Babies younger than 18 months have a primitive long-term memory lasting at least four months, but their recall is faulty, a study suggests.

Fourteen of 32 babies who had played with a puppet four months before remembered it had a removable mitten, but only two apparently recalled that the mitten had contained a tasty treat, researchers said.In a similar way, people may retain early preferences and tastes without recalling the experiences that formed them, said Cornell University researchers Katharine Cutts and Stephen Ceci.

In the study, infants between the ages of 8 and 18 months were encouraged to play with a puppet 15 minutes a day, five days a week, for three weeks.

They quickly learned that if they removed the mitten they would find a treat, Cutts said in an interview.

Then, the puppet was removed for four months. When children were re-introduced to it, they were given five minutes to play with it to see if they removed the mitten.