Babies, smell, and hunger

January 19, 2010 12:13 PM

When your your brain identifies a smell as yummy/edible, is it a learned or instinctual phenomenon?

My husband and I have been debating this since the birth of our daughter three months ago. He maintains that when he's cooking, she instinctively identifies those smells as the smells of food, and is hungry as a result.

I, however, think "yummy" is something learned, and since the kid has only known breastmilk and formula since her first day on the planet, those scents wouldn't trigger her hunger because they're not associated with anything she's ever eaten. They might spark her interest, because hell, everything sparks the interest of a three-month-old, but I don't think she could've possibly made the connection to food.

Who's right?

posted by shiu mai baby to Science & Nature (16 answers total)

I don't think it's possible to correctly answer "nature vs. nurture" questions like this one. We can only provide our best guesses. FWIW, three-month-olds think everything is food, so it's probably more a matter of learning which smells not to associate with yumminess.

As another data point, smells can be very subjective even for grown-ups: I think gasoline smells yummy in almost the same way I think baking cinnamon rolls do. Obviously I know it's not edible (drinkable?) but I can't disassociate the smell and the feeling. I've never had any experience that would cause me to form that connection; I've loved the smell since I can remember. But I know plenty of people hate the smell of gas and think I'm ridiculous for liking it.
posted by The Winsome Parker Lewis at 12:31 PM on January 19, 2010

The usually correct answer to any nature/nurture question is "both." This article seems like a fairly good review of research on whether good/bad smells are innate or acquired.
posted by logicpunk at 12:38 PM on January 19, 2010

Response by poster: That's a great article, logicpunk, thank you. The core of our debate, though, isn't just about odor hedonics, but whether a specific smell can trigger hunger and salivation, even if the person in question has absolutely no association of that smell as belonging to something edible.

TWPL: she's at the fist-nomming stage, but isn't yet reaching and grasping for objects, so the list of things that have been in her mouth is very, very short. :)
posted by shiu mai baby at 12:51 PM on January 19, 2010

Try to explain to yourself how you could "learn" what tastes good. What metric would you use to evaluate the taste of food in order to decide what's good and what's not? Remember, you can't use "tasty" as a criteria!
posted by abc123xyzinfinity at 12:53 PM on January 19, 2010 [2 favorites]

To me it's pretty obvious that it's learned. Otherwise, how would you explain the huge variety of baby foods throughout the world?

Or am I misinterpreting your question?
posted by sid at 1:37 PM on January 19, 2010

Best answer: It's well established now that there is a fairly big genetic component to both taste and smell preference, as in people with one polymorphism think a certain food is wonderful while people with a different one don't, and the human drive to eat is very strong. So I see no reason for the association between tasty smells and tasty food also being partially innate. Environment and genetics interacting together influence all kinds of other aspects of both nutrition and behaviour, why should this be any different? Here's an example found by a really fast search (I'm sure there are plenty more in google scholar, search for things like genetic and taste preference and maybe development): "this review focuses on how genetic predispositions interact with aspects of the eating environment to produce phenotypic food preferences."

but whether a specific smell can trigger hunger and salivation

Put it another way, this would be a pretty basic survival mechanism. Babies need to eat regardless of what their parents do. Given all the other physiological mechanisms in place to keep us eating and prevent us from being too thin (leptin is the most obvious one but there are numerous) I'd be actually quite shocked if this basic mechanism wasn't also inbuilt.
posted by shelleycat at 1:37 PM on January 19, 2010

Possibly of interest: odors from foods ranging from garlic and onions to ginger and strawberries may be nutritional signals that the human nose has learned to recognize (Science Magazine abstract). Lots of possibilities, nothing stated as true in regards to sense of smell.
posted by filthy light thief at 1:38 PM on January 19, 2010

To me it's pretty obvious that it's learned. Otherwise, how would you explain the huge variety of baby foods throughout the world?

Sure the nuances will be learned. It's a great big messy environment/genes/diet interaction, like everything else to do with eating. But I bet the drive to consume broad categories like savoury, sweet, etc are innate as are at least some preferences for certain foods.

(For example, I have the polymorphism that makes coriander taste and smell like soap, so even as a baby I would never have reacted well to it because I'm physically incapable of doing so. There are other polymorphisms that make foods taste better as well.)
posted by shelleycat at 1:41 PM on January 19, 2010

He maintains that when he's cooking, she instinctively identifies those smells as the smells of food, and is hungry as a result.

Tell him that he can work on developing her into a little foodie soon enough, but right now her nose is probably not telling her anything more complex than "good smell/baby not uncomfortable" and "alarmingly bad smell/parents uncomfortable."
posted by desuetude at 1:46 PM on January 19, 2010

Breast milk is hardly a pure substance. It contains oils, proteins, and other things that carry odor. Breast milk from someone who eats wheat and beef will taste different than breast milk from someone who eats rice and fish.

To a certain extent," yummy" is a learned response. However, that learning started taking place much earlier than you would suspect.
posted by 517 at 2:06 PM on January 19, 2010

Both, but let me add that (I think) some research shows that breast-feeding children acquire taste for various foods through their mother's milk.
posted by grobstein at 3:07 PM on January 19, 2010

There are some tastes and smells that you're genetically predisposed to find aversive, but as far as preferences for individual foods is concerned, the relationship between what's innate and what's a result of experience is extremely difficult (if not totally impossible, currently) to decompose.
posted by solipsophistocracy at 3:40 PM on January 19, 2010

Best answer: but as far as preferences for individual foods is concerned, the relationship between what's innate and what's a result of experience is extremely difficult (if not totally impossible, currently) to decompose.

I know of a couple of research groups working on this, one of which is within my organisation, and I think they'd disagree. It is difficult and kind of messy, as are all gene/environment interaction studies, but nowhere near impossible. Here's a review from the second group.
posted by shelleycat at 4:09 PM on January 19, 2010

Whoa, awesome. Thanks a lot!
posted by solipsophistocracy at 6:41 PM on January 19, 2010 [1 favorite]

Response by poster: Well, I'm going to mark this a draw, since there's no clear answer. We're both right!

Thanks so much for all the responses, everyone. There's a lot of really good reading to be had in those articles.
posted by shiu mai baby at 4:29 AM on January 22, 2010

I'm jumping in here a bit late but I'll let you ponder the thought that if you are primarily breastfeeding there is a good chance that your little one may recognize some of the stronger flavors/scents of foods that YOU eat and pass on in your milk (garlic for example).

One of the thoughts about babies and culturally acquired tastes is that they learn to favor flavors that they experience through breast milk.
posted by rosebengal at 11:16 AM on January 24, 2010