Laetitia Barthomeuf and her team presented 43 5-year-olds, 38 8-year-olds and 42 adults with photographs of two women eating various foods. As they ate, the women either looked happy, disgusted or just had a neutral expression. There were six different foods - three that the participants had earlier said they liked (chocolate, bread and cream cake) and three that they said they disliked (kidney, black pudding, cooked sausage with vegetables). Twenty-seven additional participants had been excluded earlier because their preferences didn't fit this pattern.

As they looked at each photo, the child and adult participants were asked to say how much, on a scale of 1 to 10, they desired to eat the food that the woman in the photo was eating. The take home finding - the children, especially the five-year-olds, were influenced much more by the facial expressions of the women, than were the adults.

If the woman in the photo had a look of disgust, this reduced the children's, and to a lesser extent, the adults', desire to eat foods that they liked. In contrast, if the woman had a look of pleasure on her face, this  increased the children's, and to a lesser extent, the adults', desire to eat foods they didn't like (for five-year-olds only, it also increased their desire to eat foods they liked). Even a neutral facial expression in the eating women made a difference - increasing and decreasing the participants' desire for liked and disliked foods, respectively, especially in the children.

The researchers speculated that the influence of the women's facial expressions occurred because seeing their expressions led to simulations of those same emotions in the minds of the participants. They further suggested that this process is accentuated in younger children because of the immaturity of their prefrontal cortex.

The study has some obvious weaknesses, acknowledged by the researchers - they didn't measure actual eating behaviour, and the stimuli were photos, as opposed to a real-life dining situation. Nonetheless, they predicted the effects of other people's emotional expressions might be even larger in a more realistic situation and that the results therefore have important implications for the encouragement of children's healthy eating habits. "Adults may unconsciously influence children's food preferences via their facial expressions of pleasure or disgust," they said.
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Barthomeuf, L., Droit-Volet, S., and Rousset, S. (2012). How emotions expressed by adults’ faces affect the desire to eat liked and disliked foods in children compared to adults. British Journal of Developmental Psychology, 30 (2), 253-266 DOI: http://dx.doi.org/10.1111/j.2044-835X.2011.02033.x 

From BPS Research Digest