1. What taste reactions are babies born with?
Newborns can tell the basic tastes apart, and they show it on their faces. A review of research on infant facial expressions explains that babies react in a recognizable way to four of the five basic tastes. Sweet and savory ("umami") tastes tend to be welcomed, while bitter and sour tastes tend to be refused [1].
These faces are a reaction, not a memory. A newborn is not saying "I remember liking this." The reaction is better pictured as a starting point, something like the first rough sketch of a drawing. Which particular foods end up on your "yes" list is not drawn in yet. That part gets filled in by experience, which is the rest of this article.
2. Can a baby learn a flavor before eating any food?
A team at the Monell Chemical Senses Center in Philadelphia tested this with carrot juice. Flavors from what a mother eats reach the fluid around a baby before birth, and later reach the baby in breast milk. The researchers asked pregnant women who planned to breastfeed to drink either carrot juice or water during pregnancy, during breastfeeding, or in both periods [2].
Later, when the babies began eating cereal, they were videotaped eating plain cereal and carrot-flavored cereal. Babies whose mothers had drunk carrot juice made fewer unhappy faces at the carrot cereal than at the plain one, while babies in the water group showed no such difference. Their mothers also rated them as enjoying the carrot cereal more [2].
The study has limits. The amount eaten and the length of the meal showed only trends that were not statistically reliable [2]. The study looked at babies, not at what they would like as adults. What it suggests is that "familiar" can begin before a first bite. The authors noted that this may help explain why different cultures grow up with different favorite flavors [2].
3. Does a child learn to like a food by tasting it?
Yes, and looking is not enough. A review of how infants respond to tastes reports that facial reactions and the amount eaten can both change with experience, and that measuring the two together helps show how early experience builds food liking [1]. Put simply: the foods a child actually gets to taste are the ones the child can learn to like.
4. Why does a food you got sick on suddenly taste awful?
Likes are not the only thing learned. If you feel sick after eating something, you may avoid that food for a long time, even if the food had nothing to do with your illness. Scientists call this "conditioned taste aversion."
The classic study, from 1955 by John Garcia and colleagues, used rats. Rats that drank sweetened water while being exposed to radiation, which made them ill, later avoided that sweet water [3]. The surprising part is how fast and how patient this learning is. One pairing can be enough, and the illness can arrive hours after the taste [3]. One way to picture it: the body files away "that taste was suspicious" as a safety rule.
A caution about my sources. I could confirm this from a reference summary of the 1955 work, not from the original paper. And rats are not people: I did not find a source here showing how often the same kind of learning happens in people, so I cannot give a number.
5. How many tries does it take before a disliked vegetable gets easier?
The most useful news is that dislikes can change. A study at the University of Leeds in the UK offered 332 children aged 4 to 38 months a new vegetable, artichoke puree, five to ten times. The researchers noted that parents often stop after about five tries, and the guideline they cite is at least eight to ten [4].
The children responded in different ways. About 40% were "learners" who ate more over time, 21% ate nearly all the puree at almost every session, 16% ate almost nothing even after five tries, and the rest ate more on some tries and less on others. Younger children ate more than older ones, and older children in the group were more likely to be non-eaters [4]. So "eight to ten tries" is a guideline and not a promise.
Researchers also see a hard stretch in the preschool years, when children become wary of new foods ("food neophobia"). Doctoral work from Leeds found this wariness seems to limit how well repeated tasting works, though intake still rose significantly [5]. A review of programs for preschoolers concluded that giving children repeated tastes worked best of the methods compared for raising vegetable eating, while noting a gap in evidence for very fussy eaters [6].
6. How could you test one of your own dislikes?
Likes and dislikes are built from a starting point, flavors met early, repeated tastes, and sometimes one bad experience. That is why a "no" can turn into a "maybe."
If you want to try it, do it with an adult at home. With an adult's help, pick a food they say is safe for you to eat. If you want to, try a tiny, safely prepared bite on different days, and write down how it tasted each time. You never have to finish it, and you can stop whenever you want. Do not try any food you are allergic to. A notebook like this is a record of one person, not a scientific experiment, but it can show whether your own "no" moves.
To read more, start with the abstracts in the source list below. They are written for scientists but are short.