On Superstimuli

A superstimulus is, quoth Wikipedia:

A supernormal stimulus or superstimulus is an exaggerated version of a stimulus to which there is an existing response tendency, or any stimulus that elicits a response more strongly than the stimulus for which it evolved.

For example, it is possible to create artificial bird eggs which certain birds will prefer over their own eggs,[1] particularly evident in brood parasitism, and humans can be similarly exploited by junk food[2] and pornography.[3] Organisms tend to show a preference for the stimulus properties (e.g. size, colour, etc.) that have evolved in nature, but when offered an artificial exaggerated stimulus, animals will show behaviour in favour of the artificial stimulus over the naturally occurring stimulus.[4]

Many people I talk to think that superstimuli are bad and should be avoided. As I understand it, the thought is something like this: “we evolved to experience a certain stimulus, like sweet fruit. Cake is much sweeter than any sweet fruit in the environment of evolutionary adaptedness. There’s a natural regulatory process in the diet, which cake disrupts. Normally, we want fruit a little bit, and eat enough fruit to have a balanced diet. Because cake is so sweet, we want lots and lots of cake, and that makes our diets more unhealthy. That’s bad, and we should eat diets more like we evolved to eat.”

This claim may or may not be true of cake but it is not true of all superstimuli.

When you look for it, there are superstimuli all over the place. Forget cake: bananas have been subject to thousands of years of selective breeding to be much tastier than anything in the environment of evolutionary adaptedness.

This is what a non-superstimulus banana looks like. Yum.

Or consider sex with birth control. It reduces my inclusive genetic fitness compared to not using birth control. Certainly, I want a good deal more sex when I have birth control than I do when I don’t have access to birth control. And I’m definitely much more turned on by it when I don’t have to worry about babies resulting. Sex with birth control is a far more obvious superstimulus than junk food, but it would be a mistake to conclude that therefore I should become Quiverfull.

We can get more speculative. What about great art? When I watch a Shakespeare play, I’m watching a play by the greatest playwright in English in the past four hundred years—selected out of a group of millions of people. In the environment of evolutionary adaptedness, I would never get to experience a story as great as Hamlet. However, I probably shouldn’t seek out a more evolutionarily normal fiction diet of terrible Wattpad stories about Your Name Here being kidnapped by One Direction.

You can come up with various speculations about why storytelling evolved. Perhaps it’s related to our desire for gossip about other humans, or perhaps it helps us remember important facts, or perhaps it signals that the storyteller has good genes so I should make sure to have sex with him. Since Hamlet is not a real person and (necrophilia aside) I can’t have sex with Mr. Shakespeare, my reading Hamlet probably doesn’t align with the evolutionary purpose of storytelling. (I guess maybe it can teach me some facts about Madness, or Action Versus Inaction, or whatever people think Hamlet is about this year. But it’s far from obvious that I wouldn’t learn equally useful facts watching plays put on by freshmen English majors.)

My life has an enormous amount of art far better than the art I’d have experienced in the environment of evolutionary adaptedness. I listen to more beautiful music (and that’s assuming music isn’t itself a superstimulus). I look at more beautiful pictures (and that’s assuming that e.g. landscape painting isn’t a superstimulus for landscapes that might have had food in the environment of evolutionary adaptedness). Heck, I even enjoy videos of cuter animals (and that’s assuming that cute animals aren’t a superstimulus for babies).

The number of superstimuli humans interact with is exactly what you’d expect. Evolution is trying to maximize our inclusive genetic fitness—that is, the number of grandchildren we have. I don’t care much about my inclusive genetic fitness. I care about the innumerable desires that evolution put in me that, on average, in the environment of evolutionary adaptedness, would have increased the number of grandkids I had. So of course sometimes I’m going to seek out things that are very good at satisfying those desires and reduce my inclusive genetic fitness. I don’t care about that last thing!

Some people worry that interacting with superstimuli would lead to compulsive behavior. Of course, sometimes people behave compulsively. But “is this a superstimulus?” seems to me to not be a very good heuristic. Most people don’t compulsively consume bananas, Shakespeare plays, or rock music. Indeed, having sex without contraception when you don’t want a child—perhaps the single sexual behavior most closely related to why humans desire sex—is often seen as a sign of compulsive sexual behavior.

Indeed, I think the causation goes the other way. People call something a superstimulus if people consume it compulsively or if it’s something we generally disapprove of. Since most people approve of consuming fruit and Shakespeare, it doesn’t get tarred with the same brush—even though it’s hard to argue they’re not. While “superstimulus” might be a useful concept for discussing bird behavior, I really don’t think it’s very useful for most of the human-related purposes to which it has been put.