Malingering is defined as the intentional production of false or grossly exaggerated physical or psychological symptoms motivated by external incentives. In a criminal-justice setting this can include fabricating psychiatric symptoms, exaggerating the extent of psychiatric symptoms and feigning mental disability. In a survey of forensic psychologists the prevalence of malingering was estimated at 17.4%. One test aimed at screening out malingerers is the Test of Memory Malingering which is designed to appear much more difficult than it actually is. Those who are not malingering score highly but those who are deliberately trying to score a low mark get a suspiciously low result. A recent trial on 21 mildly-retarded forensic patients in the U.S. has found that even people with a learning disability score more highly on the test than those who are deliberately trying to get a low score in an attempt to feign mental disability.
Simon, Michael J. - Performance of mentally retarded forensic patients on the Test of Memory Malingering Journal of Clinical Psychology April 2007, 339-344