Previous research had found that rhesus monkeys consistently failed in an important test of self-awareness, the ability to recognise themselves in a mirror but, like apes and dolphins, they did seem to be able to monitor their own mental states.

And according to a new research, scientists now believe the animals have a sense of "self-agency" which traces thoughts and actions to the existence of "me".

For the new study, scientists got 40 university students and four trained male rhesus monkeys to move a computer cursor with a joystick. As they were doing this, a second "distractor" cursor partially matched their movements.

Both humans and monkeys were asked to identify which computer cursor was being moved by them and responding to their intentions. In both cases, they were able to select the cursor they controlled at greater than chance levels.

"This suggests that the monkeys, like humans, have some understanding of self-agency," said psychologist Justin Couchman, from the University at Buffalo in the US, who led the research. "This awareness, or implicit sense that it is 'me' who is presently executing a bodily movement or thinking thoughts, is an important form of self-awareness."

The study, reported in the Royal Society journal Biology Letters, may improve understanding of self-awareness problems in people with conditions such as autism, schizophrenia and Alzheimer's disease.

"Mirror self-recognition is developmentally delayed in autistic children and absent in many who are mentally retarded, have Alzheimer's disease or are schizophrenic," said Mr Couchman.

"It is not clear why this deficit occurs, but like rhesus monkeys, these groups may simply have biases against mirrors.

"If, when studied, such individuals attempted to distinguish self-generated actions from partially altered actions in the paradigm reported in this study, it might offer information as to whether the breakdown in their mirror self-recognition is due to a difficulty in processing certain kinds of perceptual or cognitive information."