Babies as young as six months can understand a wide vocabulary, contrary to traditional belief, scientists claim.

New research by psychologists suggests infants recognise basic words such as "apple" and "arm" twice as early as originally thought. Previously, it was believed children could not grasp the meaning of such words until they were at least 12 months.

The findings of the study were published in the Proceedings of the National Academy of Sciences journal. More than 30 children aged six to nine months were tested on their understanding of basic objects and were pitted against 50 children aged 10 to 20 months.

In the study, psychologists noticed the babies fixed their gaze on the noun named more than on other objects - too often to be a coincidence.

Dr Daniel Swingley, of the University of Pennsylvania, one of the psychologists who conducted the experiment, said: "I think this study tells parents: You can talk to your babies and they're going to understand a bit of what you're saying."