Infant EEG asymmetry differentiates between attractive and unattractive faces

Infants prefer familiar adults (e.g. parents) to unfamiliar adults (e.g. strangers), but they also vary in which strangers they prefer. By 6-months, infants look longer at attractive than unattractive faces (e.g., Langlois et al., 1987); and by 12-months, infants show approach behaviors toward attractive strangers and withdrawal behaviors toward unattractive strangers (Langlois, Roggman, & Rieser-Danner, 1990). These preferences may be due to a mechanism referred to as cognitive averaging (e.g., Rubenstein, Kalakanis, & Langlois, 1999). Infants cognitively average face exemplars to form a face prototype. Infants likely perceive attractive faces as familiar because these faces are similar to the face prototype; and they likely perceive unattractive faces as especially novel because these face are dissimilar from the face prototype. Even young infants may be more motivated to approach attractive than unattractive faces but do not fully express this motivation due to limitations in locomotion and communication. I applied EEG asymmetry to study neural correlates of approach and withdrawal motivation in response to attractive and unattractive faces with 6- and 10-month-olds. More specifically, I measured EEG alpha power at mid-frontal regions while 39 infants viewed a series of attractive and unattractive faces. Left EEG asymmetry relates to approach motivation whereas right EEG asymmetry relates to withdrawal motivation. I predicted infants would show greater left EEG asymmetry (i.e., approach motivation) when viewing attractive faces than when viewing unattractive faces, and that 6-montholds would show even greater left asymmetry than 10-month-olds due to developmental differences in stranger wariness. Results supported the main hypothesis but not hypotheses regarding age. Infant EEG asymmetry was greater in response to attractive faces than unattractive faces suggesting that infants are more motivated to approach attractive people than unattractive people as early as 6-months. These results link visual preferences evident at 6-months to overt behaviors evident by 12-months providing additional information regarding rudiments of attractiveness stereotypes. Furthermore, this investigation supports the use of EEG asymmetry methodology to measure infant approach/withdrawal motivation, providing infant researchers one more tool to better understand how infants evaluate novel individuals in their social environment as they decide whom to approach and whom to avoid.