Bayesian recognition in baby similarity

When people come to see small babies, it’s almost like they’re obliged to offer their opinions on who the child looks like. Most of the time it’s an immediate ancestor – either a parent or grandparent. Sometimes it could be a cousin or aunt or uncle as well. Thankfully it’s uncommon to compare babies’ looks to those who they don’t share genes with.

So as people have come up and offered their opinions on who our daughter looks like (I’m top seed, I must mention), I’ve been trying to analyse how they come up with their predictions. And as I observe the connections between people making the observations, and who they mention, I realise that this too follows some kind of Bayesian Recognition.

Basically different people who come to see the baby have different amounts of information on how each of the baby’s ancestors looked like. A recent friend of mine, for example, will only know how my wife and I look. An older friend might have some idea of how my parents looked. A relative might have a better judgment of how one of my parents looked than how I looked.

So based on their experiences in recognising different people in and around the baby’s immediate ancestry, they effectively start with a prior distribution of who the baby looks like. And then when they see the baby, they update their priors, and then mention the person with the highest posterior probability of matching the baby’s face and features.

Given that posterior probability is a function of prior probability, there is no surprise that different people will disagree on who the baby looks like. After all, each of their private knowledge of the baby’s ancestry’s idiosyncratic faces, and thus their priors, will be different!

Unrelated, but staying on Bayesian reasoning, I recently read this fairly stud piece in Aeon on why stereotyping is not necessarily a bad thing. The article argues that in the absence of further information, stereotypes help us form a good first prior, and that stereotypes only become a problem if we fail to update our priors with any additional information we get.

3 thoughts on “Bayesian recognition in baby similarity”

  1. I agree with you and I am sure your observation on the logic behind this may help people working on AI to put some intelligence to a machine, which I am sure they are doing it

  2. I dislike the practice of identifying babies as bearing closer resemblance to one parent, or grandparent.
    However, having been put on the spot by the parent(s) of babies multiple times, I just look at the baby closely (appearing to make deep analysis), and then randomly pick one of the two parents. In one instance, when the inquirer was a grandmom (dad’s mom), I said the baby resembled the grand dad, just to please her ego.
    If you could test out this behaviour in a wider sample, maybe everyone is just randomly assigning resemblances (adjusted for situation, people present, and the inquirer).

  3. The look of the baby’s face changes dramatically as it goes from newborn to infant to toddler. Most of the folks who visit a newborn know this (they are grandparents or parents) and yet they engage in this redundant face matching! I think they do this mostly to give some boost to the baby’s parent/family they are closer to ?

Leave a Reply to Ashwin Cancel reply