Murphy et al. investigated this further using a probabilistic reversal learning task in which subjects were faced with occasional negative feedback that was actually false. On each trial of the task subjects choose one of two stimuli on screen, one considered correct and the other incorrect, this is followed by feedback. Instructions prior to starting the task inform the subject that sometimes the rule will change and the previously correct stimulus will be incorrect, but sometimes the computer will give them incorrect feedback. They are instructed to switch responding only when they are sure the rule has actually changed. MDD subjects demonstrate intact acquisition and reversal of probabilistic learning but are impaired in their ability to maintain a response in the face of misleading negative feedback. This profile of impairment may be relatively specific to MDD as, for example, it is not found in subjects with other neuropsychiatric conditions. This 'abnormal response' to negative feedback may represent a significant link between negative affect and cognitive impairments in depression.