Holzleitner IJ, Querci T, Fasolt V, O'Shea KJ & DeBruine LM (2019). Developing methods for more ecologically valid face stimuli in kinship research. Human Behaviour and Evolution Society in Boston, USA. May 2019.

Previous studies on the effects of kinship cues in prosocial/sexual contexts have often used images manipulated to resemble the observer by globally transforming face shape. Here, we test in an adult sample of full biological siblings whether sibling resemblance is a global trait and/or driven by specific facial dimensions,and whether face-morphological measures predict accuracy of third-party kinship judgments in a matching task.From a database of 3D face images of relatives and non-relatives, we algorithmically chose the maximum number of sibling pairs where both siblings were aged 18+ and an age-and sex-matched foil image was available.3D face models were subjected to a principal component analysis of shape, and two similarity measures derived: global distance in 3D face space, and distance on individual face dimensions (shape PCs). Preliminary analyses suggest that sibling faces are closer in 3D face space than foil pairs, although global distance did not predict accuracy of kinship judgments.Similarity on one of the extracted shape PCs was found to both predict relatedness as well as accuracy of kinship judgments. Our results are a first step towards creating stimuli specifically manipulated in dimensions linked to actual relatedness as well as reliably eliciting kin recognition.

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