Paranoid schizophrenics may not use irrelevant signals. The use of measures of blocking and of urinary dopamine.

Conditioned blocking tests for the use of superfluous (irrelevant) information in task-solving. Paranoid psychotic, obsessive-compulsive and healthy subjects usually showed normal blocking, but non-paranoid subjects tended to learn about the superfluous stimulus. Attenuated blocking was usually associated with increased dopamine utilization measured in 24h urine samples. This may reflect poor stabilization of response to neuroleptic medication.