Wrong About Our Own Desires

by Luke Muehlhauser on March 27, 2011 in Science

It is surprising but true that we can be confused about our own desires. Let me illustrate with a (true) story.

On holiday in Sicily, Anthony Dickinson found a market square in Palermo with watermelons. Later, when he was thirsty, he returned to the square and sated his thirst with sweet watermelon.

A few days later, when thirsty again, he returned to the square. But this time, the sight of the watermelons made him nauseous, and their taste was now disgusting to him.

Anthony didn’t know why his desire for watermelons had changed so quickly until many years later when, studying psychology, he learned that a single pairing of a novel flavor with an upset stomach can create an aversion to the flavor, even if a few hours pass between tasting the novel flavor and the upset stomach.1

Anthony now remembered that, drinking too much red wine that evening, he had been very sick on the same day that he first tasted the watermelons. Because aversion conditioning occurs more in response to novel flavors instead of familiar flavors,2 Anthony had acquired a distaste for watermelon rather than for red wine, which he had drunk many times before.

He had returned to the market square because of his desire for watermelon (to sate his thirst), but upon arriving, he found that he had an aversion to their taste of which he had been totally unaware.

How did this happen?

Anthony is now a leading research in affective neuroscience, and he suggests such confusions occur because of a “dual psychology”:

As a cognitive creature, [Anthony's] search for watermelon was a rational and intentional action controlled by a belief about the route to the square and his desire for watermelons. In contrast, the disgust that he felt… on re-tasting the melon was a manifestation of his nonrepresentational, reflex psychology. Consequently, during the intervening days between his two trips to the market square, these two psychologies appeared to remain radically disconnected and at variance with each other…

…what fused these two psychologies, thereby allowing them to interact in the control of his subsequent behavior, was his phenomenal experience on the second exposure to the melon. It was the experience of nausea and disgust, in conjunction with a perceptual-cognitive representation of the melon as the object of this powerful negative affect, that led to the loss of his desire.3

Since he’s a neuroscientist, Anthony (and his colleague Bernard) went on to test4¬†whether the same confusion could be produced, by the same method, in rats. (Humans share with other mammals much of the brain structure that produces affect, and rats are capable of goal-directed behavior.)

Anthony and Bernard taught the rats to press a lever to get a taste of a novel sugar water solution. Then they made the rats ill with a mild toxin.

If the rats were like Anthony, they should have followed their (cognitive, goal-directed) desire to press the lever when put in its presence at a later time, but upon pressing, they should have found the taste disgusting, and never tasted it again.

And that is exactly what they did. The rats sought out the lever, apparently “thinking” they wanted the sweet sugar water, but upon tasting it, they never tried to taste it again, apparently finding it nauseating do to their conditioned reflex response to the novel sugar water solution.

I don’t know whether Anthony’s theory (“hedonic interface theory”) is correct, but Anthony and his colleagues have amassed a significant amount of evidence in favor of it.

Moreover, I’ve experienced the same thing. Maybe you have, too. Once, I ordered a kind of Subway sandwich I had never ordered before, and later got sick (I don’t remember what from). A week later, I went back to Subway but the smell of the sandwiches made me nauseous, and it was many months before I could enjoy a Subway sandwich again.

Pleasure and desire are complicated things in homo sapiens.

  1. Smith & Roll (1967). Trace conditioning with X-rays as an aversive stimulus. Psychonomic Science, 9: 11-12. []
  2. Ahlers & Best (1971). Novelty vs temporal contiguity in learned taste aversions. Psychonomic Science, 25: 34-36. []
  3. Dickinson & Balleine (2009). Hedonics: the cognitive-motivational interface. In Pleasures of the Brain. Oxford University Press. []
  4. Balleine & Dickinson (1991). Instrumental performance following reinforcer devaluation depends upon incentive learning. The Quarterly Journal of Experimental Psychology, 43B: 279-296. []

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{ 15 comments… read them below or add one }

cl March 27, 2011 at 4:56 pm

Nice photo!

It is surprising but true that we can be confused about our own desires.

I don’t find this surprising at all, but I’m glad you seem to be coming around to it. From here, it’s only a small step towards realizing that a person with good desires would apologize for wantonly violating their own standard of morally responsible speech [cf. Alonzo Fyfe, Faith, Arrogance, and Uncertainty]. Or, if I might put you under the spotlight for a minute… would a person with good desires flagrantly ignore the advice of Dr. Marcel Brass [CPBD 085] by insinuating that Libet falsified free will? Both of these errors directly contradict the stated desires of the agents who made them.

So, are you both wrong about your own desires? If not–which I suspect because I am giving you the benefit of the doubt here–can you please explain these discrepancies?


PDH March 27, 2011 at 5:20 pm

Fascinating stuff. That certainly makes a lot of sense.


mopey March 27, 2011 at 7:03 pm

Any other examples not involving foodstuffs?


mkandefer March 27, 2011 at 7:45 pm

Happened to me with limes after having a few too many vodka tonics with a lime slice. I can now tolerate them somewhwat, but prefer to substitute lemons when it pairs well.


DaVead March 27, 2011 at 8:50 pm

Interesting… I used to love hard-boiled eggs; in egg salad, on their own, whatever. Then one morning I woke up with a bad stomach flu, and threw up after eating some hard-boiled eggs. Since then, probably ten years ago, I’ve never been able to stand the smell or taste of hard-boiled eggs.


cl March 27, 2011 at 8:51 pm

I once ate pizza with pineapple only to later vomit it all out, including through the nasal passages. I cannot for the life of me eat it today. Same thing with chewing tobacco.


Michael March 27, 2011 at 8:55 pm

I find watermelons attractive but unsatisfying. They look big, bright, and colourful. But alas, they only contain a subset of satisfying qualities. They satisfy desires for sweetness and water, but not the desires for chewing, sucking and swallowing a solid, substantial fibrous stream of food. Watermelon disappointingly dissolves in your mouth without satisfying those desires. It also leaves the stomach quickly, rather than give a lasting feeling of fullness. In my experience, I got excited by watermelon as a kid, but repeated tastings conditioned me to believe that it’s simply not worth the effort. Moreover, there’s a distinct pain response to chewing a food so enticing yet disappointing. Watermelon is a pain because it lacks texture. I also find watermelon tastes over-sweet, if there is such a thing. So, between it’s unsatisfying and over-sweet qualities, a nauseating response may be a direct response to the melon itself. Tastes get refined over a lifetime. And red wine may have the same effect of sweetness without texture, making it more likely that your next meal will be a strong desire for solid chewy food.


igor garcia March 27, 2011 at 9:05 pm

Very interesting. It actually happened to me with caramel popcorn during school days. Although I don’t remember if I got sick that day, I ate it only once and then never more. Before that, all I wanted was to taste a caramel popcorn.
About Michael’s comments, I agree the watermelon is a little bit frustrating, but it’s excellent for those who want to lose some weight. It can be used as an afternoon snack for example. Cheers from Brazil!


Rules For March 28, 2011 at 12:32 am

Something similar happened to me with Wilco’s Yankee Hotel Foxtrot. The day I got the album I listened to it on a 90-minute drive during which I felt very nauseous. For a while afterwards (a week or so), I felt nauseous whenever I considered listening to the album.


Robert Oerter March 28, 2011 at 11:59 am

I like the example Sam Harris (I think) gave of going to a foreign country, and being warned to stay away from the US embassy because of the likelihood of terrorist attacks. But when he spoke to the travel agent, and she recommended a hotel with a lovely view of the US embassy, he gladly agreed.

Here it is not just a matter of our rational desires being in conflict with our autonomic nervous system, but of one rational desire (to avoid a dangerous location) being in conflict with another rational desire (to have a nice view). Not only can we be wrong about our own desires, but we can have desires that are completely contradictory, without even being aware of the fact.


David Gerard March 28, 2011 at 2:13 pm

I thought this effect in rats was long well-known. This is why rats are so incredibly hard to poison – such that rat poison is something tasty mixed with an anticoagulant and ground glass.


Rob March 28, 2011 at 3:44 pm

I guess we should hammer another nail in the dualism coffin, but the coffin is so encased with nails there is no room.


Unbeliever March 28, 2011 at 4:33 pm

When I was around 7 or 8 years old, my family went to Luby’s cafeteria regularly, and I discovered lemon meringue pie. I loved it! It was my favorite thing, ever.

Then one day, I got sick. No, it wasn’t after eating lemon meringue — but the MEDICINE I was given was a thick (gelatinous) fluid, yellow, and was trying hard to be “kid friendly” by adding a lemon flavor.

It was THE MOST VILE substance I had ever consumed. To this day, I don’t think I have ever eaten anything more disgusting.

It was YEARS before I could even look closely at a slice of lemon meringue again, much less taste it. Mind you, I knew it would still be the same delicious thing I used to love. But the feeling was visceral; I could not make myself even consider tasting it for many years after that event…

[Now that I've written all that, I'm not sure if my story is related to the phenomena being discussed or not. Oh well...]


cl March 28, 2011 at 11:57 pm


I guess we should hammer another nail in the dualism coffin, but the coffin is so encased with nails there is no room.

For FSM’s sake will you quit preaching materialism already? Especially in the absence of evidence or cogent argument. The fact that some guy felt nauseated by what he previously craved doesn’t prove your pet theory in the least bit. Talk about leaping to conclusions. This is as silly as your remark that “neuroscience falsifies Christianity.” Nah, you’re not preaching dogma at all. Nope. Not at all. You’re totally rational! What are you going to do? Call me a “bitch” because science works, like you did here? Get real!

“I thought I wanted watermelon but then I thought I didn’t, ergo dualism is false!” This is why you should spend some time studying logic instead of preaching scientism.


cl March 29, 2011 at 12:13 pm


Actually, nevermind. Since determinism and free-will are settled issues, I can’t hold you ultimately responsible for such irrationality. I apologize.



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