Further pinpointing Mona Lisa’s elusiveness

…although peripherally perceived facial expressions affect the appreciation of faces, Mona Lisa’s smile seems to constitute only part of her enigma. She keeps her mystery, even when one catches her smile.

Concludes the latest research into the elusiveness of the Mona Lisa smile, which has recently been published in the online version of the journal Psychological Science.
Researchers at the Department of Experimental and Neurocognitive Psychology, Freie Universität Berlin, the Department of Psychology, University of Bamberg and the Department of Psychology and Center for Neurocognitive Research, Paris-Lodron-Universität Salzburg, showed photos of one hundred morphed female faces (each in a smiling and a neutral version) to 16 test subjects who were monitored via an eye-tracker system.
The subjects also answered questions regarding the attractiveness, trustworthiness and mysteriousness of the images. Subsequent analysis of the results confirmed an earlier proposal by Margaret S. Livingstone ( Science, 17 November 2000: Vol. 290. no. 5495, p. 1299, letters ) that :

‘‘…you can’t catch her smile by looking at her mouth. She smiles until you look at her mouth’’

see : Mona Lisa’s Smile–Perception or Deception?
Isabel Bohrn, Claus-Christian Carbon and Florian Hutzler
Psychological Science, published online 16 February 2010