Lemurs are so distantly related to humans they look more like cats
Scientists studying the human tendency to follow the gaze of other people have found a link to the behaviour of lemurs, a distant primate relative.
Psychologists at the University of St Andrews said the action was a practical, food-finding skill, dating back to the time of the first primates.
Previous studies of apes and monkeys found they could follow the direction of another's gaze.
But they failed to use the ability for a purpose such as locating nourishment.
Professor Richard Byrne said: "Humans find it impossible not to look up when they see someone staring upwards at the sky, even when they know it might be a trick.
"It's been known for some years that several species of non-human primates, apes and monkeys, show the same tendency.
"But when their ability to use this to find useful information, such as where food is hidden, has been tested, they generally failed."
Lemurs are primates so distantly related to humans they look more like cats than monkeys.
Fellow researcher April Ruiz explained that the discovery suggested the gaze ability had evolved earlier than first thought.
She said: "Because we have found this ability, once thought unique to humans, in lemurs, we can push back the date of its original evolution far beyond the last common ancestor we share with apes, or even with monkeys, back to the time of the first primates."
The researchers found that whenever a lemur looked at a location signalled by gaze, it was most likely to choose that location to search for food.
In contrast to previous tests with primates, the lemurs were able to use gaze to increase their chance of finding food.