An over-reliance on using computers and search engines is weakening people's memories, according to a study.
It showed many people use computers instead of memorising information.
Many adults who could still recall their phone numbers from childhood could not remember their current work number or numbers of family members.
Maria Wimber from the University of Birmingham said the trend of looking up information "prevents the build-up of long-term memories".
The study, examining the memory habits of 6,000 adults in the UK, France, Germany, Italy, Spain, Belgium, the Netherlands and Luxembourg, found more than a third would turn first to computers to recall information.
But the survey suggests relying on a computer in this way has a long-term impact on the development of memories, because such push-button information can often be immediately forgotten.
"Our brain appears to strengthen a memory each time we recall it, and at the same time forget irrelevant memories that are distracting us," said Dr Wimber.