A study of 1,000 adults and 1,000 children found that becoming more aware of social norms, acting less on instinct and being preoccupied with phones means kindness diminishes as we age.
While 67 per cent of adults wouldn't consider sharing their food with others, 43 per cent of children would happily hand over some to a friend or loved one.
Youngsters are also more likely to provide you with some extra comfort, with 38 per cent saying they would hug someone for no reason, compared to just 35 per cent of adults.
Despite this, nearly all adults - 96 per cent - would still refer to themselves as ‘kind’.
Bassetts Vitamins, which commissioned the research, put the findings to the test with a behavioural experiment to highlight the differences between adults and children when it comes to being kind.
Subjects were told they would be taking part in an experiment and instructed to sit in the waiting room while everything was being set up - unaware they were already under observation.
While they eagerly awaited what was going to happen next, an actor posing as a production assistant, started to tidy up and ‘accidentally’ knocked over a pot of pens to see how the volunteers would react.
The differences between the adults and children are immediately obvious, as the kids go to help clear up the felt-tips without question - whereas the grown-ups were more hesitant.
Child psychologist, Dr Richard Woolfson, said: “The results of the experiment confirm that children feel more comfortable with others who are caring and kind, because experience has taught them that kindness creates a better atmosphere than conflict at home, and cooperation gets better results.
"Once they leave the sheltered world of childhood, and enter adulthood, however, they may find that priorities change, that results are valued more than people, and that success is valued more than sensitivity.
"In that harsher environment, kindness becomes less important, and may even be construed as a weakness.
"This may explain why the adults who took part in the experiment were less helpful than their children.”
The study also found 57 per cent of adults said children teach them how to be kind.
Among the most common good deeds carried out by adults on a regular basis are opening doors for strangers, with 56 per cent claiming to do this in a typical week,
Making tea for others (45 per cent) and smiling at a stranger (42 per cent) are also among the kind acts many commit.
But being charitable ranked low on the list, with just one in five adults checking in on an elderly neighbour, and just 17 per cent putting some time aside for volunteering.
When it comes to kids, sharing snacks is the most common act of kindness along with asking someone if they are OK and giving others a hug for no reason.
It also emerged that being nice is a natural mood-enhancer, with 52 per cent of adults saying they feel better after an act of kindness, while 28 per cent admit it gets them out of a bad mood.
Children also feel the benefit, with half feeling happier after being kind, and more than a third saying it has improved their day.
This content feeling might be why children surround themselves with like-minded individuals, with 86 per cent of youngsters placing importance on their friends also being kind.
And nine in 10 adults and children agreed good will is an important attribute to have.
The study, commissioned via OnePoll, also revealed adults place more emphasis on children being caring towards others, with 68 per cent saying this would make them prouder than their child getting good results at school.
Dr Richard Woolfson, said: ‘Children are innately more kind than adults.
"That’s why babies cry when they hear the stressed cries of another baby, and that’s why your toddler comforts his tearful friend, perhaps by giving him a cuddly toy to ease his unhappiness.
"These wonderful acts of kindness happen without any coercion and they are lovely to observe."