Psychologists have discovered that children are likelier to try foods that they do not normally like if they see adults smiling while they eat them.

Children as young as five were more willing to taste vegetables they had previously rejected if they saw an adult savouring them.

The findings suggest that youngsters' immature brains are susceptible to the emotions of others, the Telegraph reported.

Simply seeing enjoyment on the face of an adult might trigger the same feelings in a part of their brains called the prefrontal cortex.

The World Cancer Research Fund said that 80 per cent of children in England eat less than the recommended five portions of fruit and vegetables a day, increasing their risk of cancer.

Boys aged five to 15 on average consume 3.1 portions of fruit and vegetables a day and girls 3.3 portions.

Parents often deploy a variety of tactics to encourage them to eat vegetables, from playing games with food to exaggerating their own enjoyment of them.

But the latest research suggests simply smiling while eating could be the key.

Experts at the French National Institute for Agricultural Research in Paris recruited children aged five, eight and a group of adults.

The psychologists assessed their reactions to photographs of women eating various foods, including some that the volunteers said they did not like, including vegetables.

The researchers said the findings might have important implications for the encouragement of children's healthy eating habits.

In a report on their findings, the researchers said: "Adults may unconsciously influence children's food preferences via their facial expressions of pleasure or disgust."