (which is something our ancestors would not have wanted to miss).  And happy faces jumped out even when they were blurred or had color information removed (see figure 1).

Figure 1

In another study, Srinivasan and Gupta asked people to search for letters on backgrounds that contained faces bearing either neutral, sad, or happy expressions (the facial expression was irrelevant to their main task, which was to hunt out particular letters).  When later asked if they remembered the faces, people were not very good at remembering either sad or neutral faces.  However, the incidental happy face was more than twice as likely to engrave itself into their memory stores (see figure 2).

Figure 2: Srinivasan Gupta results

Why are we so good at noticing and remembering happy faces?  Becker and Srinivasan speculate that the ability to recognize happy faces was probably quite important to our ancestors.  They note Hager and Ekman’s argument that, by being able to detect a happy face coming from half a football field’s distance, one can avoid throwing a spear at someone who is approaching the village with peaceful intentions (and this of course allows one to consequently avoid unnecessary warfare with the fellow's relatives from down the river, besides being able to trade with him for a fishing net or a tasty squirrel). 

Douglas Kenrick is author of The rational animal: How evolution made us smarter than we think.  and of Sex, Murder, and the Meaning of Life:A psychologist investigates how evolution, cognition, and complexity are revolutionizing our view of human nature.

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References:

Becker, D. V., & Srinivasan, N. (2014). The Vividness of the Happy Face. Current Directions in Psychological Science, 23(3), 189-194.

Becker, D. V., Kenrick, D. T., Neuberg, S. L., Blackwell, K. C., & Smith, D. M. (2007). The confounded nature of angry men and happy women. Journal of personality and social psychology, 92(2), 179-190.

Becker, D. V., Neel, R., Srinivasan, N., Neufeld, S., Kumar, D., & Fouse, S. (2012). The vividness of happiness in dynamic facial displays of emotion. PLoS ONE, 7(1), e26551.

Hager, J. C., & Ekman, P. (1979). Long-distance transmission of facial affect signals. Ethology and Sociobiology, 1, 77–82.

Srinivasan, N., & Gupta, R. (2010). Emotion-attention interactions in recognition memory for distractor faces. Emotion, 10, 207–215.

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