Yarczower, M., Kilbride, J. E., & Hill, L. A. (1979). Imitation and inhibition of facial expression. Developmental Psychology, 15(4), 453-454.
http://dx.doi.org/10.1037/0012-1649.15.4.453
Seven 1st graders, 8 6th graders, and 8 college students were asked to imitate facial expressions depicted in photographs when they were alone and when someone else was present. Accuracy of imitation and intensity of facial expressions in the older children but not in the younger children were suppressed when someone was present. Also, the more intense facial expressions were suppressed more than the less intense expressions. Data are consistent with the proposition that socialization training yields a susceptibility to social inhibition of imitated facial expressions. (3 ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)