Researchers said even they were surprised when they realised the secret of how recollections are created and stored.

They found that the brain "doubles up" by simultaneously making two memories of events.

One is for the present and the second is for the long-term, they found.

It had been thought that all memories start as a short-term memory and are then slowly converted into a lifetime version.

Experts said the findings from MIT in the US and a team from Japan were "beautiful and convincing".

Two parts of the brain are involved in collecting and storing personal experiences.