title: Social communication and emotion difficulties and second to fourth digit ratio in a large community-based sample.
abstract: BACKGROUND
  Recent research investigating the extreme male brain theory of autism spectrum disorders (ASD) has drawn attention to the possibility that autistic type social difficulties may be associated with high prenatal testosterone exposure. This study aims to investigate the association between social communication and emotion recognition difficulties and second to fourth digit ratio (2D:4D) and circulating maternal testosterone during pregnancy in a large community-based cohort: the Avon Longitudinal Study of Parents and Children (ALSPAC). A secondary aim is to investigate possible gender differences in the associations.
  
  
  METHODS
  Data on social communication (Social and Communication Disorders Checklist, N = 7165), emotion recognition (emotional triangles, N = 5844 and diagnostics analysis of non-verbal accuracy, N = 7488) and 2D:4D (second to fourth digit ratio, N = 7159) were collected in childhood and early adolescence from questionnaires and face-to-face assessments. Complete data was available on 3515 children. Maternal circulating testosterone during pregnancy was available in a subsample of 89 children.
  
  
  RESULTS
  Males had lower 2D:4D ratios than females [t (3513) = -9.775, p < 0.001]. An association was found between measures of social communication and emotion recognition, and the lowest 10 % of 2D:4D ratios. A significant association was found between maternal circulating testosterone and left hand 2D:4D [OR = 1.65, 95 % CI 1.1-2.4, p < 0.01].
  
  
  CONCLUSIONS
  Previous findings on the association between 2D:4D and social communication difficulties were not confirmed. A novel association between an extreme measure of 2D:4D in males suggests threshold effects and warrants replication.
authors.affiliation: Institute of Child Health, 30 Guilford Street, London, WC1N 1EH UK.
authors.forename: Manuela
authors.initials: M
authors.lastname: Barona
authors.affiliation: Institute of Child Health, 30 Guilford Street, London, WC1N 1EH UK.
authors.forename: Radha
authors.initials: R
authors.lastname: Kothari
authors.affiliation: Institute of Child Health, 30 Guilford Street, London, WC1N 1EH UK.
authors.forename: David
authors.initials: D
authors.lastname: Skuse
authors.affiliation: Institute of Child Health, 30 Guilford Street, London, WC1N 1EH UK ; Department of Psychiatry, Icahn Medical School at Mount Sinai; Mindich ChildHealth and Development Institute, Icahn Medical School at Mount Sinai, 31428 Madison Ave, New York, NY 10029 United States.
authors.forename: Nadia
authors.initials: N
authors.lastname: Micali
keywords: ALSPAC; Autism; Emotion recognition difficulties; Second to fourth digit ratio; Social communication; Testosterone