Birth order does not affect ability to detect kin

Fasolt, V., Holzleitner, I. J. , Lee, A. J. , O'Shea, K. J. and Debruine, L. M. (2019) Birth order does not affect ability to detect kin. Collabra: Psychology, 5(1), 35. (doi: 10.1525/collabra.235)

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Previous studies suggest that birth order affects kinship detection ability. Kaminski et al. (2010) argued that firstborns use contextual cues (e.g., maternal perinatal association) to assess kinship in their own family, leading to a disadvantage in assessing kinship from facial cues alone in strangers. In contrast, laterborns do not have the contextual cue of maternal perinatal association and hence rely more on facial cues, leading to an advantage in detecting kin from facial cues alone. However, Alvergne et al. (2010) found no evidence in support of such a birthorder effect. The current study aimed to replicate previous studies with better suited methods to determine the effect of birth order on kin recognition. 109 raters viewed 132 pairs of photographs of children (aged 3–17 years), and indicated whether each pair was related or unrelated. Half of the pairs were sibling pairs and half were unrelated child pairs that were age- and gender- matched to the related pairs. No image was shown more than once, related pairs were not known to be related to any other image in the study, and individuals from unrelated pairs were not known to be related to any other image. We used binomial logistic mixed effects modelling to predict kinship judgments from relatedness and birth order (with image pair and rater as random factors). Relatedness was the main factor driving kinship judgments; related child-pairs were more than twice as likely as unrelated pairs to be judged as kin. Kinship judgment accuracy was unaffected by rater birth order. These findings indicate that laterborns did not have an advantage in detecting child sibling pairs. Pre-registration, data, code, and preprint available at

Item Type:Articles
Glasgow Author(s) Enlighten ID:DeBruine, Professor Lisa and Fasolt, Vanessa and Lee, Dr Anthony and O'Shea, Dr Kieran and Holzleitner, Dr Iris
Authors: Fasolt, V., Holzleitner, I. J., Lee, A. J., O'Shea, K. J., and Debruine, L. M.
College/School:College of Medical Veterinary and Life Sciences
College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Collabra: Psychology
Publisher:University of California Press
ISSN (Online):2474-7394
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Collabra: Psychology 5(1):35
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
672531KINSHIP: How do humans recognise kin?Lisa DebruineEuropean Research Council (ERC)647910RI NEUROSCIENCE & PSYCHOLOGY