Dr Matthew Gage, from the University of East Anglia, who carries out research into sperm function in animals, said it was highly unlikely that sperm were capable of any form of cognitive thought.

BBC: Sperm 'have sense of direction'

If you have an aging parent or loved one with any form of mild cognitive impairment, early dementia or other disease that affects thinking and judgment, here are seven basic things family can do to reduce the risks of ripoff.

FORBES: Are Our Aging Parents Sitting Ducks?

For decades, psychologists have debated whether narcissism is a form of self-delusion, a cognitive bias, or a self-serving social strategy.

FORBES: Study: Narcissists Know What You Think of Them and They Don't Give a Flying Fig

Three had suffered from mild cognitive impairment - a more severe form of memory loss than that associated with ageing but less severe than Alzheimer's.

BBC: Clue to old age memory loss