New research from Germany has found that fathers can identify the body odor of their own children and prefer it over the odor of other prepubescent children. However, their preference for their children’s body odor decreases as the children enter puberty. This decline is especially notable in daughters and becomes more pronounced as daughters progress through puberty. The study was published in Physiology & Behavior.
Body odors play a crucial role in human relationships. They can influence how much a person is trusted, how attractive others find them, and can even convey emotional states. Additionally, body odor provides information about a person’s health, hormonal status, and genetic compatibility, often triggering emotional responses in others. This can lead to bonding through pleasant odors or aversion if the odor is unpleasant.
Body odors are particularly significant in parent-child interactions, as they help develop and maintain a loving relationship. Parents can often recognize their offspring (and possibly other relatives) by smell, and tend to find that smell pleasant. Studies show that familiar or pleasant body odors activate the brain’s reward and pleasure networks, while also reducing stress.
However, the perception of body odor appears to change with a child’s age. One study found that mothers could identify the smell of their children before puberty, but once the children reached puberty, mothers could no longer recognize or prefer their child’s body odor. After puberty, mothers once again perceived their children’s odors as pleasant. There is some indication that this reduction in preference with puberty may apply to sons but not to daughters.
Study author Laura Schaefer and her colleagues set out to investigate whether fathers can also identify their children’s body odor at different stages of development, excluding puberty. They hypothesized that fathers would prefer the body odor of their children, but this preference would decrease as their daughters entered puberty, while remaining unchanged for sons.
In other words, the researchers expected that fathers would continue to like their sons’ body odor throughout all developmental stages, but their preference for their daughters’ smell would diminish once the daughters reached puberty. The researchers suggested that this reduction in preference for opposite-sex children’s odor as they mature could be a biological mechanism to avoid incest.
The study involved 56 fathers and 73 of their biological children, with the children’s ages ranging from newborns to 18 years old. The average age of the fathers was 39. Thirty-nine fathers participated with one child, while 17 participated with two children.
The study was conducted in several phases. In the first phase, participants visited the lab, where the researchers tested the similarity of participants’ immune systems, specifically their Human Leukocyte Antigen (HLA) complexes. These proteins, found on the surface of most cells, play an important role in immune response and also influence the composition of sweat, which affects body odor. Fathers also completed assessments of their olfactory abilities (their ability to identify different smells) and depressive symptoms during this visit.
In the next phase, the researchers collected hormonal samples and body odors from the participants. The children were instructed to use an unscented shower gel (provided by the researchers) and then sleep in an experimental shirt also provided by the researchers. The following morning, the fathers collected the shirts and sent them back to the researchers, who then created body odor samples.
In the final phase, fathers were asked to rate the pleasantness, intensity, sweetness, desirability (how much they wanted to smell it again), and attractiveness of the body odor samples in separate experimental runs. In the final run, they were asked to identify which odor sample belonged to their child.
The results showed that fathers were able to recognize their child’s body odor 33% of the time—significantly better than the 17% success rate expected from random guessing. As hypothesized, fathers performed better than chance in identifying their child’s body odor in all age groups except during puberty. HLA similarity was not associated with recognition ability. Fathers rated the odor of their infant and prepubescent children as more pleasant than that of older children. This effect was especially pronounced with daughters, as fathers’ preference for their daughters’ odor sharply declined as they progressed through puberty.
“Similar to mothers, they [fathers] were able to recognize their own child’s body odor across the developmental span, with exception of early puberty. A loss of familiarity perception due to hormonal transitions altering the body odor may account for that observation. Fathers preferred their own child’s odor over unfamiliar odors in pre-pubertal stages of development, but this effect vanished with the onset of puberty. The reduction in preference related to increasing pubertal status in daughters, but not in sons,” the study authors concluded.
The research highlights the role body odor plays in father-child relationships. However, the study involved a relatively small sample of fathers evaluating only six body odors, all from children. The results might differ if the study were conducted with a larger sample and included a wider range of body odors.
The paper, “Body odours as putative chemosignals in the father-child relationship: New insights on paternal olfactory kin recognition and preference from infancy to adolescence,” was authored by Laura Schaefer, Agnieszka Sorokowska, Kerstin Weidner, Jürgen Sauter, Alexander H. Schmidt, and Ilona Croy.