Conditioned blockingnext term (CB) refers to a delay in learning that a new stimulus, added during learning, has the same consequences as the previous termconditionednext term stimulus already present. In animals such “learned inattention” depends on monoaminergic and limbic function and, thus, CB performance should be informative on selective information processing impairments found in subgroups of psychotic previous termpatients.next term Attenuated CB in acute schizophrenia has been reported to normalize rapidly. This study examines in young previous termpatientsnext term the specificity of CB performance to illness, and its associations with symptoms, personality traits and monoaminergic metabolic status. CB was attenuated in psychotic previous termpatients with non-paranoidnext term symptoms (NP: n = 12, mean age 17 years) with respect to previous termobsessive-compulsivenext term (OCD: n = 13, mean age 16 years) and healthy subjects (CON, n = 29, mean age 18 years), but only a transient attenuation was observed in previous termparanoidnext term hallucinatory previous termpatientsnext term (PH: n = 14, mean age 19 years). Outgoing personality traits in CON and OCD subjects correlated with CB. In NP previous termpatientsnext term attenuated CB was associated with increasing neurotic lability. In PH previous termpatientsnext term CB correlated positively with “manic” but negatively with psychotic or neurotic scores. The severity of negative symptoms in previous termpsychosisnext term and specific negative/positive symptoms in the NP/PH groups was associated with reduced CB. Increased dopamine activity (24-h urine samples) correlated positively with CB, but relative increases of noradrenaline metabolism in NP and serotonin metabolism in OCD previous termpatientsnext term interfered. In summary, marked psychotic or neurotic traits and some symptom-states were associated with reduced CB. The particular selective processing problems of NP previous termpatientsnext term may reflect inappropriate NA activity.