In a study funded by the National Institute of Mental Health and Texas A&M University, researchers Jessica E. Kieras, Renée M. Tobin, William G. Graziano, and Mary K. Rothbart found that children's ability to put on a happy face when faced with a gift of an unattractive baby rattle was shown to predict their knowledge of the often-unspoken rules of acceptable behavior in society. The results speak to a child's potential to develop "socially appropriate expressive behavior" and a visibly even temperament, according to the authors.Speaking of which, here's a counter-experiment proposal. My brother and I discovered long ago that if you look absolutely confident when giving a present you know full well to be unattractive, you're more likely to get a positive response when it's unwrapped. But if you show uncertainty, the resulting tension is likely to be unbearable. We've pulled off some seriously tacky gifts to family members with this tactic.