It all comes down to bitterness.
Over time humans have evolved to find things that are dangerous to eat taste bitter. Therefore, we don’t eat them, and therefore we live to eat another day.
'If you go outside and pick up a leaf, put it in your mouth and chew it, it's invariably going to be bitter. That's because we've got a system which says it may be dangerous,' explains Russell Keast, director of the Centre for Advanced Sensory Science at Deakin University.
We’re programmed to be suspicious of foods that taste bitter.
These bitter flavour compounds are more common in vegetables like Brussels sprouts, broccoli, and foods like olives.
Children are also more sensitive to bitter flavours - which their bodies are telling them could indicate that the food is dangerous.
With these facts combined it makes perfect sense why little ones wince at the idea of having to finish their veggies.
So how come adults get over it? (Mostly)
Humans are, by nature, highly adaptive. Continual exposure to bitter foods, therefore, can help us build up a taste for them. Just as well - because veggies are very good for you.
How many vegetables would you say you ‘used to hate’ as a kid but now enjoy?
The same is true for other things like beer, wine, and coffee which we may have hated the first time we tasted.
In this case Keast suggests it’s the pleasure we take from sipping a beer at a barbie, or the energy we get from the flat white on a busy morning, that helps us grow to tolerate - and even like - the bitter flavours in these grown-up drinks.