Prenatal sex hormones, digit ratio, and face shape in adult males.

OBJECTIVES: Several reports have demonstrated a relationship between second to fourth digit ratio (2D:4D) and facial shape, suggesting that prenatal sex hormones play a role in the development of the craniofacial complex. Using 3D surface imaging and geometric morphometrics, we test the hypothesis that decreased digit ratio (indicative of increased prenatal androgen exposure) is associated with a more masculine facial phenotype. METHODS: 3D facial surface images and digit measures were collected on a sample of 151 adult males. Facial landmarks collected from the images were aligned by Procrustes superimposition and the resulting shape coordinates regressed on 2D:4D. Variations in facial shape related to 2D:4D were visualized with deformable surface warps. RESULTS: A significant statistical relationship was observed between facial shape variation and 2D:4D (p = 0.0084). Lower 2D:4D ratio in adult males was associated with increased facial width relative to height, increased mandibular prognathism, greater nasal projection, and increased upper and lower lip projection. CONCLUSIONS: A statistical relationship between 2D:4D and facial shape in adult males was observed. Faces tended to look more masculine as 2D:4D decreased, suggesting a biologically plausible link between prenatal androgen exposure and the development of male facial characteristics.

Dissociation of two kinds of source attributions.

We examined the relationship between two different source attribution errors. One error found primarily in the cognitive psychology literature is the belief that one is an author of an idea when one is not. The other error, reported in the social psychology literature, occurs when people overestimate how long they have known an idea. Although somewhat different, both errors are a form of misappropriation of ideas to oneself. We investigated both attributions and found that when participants performed a more elaborate encoding task, erroneous claims of authorship were reduced but length-of-knowing judgments increased. The results are discussed in terms of the cognitive processing that is likely to give rise to each source attribution.