How can therapists differentiate between schizoid personality disorder and the negative symptoms of psychosis?

GOOD question.: Schizoid PSTY sufferers generally don't like being with other, are "drifter" types and like to wander around, usually solo. They have odd behaviors sometimes, usually around social events. Psychotics aren't necessarily withdrawn socially, and their oddities are usually somewhat different--related more to delusions or hallucinations, which are not typical of Schizoids. Neg. Sx's are lethargy,

By asking: Schizoids will tell the therapist they are completely indifferent to interpersonal relationships and do not get lonely or depressed. Those with negative symptoms of psychosis may not have the seeming energy to relate to others or seem emotionally flat, but if asked, they will say (provided they are NOT hallucinating) that interpersonal relationships are indeed desired.