The old adage "sticks and stones can break your bones, but words can never hurt you", simply is not true, according to researchers. Psychologists found memories of painful emotional experiences linger far longer than those involving physical pain.

They quizzed volunteers about painful events over the previous five years.

Writing in the journal Psychological Science, they said evolutionary brain changes which allow us to work better in groups or societies could be key.

The volunteers, all students, were asked to write about painful experiences, both physical and emotional, then given a difficult mental test shortly afterwards.

The principle was that the more painful the recalled experience, the less well the person would perform in the tests.

Test scores were consistently higher in those recalling physical rather than "social" pain.

Psychological scoring tests revealed that memories of emotional pain were far more vivid.

Social evolution

Researcher Zhansheng Chen, from Purdue University in Indiana, said that it was much harder to "re-live" physical pain than to recall social pain.

He said the evolution of a part of the brain called the cerebral cortex, which processes complex thinking, perception and language, might be responsible.

He said: "It certainly improved the ability of human beings to create and adapt, to function in and with groups, communities and cultures, and to respond to pain associated with social interactions.

"However, the cerebral cortex may also have had an unintended effect of allowing humans to relive, re-experience and suffer from social pain."

The researchers now plan to repeat the experiment in older people, who are more likely to have experienced chronic pain.

Michael Hughesman, a child psychologist based in Germany, agreed that it was likely that emotional pain was handled in a different part of the brain from physical pain, and likely to be longer-lasting.

He said: "There is something very intangible about emotional damage - with physical pain, you can see the bruise, but in emotional abuse there is often fear and anxiety which remains.

"If someone tells you in the playground that they are going to get you after school, then you tend to be anxious and afraid about it far more than if someone just punches you there and then."