Abstract
Mothers are able to identify the body odour (BO) of their own child and prefer this smell above other BOs. It has hence been assumed that the infantile BO functions as a chemosignal promoting targeted parental care. We tested this hypothesis and examined whether children's BOs signal genetic similarity and developmental status to mothers. In addition, we assessed whether BOs facilitate inbreeding avoidance (Westermarck effect). In a cross-sectional design, N = 164 mothers participated with their biological children (N = 226 children, aged 0–18 years) and evaluated BO probes of their own and four other, sex-matched children. Those varied in age and in genetic similarity, which was assessed by human leucocyte antigen profiling. The study showed not only that mothers identified and preferred their own child's BO, but also that genetic similarity and developmental status are transcribed in BOs. Accordingly, maternal preference of their own child's odour changes throughout development. Our data partly supported the Westermarck effect: mothers' preference of pubertal boys' BOs was negatively related to testosterone for the own son, but not for unfamiliar children.This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.
Highlights
An affective tight bond between a primary carer and their child provides essential physical and psychological safety, ensuring healthy development of the child [1]
KG, Nümbrecht, Germany) and parents were instructed to explain to the children that they had to chew for 60 s on the salivette until the cotton contained sufficient saliva for laboratory analysis
Using Bayesian statistics [47,48], we explored the likelihood of the first parts of H1 and H2, as for these hypotheses basic assumptions about the effect sizes of preference and identification of one’s own child are available based on a previous publication [11]
Summary
An affective tight bond between a primary carer and their child provides essential physical and psychological safety, ensuring healthy development of the child [1]. In a non-mating context, this ability may contribute to parental olfactory identification and preference of the own child’s BO, especially in ambiguous situations lacking clear indicative cues (e.g. distinguishing between children of the same age with similar hormonal levels). These lines of evidence suggest that BOs may promote bonding and incest avoidance by triggering an evaluation incorporating genetic (HLA, sex), developmental (e.g. age, hormonal status) and environmental factors. We expect an additional effect during puberty, namely that (H5) the assessed pleasantness for the BO of one’s own opposite-sex child (here, sons) decreases as sons transition across puberty, whereas this preference remains stable for the same-sex child (daughters) and for unfamiliar children
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