About a month ago, after some back-and-forth with several people about their experiences (including on lesswrong), I hypothesized that I don't feel the emotions signalled by oxytocin, and never have. (I do feel some adjacent things, like empathy and a sense of responsibility for others, but I don't get the feeling of loving connection which usually comes alongside those.)
Naturally I set out to test that hypothesis. This note is an in-progress overview of what I've found so far and how I'm thinking about it, written largely to collect my thoughts and to see if anyone catches something I've missed.
Under the hypothesis, this has been a life-long thing for me, so the obvious guess is that it's genetic (the vast majority of other biological state turns over too often to last throughout life). I also don't have a slew of mysterious life-long illnesses, so the obvious guess is that's it's pretty narrowly limited to oxytocin - i.e. most likely a genetic variant in either the oxytocin gene or receptor, maybe the regulatory machinery around those two but that's less likely as we get further away and the machinery becomes entangled with more other things.
So I got my genome sequenced, and went looking at the oxytocin gene and the oxytocin receptor gene.
The receptor was the first one I checked, and sure enough I have a single-nucleotide deletion 42 amino acids in to the open reading frame (ORF) of the 389 amino acid protein. That will induce a frameshift error, completely fucking up the rest of protein. (The oxytocin gene, on the other hand, was totally normal.)
So that sure is damn strong evidence in favor of the hypothesis! But, we have two copies of most genes, including the oxytocin receptor. The frameshift error is only on one copy. Why isn't the other copy enough for almost-normal oxytocin signalling?
The frameshift error is the only thing I have which would obviously completely fuck up the whole protein, but there are also a couple nonsynonymous single nucleotid