Smiles and Leniency

Research conducted by: Marianne LaFrance and Marvin Hecht

Case study prepared by: David Lane

Dale Carnegie stated that smiling helps win friends and influence people. Research on the effects of smiling has backed this up and shown that a smiling person is judged to be more pleasant, attractive, sincere, sociable, and competent than a non-smiling person.

There is evidence that smiling can attenuate judgments of possible wrongdoing. This phenomenon termed the "smile-leniency effect" was the focus of a study by Marianne LaFrance & Marvin Hecht in 1995.

Questions to Answer
Does smiling increase leniency? Are different types of smiles differentially effective?

Design Issues
There was a single person used for all the conditions. This may limit the generalizeability of the results.

Descriptions of Variables
Variable Description
Smile 1 is false smile
2 is felt smile
3 is miserable smile
4 is neutral control
Leniency A measure of how lenient the judgments were.


LaFrance, M., & Hecht, M. A. (1995) Why smiles generate leniency. Personality and Social Psychology Bulletin, 21, 207-214.

  1. Create parallel boxplots for the four conditions.
  2. Find the mean, median, standard deviation, and interquartile range for each group.
  3. Create back-back stem and leaf displays for the false smile and neutral conditions (It may be hard to find a computer program to do this for you, so be prepared to do it by hand).
  4. Compute a one-way ANOVA.
  5. Use the Tukey test to compare each mean to each other mean.
  6. Compare each mean to the neutral mean using Dunnett's test.