 - Patients: Patient participants will be excluded if they meet any of the following criteria: co-morbid DSM-IV TR Axis I disorder; current treatment with clozapine; total PANSS score 65, reflecting an acute psychotic episode; current history of drug abuse or dependence; history of head injury resulting in loss of consciousness; diagnosis of epilepsy or any other neurologic disorder; electro-convulsive therapy ECT treatment within the previous year; significant cardiac illness; or extrapyramidal symptoms EPS resulting in movement disorders which could affect ERP recordings. Additionally, as is common in caffeine research, participants will be excluded if they work night shifts or do not report normal i.e. nocturnal sleep patterns during screening 