What can the Thatcher illusion tell us about face processing in the brain? Commentary on Psalta, Young, Thompson, and Andrews (2014)

Referring to fSTS, the authors conclude: “Our results demonstrate clear evidence for orientation-dependent sensitivity to changes in facial expression in a key component of the neural network underlying face perception.” [...]Bartlett and Searcy (1993) showed that the grotesqueness of the Thatcher illusion is caused not by the expression of the face but rather by the disruption of the normal face configuration, which led them to argue: “The Thatcher illusion cannot be explained as an effect of inversion on the encoding of expression.” [...]it is not clear whether the grotesque appearance of the Thatcher illusion is best described as an expression of the face or as a feeling of the viewer invoked by the bizarreness of the image. First is the lack of correction for multiple comparisons despite the authors' tests for an interaction in three face-selective regions: “Our reasoning was that any region that contributes to the perception of the Thatcher illusion should show a greater response … [...]this difference in response should be evident for upright but not inverted faces.” [...]these shortcomings related to null hypothesis testing could have been compensated by presentation of effect sizes and more informative figures (Wilcox, 2006; Allen et al., 2012).