Given a choice between raw broccoli and a salty cracker, 18-month-old children will invariably choose the tastiest: the biscuit.
But if they watch an adult saying ''yuk'' when eating crackers and ''yummy'' while munching on broccoli, the children realise the grown-up has a different outlook to them.
When asked to give the adult some food, 18-month-olds will offer what the person seems to like: some broccoli.
One-year-olds, on the other hand, would still give their own preference: a cracker.
The finding is one of the insights into the minds of children made by an American psychologist and philosopher, Alison Gopnik, that are changing understanding of how babies see the world around them.
''The 18-month-olds have gone beyond empathy to genuine altruism … to help the adult get what they want,'' said Professor Gopnik, from the University of California, Berkeley, who presented a Sydney Ideas talk at Sydney University last night.
Previously, she said, it had been thought this ability, which underpins morality and social success, did not develop until about seven years of age.
Toddlers can also analyse statistics and carry out experiments. ''Our research shows that even the youngest babies have learning abilities that are more powerful than those of the smartest scientists and most advanced computers.''
Professor Gopnik, author of The Philosophical Baby: What Children's Minds Tell Us About Truth, Love and the Meaning of Life, was initially intrigued by why humans have a much longer period of helplessness as babies than other animals.
Her explanation is that it gives them time to learn about the world and other people, while their brains are still plastic and many new neural connections can form.
Adults are the workers, but babies are the ''research and development division of the human species''.
They are more conscious of events around them than adults, she said, relating the observations of a store detective from a high balcony.
Shoppers rarely noticed him, he told her, but little children would quickly see and wave.
Even eight-month-old babies can unconsciously understand probabilities, she said. They stare longer at unexpected results, such as a lot of red balls being drawn out of a box they know contains mainly white balls.
Her advice for parents is not to waste money on educational videos or flash cards, but to let babies learn the natural way, by exploring and pretending.
Adults can also learn from infants by ''seeing the world with children's eyes'', said the mother of three, who added that a routine walk to the corner can be a rich experience from an infant's viewpoint.
Her research on the amazing baby brain is also aimed, in part, at identifying ways for scientists and computers to improve their performance.