Habitual tasks, like taking medicine every few hours, rely on "prospective memory". This type of memory, which appears to be impaired by schizophrenia, enables you to remember that you have to do something in the future, without being prompted.
Brita Elvevåg, from the Clinical Brain Disorders Branch of the National Institute of Mental Health and her colleagues who carried out the research, wrote: "To our knowledge this is the first study to show that schizophrenia is associated with an overall impairment in habitual prospective memory performance".
The authors hypothesised that patients with schizophrenia would have problems with tasks requiring prospective memory. They might mistake remembering they have to do something with remembering they've actually done it. Their hypothesis stemmed from the theory that people with schizophrenia confuse real and imagined events.
To test their hypothesis the researchers, based at NIMH and the University of Warwick, compared the prospective memory of people with and without the disease. In each test participants manoeuvred a ball around an obstacle course for 90 seconds. They were asked to turn over a counter when they were at least 25 seconds into the test. The time delay ensured that prospective memory had to be used. Participants with schizophrenia were more likely to forget to turn over the counter.
At the end of the test the participants were asked if they had remembered to turn over the counter. Approximately a third of the time participants with schizophrenia reported they had done so when they had not.