I absolutely believe picky eating is a learned behavior. The wide varying cultural differences in food already tells us there's nothing biologically innate about the preferences.

Toddlers will observe their parents facial expressions and behaviors even as they're being served. If you scrunch your nose when giving them broccoli, they won't like it. If you incentivize eating it, they learn they're not "supposed" to like it. At the other extreme, if the parents fight for the last piece of broccoli the kid will happily join in, in my direct experience. Somehow we have convinced our toddler that broccoli is the best thing ever and lollipops will break her teeth and should be avoided :D Your reaction to hearing about this kind of "conditioning" is also no doubt a product of your own environment.

For things like sour or spicy which may be unpleasant at first, repeated and consistent small exposure over time changes their preferences almost without fail. Millions of Korean kids loves Kimchi as a staple, if you could replicate that environment your kid would too.

  > Toddlers will observe their parents facial expressions
  > and behaviors even as they're being served.

I did an experiment with this. When my daughters were around 4 and 6 I introduced them to Shproti, a small canned fish, as a desert. I would only let them eat it on special occasions, and only if they were well behaved. For probably five years they would reject ice cream in favour of these canned fish if given the chance.

I do not know who broke to them the secret, but now the little one does not like them anymore. The older still eats the fish with me, but of course no longer as a desert.

This hasn't been my experience with our twin toddlers and 5 year old. What they like is all over the place. We don't force or bribe them to eat anything - we put their options on their plate (usually around 4 things) and let them eat whatever they want. Everything they eat my wife and I eat, and we don't make things we don't like to eat.

Usually only around half of what we serve them will be eaten by all 3 kids. What they don't eat I generally eat for lunch the next day.

There are also some completely random habits. Take asparagus for example. One toddler won't eat the tips.

Right. As weird as it sounds I think you have to "practice" liking certain foods.

I used to hate ginger but drinking ginger kombucha, which has a ginger taste but isn't overwhelming, slowly acclimated me to the taste of ginger. A few months later and I actually liked ginger.

I can still see why I use to hate it but it's just...more palatable now.

The more I looked into flavors (bitter, salty, sour, sweet, umami) I realized I almost always had issues with sour. Not anymore.

> Right. As weird as it sounds I think you have to "practice" liking certain foods.

We do. The taste buds of young children are attuned to liking sweet. Milk is sweet (lactose), and poisonous foods are usually not, so its of evolutionary use. As is switching teeth.

From what I read, it takes about 10 times till a child likes something they disliked before. Force feeding leads to trauma though; so we provide our child with options and encourage her to sample. One particular quote I use (translated from Dutch): "you don't know yet how it tastes. If you try it you'll find it out. Maybe you're missing out?" I want to stimulate her curiosity because its a trait I like (in both her parents). She won't get an alternative food though, and she will be allowed her desert regardless.

As for sour, we combine yogurt (sour) with custard (vanilla, sweet) at times. The balance is more in favor of the latter for the child; parents eat a more sour version. From my memory I disliked bitter as child (some vegetables are abundant with that taste). Now I drink coffee black daily, and love bitter vegetables, as long as the taste is combined with herbs, spices, pepper, and other flavors such as sweet/sour/salty/umami (while respecting the bitterness as being the dominant taste).

Well, acquired taste is absolutely a thing, as probably anybody who likes coffee, beer, red wine, or a thousand other things can readily attest to. We're hardwired to like energy-rich food, most other things are learned.

I'm a bit surprised this came as a revelation to you. People in my social context all knew that tastes are acquired. And liking certain things was seen as a sign of maturity, leading people to brag about liking stuff before they actually did.

Also, one's tastes can change over time. In my case I had never considered that possibility until it happened to me. As a kid, I would not touch salad with a 10 foot pole. But at one point in early adulthood I tried one and actually enjoyed it. A bit later I realized that what I really like are a lot of savory, acidic flavors (salsa, mustard, tomato sauce, vinegar), which of course includes many salad dressings.