Now, for the rats, there’s an evolutionarily-adaptive goal of “when in a salt-deprived state, try to eat salt”. The genome is “trying” to install that goal in the rat’s brain. And apparently, it worked! That goal was installed! And remarkably, that goal was installed even before that situation was ever encountered!
I don’t think this is remarkable. Plenty of human activities work this way, where some goal has been encoded through evolution. For example, heterosexual teenage boys often find teenage girls to be attractive and want to get them naked, even before they have ever managed to do it successfully, without a true conscious understanding of their eventual goals. Or babies know to seek out nipple-shaped objects, before they have ever interacted with a nipple.
Well, the brain does a lot of impressive things :-) We shouldn’t be less impressed by any one impressive thing just because there are many other impressive things too.
Anyway I wrote this blog post last year where I went through a list of universal human behaviors and tried to think about how they could work. I’ve learned more since writing that, and I think I got some of the explanations wrong, but it’s still a good starting point.
What about sexual attraction?
Without getting into too much detail, I would say that sexual attraction involves the same “supervised learning” mechanism I talked about here, but with one extra complication: For salt, it’s trivial to get ground truth about whether you are tasting salt—you have salt taste buds sending their signals straight into the brain, it’s crystal clear. But for sexual attraction, you need an extra computational step to get (approximate) ground truth about whether or not you are interacting with a sexually-attractive (to you) person. (Then that approximate ground truth can be the supervisory signal of the supervised learning algorithm.)
So, where does the “ground truth” for “I am interacting with a sexually-attractive (to me) person” come from? First, I think there are hardwired sight cues, sound cues, smell cues, touch cues, etc. See here for details, particularly my claim that these cues are detected by circuitry in the subcortical sensory processing systems (especially the tectum), not in the neocortex. Second, I’m big into empathetic simulation and think they’re central to all social emotions, and I think that it plays a role in all aspects of sexual attraction too, both physical and emotional. That’s a bit of a long story, I think.
I think newborns finding their mother’s nipple are just going by hardwired smell and touch cues, and hardwired movement routines, I presume in the brainstem. Hardwired stimulus-response, nothing complicated! Well, I don’t really know, I’m just guessing.
Now, for the rats, there’s an evolutionarily-adaptive goal of “when in a salt-deprived state, try to eat salt”. The genome is “trying” to install that goal in the rat’s brain. And apparently, it worked! That goal was installed! And remarkably, that goal was installed even before that situation was ever encountered!
I don’t think this is remarkable. Plenty of human activities work this way, where some goal has been encoded through evolution. For example, heterosexual teenage boys often find teenage girls to be attractive and want to get them naked, even before they have ever managed to do it successfully, without a true conscious understanding of their eventual goals. Or babies know to seek out nipple-shaped objects, before they have ever interacted with a nipple.
Well, the brain does a lot of impressive things :-) We shouldn’t be less impressed by any one impressive thing just because there are many other impressive things too.
Anyway I wrote this blog post last year where I went through a list of universal human behaviors and tried to think about how they could work. I’ve learned more since writing that, and I think I got some of the explanations wrong, but it’s still a good starting point.
What about sexual attraction?
Without getting into too much detail, I would say that sexual attraction involves the same “supervised learning” mechanism I talked about here, but with one extra complication: For salt, it’s trivial to get ground truth about whether you are tasting salt—you have salt taste buds sending their signals straight into the brain, it’s crystal clear. But for sexual attraction, you need an extra computational step to get (approximate) ground truth about whether or not you are interacting with a sexually-attractive (to you) person. (Then that approximate ground truth can be the supervisory signal of the supervised learning algorithm.)
So, where does the “ground truth” for “I am interacting with a sexually-attractive (to me) person” come from? First, I think there are hardwired sight cues, sound cues, smell cues, touch cues, etc. See here for details, particularly my claim that these cues are detected by circuitry in the subcortical sensory processing systems (especially the tectum), not in the neocortex. Second, I’m big into empathetic simulation and think they’re central to all social emotions, and I think that it plays a role in all aspects of sexual attraction too, both physical and emotional. That’s a bit of a long story, I think.
I think newborns finding their mother’s nipple are just going by hardwired smell and touch cues, and hardwired movement routines, I presume in the brainstem. Hardwired stimulus-response, nothing complicated! Well, I don’t really know, I’m just guessing.
The interesting thing is that unlike nipple-shaped objects, levers that produce saltwater don’t exist in the ancestral environment.