Women adjusted their eating patterns to match those of their dining companions, researchers found.
In a small study, young women were significantly more likely to take a bite when the person with whom they were sharing a meal drew her fork to her mouth (P<0.001), Roel Hermans, PhD, of Radboud University Nijmegen in the Netherlands, and colleagues reported online in PLoS One.
The finding suggests that behavioral mimicry -- the process by which people unwittingly imitate the behavior of another person -- may be at work during dinner.
Studies have shown that women eat more when the people they're dining with eat more, and tone down their consumption when their partners eat less. It's been hypothesized that behavioral mimicry was responsible for the behavior, but no studies had yet tested whether that's the case.
So Hermans and colleagues assessed 70 pairs of young women, mean age 21, who had dinner together in the "bar laboratory," a replica of a real bar at the investigators' institution.
One of the women in the pair had previously been instructed by an investigator as to how much food they should eat: a small, medium, or large amount of the small or medium portions provided to them -- making for a total of six different eating conditions.
Their dining partners weren't given any instructions on how much they should consume.
A bite was classified as mimicry if it occurred within five seconds of the partner's bite. Over the course of the study, a total of 3,888 bites were taken -- the instructed eaters took about 30 bites, while the unwitting eaters took about 41 (P<0.001).
Hermans and colleagues found that the women indeed mimicked each other's eating behavior; they were significantly more likely to take a bite when their partners did, compared with when they did not (P<0.001).
They also saw that the unwitting eaters were more likely to mimic their partners' bites than vice versa (P<0.001), and mimicry was stronger during the beginning of the meal: women were more than three times as likely to mimic bites at the outset as they were at the end (P<0.05).
The findings were no different when controlling for body mass index (BMI), though the researchers noted that the sample consisted mostly of normal-weight participants.
They concluded that the findings "fall within the typical definition of behavioral mimicry" -- watching a dining companion take a bite might activate the motor system to make the same move, they wrote.
On the other hand, the women may have been actively monitoring each others' eating habits to maintain a similar eating pattern, in an effort to ensure they ate an "appropriate" amount -- though the researchers noted that the study didn't assess which was the case.
With regard to the synchrony falling off at the end of the study, the researchers said it's possible that the tendency to ingratiate oneself with an eating companion may be more marked at the beginning of meal, thus leading to more mimicry, but further study is needed.
More work also is needed on the interactions between other groups such as children and adolescents, and on how much mimicry occurs between people who are acquainted with each other, such as family and friends, they said.
The study was supported by the Behavioral Science Institute of the Radboud University Nijmegen.
The researchers reported no conflicts of interest.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner