Face Perception: How many Dimensions are there?

How many dimensions are there in face perception? Traditionally, both cognitive and social psychology have considered 3 dimensions: warmth, competence, and dominance. Other dimensions have received so far few if any consideration but appeared important in other areas of social judgment: trustworthiness, morality, openness, and neuroticism. We presented randomly a total of 80 faces to 323 participants. They were asked to rate a subset of faces on 21 items (three per dimension) on a 7-point Likert scale. A total of 323 participants * 10 faces * 7 dimensions * 3 items = 68880 ratings was collected. The results of an exploratory factor analysis based on parallel selection suggested a 7 factors structure explaining 61% of the variance. Bartlett’s Test of Sphericity gave a p-value < 0.001. The normed χ2 of this model was 4.83. An EFA enforcing a 7-factor structure (minimum residual extraction and promax rotation) revealed that all items loaded on their expected dimension. Only the traditional 3 dimensions and trustworthiness had a sum-of-square loadings > 2, altogether explaining 40% of the variance. In order to test this 7-factor structure, we performed a CFA. The normed χ2 was 16.90. Parsimony of the model was reasonable (RMSEA = .07 with 90%CI [.068:.072]), reasonably different from a null model (CFI = .92), and the overall difference between the observed and predicted correlations was also satisfactory (SRMR = .07). Are the 3 traditional dimensions enough or should there be more? If so, how many? This question should be addressed in future studies.