Last post, I was discussing paternal investment in children. The point of that post was to draw attention to the fact there are often rather good biological reasons for why we might expect men and women to be differentially interested in investing their time and energy in raising children versus doing other adaptive things. This is not to say that we shouldn’t expect men to be interested in investing in children, of course; just that we shouldn’t expect such things to be indiscriminate or motivated by the same factors as women’s altruism. I wanted to expand on one of those ideas a bit more today: specifically, the idea that men lack assurance in their paternity when fertilization takes places inside the female, whereas women can be 100% certain the child they give birth to is theirs. “Certain”, in the former context, refers to the notion that women were unlikely in need of a solution the adaptive problem of maternity certainty, as giving birth to a child was an honest and reliable signal that the child was related to the mother genetically.

“Little does she know it’s not her child” – No one, ever

The first study I wanted to draw attention to concerns the resemblance of a child to their parents. Naturally, as children inherit half of their genes from each parent, we should expect that children tend to resemble their parents with respect to a number of external and internal features. That much is pretty noncontroversial. However, since fathers cannot be assured of their paternity, we might expect men to attend to certain similarities between them and their would-be children when calculating the likelihood that a given child is actually theirs. If an Asian woman gives birth to a Black child, her Asian husband can likely be fairly assured that the child in question is not, in fact, his, and there might have been some infidelity involved somewhere along the line. One might – and, indeed, some have – make the corresponding argument that we might expect children to physically resemble their father more than their mother. The logic would go roughly as follows: if the child resembles their father more, they might receive more parental investment from the father, as he can be more certain the child is his. So, since that tends to be a good thing for the survival and reproductive prospects of the child, we might expect children to bias their resemblance towards their fathers (foregoing for the moment the precise mechanisms through which that might be achieved).

There’s a major issue that such expectations run into, however: reality. In a 1999 paper, Berdart & French collected photos of parents and their children from 28 families. The children’s photographs were taken when they were approximately 1, 3, and 5 years old; the parent’s pictures were all from when the child was about 1 year old. During each trial, the participants (180 undergraduates) were presented with a single picture of a child alongside three women or three men and asked to try and identify the child’s parent. This process was repeated 28 times for each subject. If children tend to resemble their fathers more than their mothers, we should also expect people to be better at matching the child to their father than their mother. This effect failed to materialize, however: for one-year old children, the average correct matching to the father (13/28) was not different than correct matching to the mother (12/28); similar findings obtained for the three-year olds (13/28 and 13/28, respectively) and five-year olds (14/28 and 14/28, respectively).

So while child did certainly tend to resemble their parents consistently (though clearly less than perfectly), they failed to resemble their fathers more than their mothers. Berdart & French (1999) suggested that there might be a rationale for this lack of distinct resemblance: if fathers were good at figuring out which children were theirs, they would presumably also be good at figuring out which children were not theirs, and withhold investment from the latter group. I don’t want to spend too much time on this point other than to note that it’s not a particularly strong one, as it would be good for the ostensible fathers if they had such a skill, and the ill effects on the unrelated child shouldn’t be expected to have an impact on its adaptive nature. Nevertheless, the important point here is that children do not appear to actually resemble their father anymore than their mother. Reality need not always get in the way of perceptions, though.

Fitness is 99% instagram filters

In general, having perceptions that match up to reality is a good thing. If you think you can succeed where you will fail, you’re more likely to waste your time; it you think you will fail when you can succeed, you’ll miss opportunities. Things like that. The exception to that rule concerns contexts of persuasion. There are beliefs I might prefer you to have because they would make me better off, rather than because they are true. So, if some part of my brain that deals with persuading others holds an incorrect belief, that’s not necessarily a problem. As the last post touched on, if people can convince others certain sex differences are due to sexism, that might have some useful implications for certain groups of people to the extent that people are trying to avoid being perceived as sexist and are willing to take steps to remediate the situation. For the present purposes, however, if women are trying to extract investment from men for their children, it would be in those women’s best interest if the man in question believes the child in question is actually related to him, as men are more likely to invest in child on that basis alone. Accordingly, we might predict that women will be more likely to try and convince men that their children resemble them.

Enter some research by Daly & Wilson (1982) that examined the spontaneous utterances of people following the birth of a child. Their first sample consisted of 111 births which had been taped; the fathers were present in 42 of them. From those 111 tapes, approximately 70 comments about the baby’s appearance were recorded. When it was the mother speaking, she remarked on the baby’s resemblance to the father in 16 instances, and the baby’s resemblance to herself 4 times. By contrast, when the father was speaking, he remarked on how the baby resembled the mother 4 times, and himself only once. Further, every time the resemblance to the mother was commented on, the utterance was singular; when the father’s resemblance was being discussed by the mother, however, six of them contained repetitions (e.g. “He looks like you…He’s got your eyes”). Immediately following the birth of a child, then, the resemblance to the father appeared to focused on specifically by the mother. While the mother was nominally more likely to comment on the resemblance to the father in his presence (75%) relative to his absence (47%), this difference didn’t reach significant with the small sample size.

A follow-up study surveyed the responses of mothers, fathers, and the relatives of both concerning the child’s resemblance. Responses came back from about 230 parents and 150 relatives. In all cases, each group suggested the child looks more like the father than the mother by a ratio of at least 2:1. This is in slight opposition to the previous results insomuch as both mothers and fathers said the child looked more like the father. This may have something to do with sampling bias, though, as only about 1/5 of the sample returned any surveys. It seems plausible, as the authors note, that “...fathers rankled by any serious suspicion of nonpaternity would be unlikely to find the questionnaire an amusing diversion“. It possible, then, that fathers might be overstating their physical resemblance to the child in surveys as signals of their unwillingness to abandon investment in the child or relationship, but that’s just speculation on my part. The videos, by contrast, might have proven to be more of an unbiased sample, freer from demand characteristics. Though it’s difficult to say, it’s worth noting that around 25% of the survey respondents reported that “everyone” in their life said the baby looked like the father, as compared with no one reporting comparable utterances about the mother. This is in spite of the finding that children don’t particularly resemble the father over the mother in a matching task, suggesting that such comments might represent social politeness, rather than accurate perceptions.

“She looks just like both of you…”

To repeat the major point here, there can be benefits to perceiving the world in inaccurate ways when you are trying to convince other people of things. Whether that thing is the resemblance of the child to a parent or whether sex differences are due sexism is quite irrelevant. It is likely, in many of these cases, that the part of the brain doing the talking legitimately believes those perceptions so as to better convince others, while different parts of the brain might disagree. Now, in this case, we happen to have data to suggest that the perceptions – or at least what people say about their perceptions – are incorrect; we also have a relatively straightforward theory for explaining why we might expect this might be the case. In many other cases we are not so fortunate.

References: Berdart, S. & French, R. (1999). Do babies resemble their fathers more than their mothers? A failure to replicate Chistenfeld & Hill (1995). Evolution & Human Behavior, 20, 129-135.

Daly, M. & Wilson, M. (1982). Whom are newborn babies said to resemble? Ethology & Sociobiology, 3, 69-78.