Ultradian rhythms -  Biological cycles that occur more than once a day.

Unconditional positive regard -  A therapist quality that is considered crucial in client-centered therapy. It involves nonjudgmental acceptance of the client.

Unconditioned response -  A naturally occurring response that happens without previous conditioning.

Unconditioned stimulus -  A stimulus that evokes an innate response.

Unconscious -  The part of the mind that contains thoughts, feelings, desires, and memories of which people have no awareness but that can influence people’s behavior.

Undifferentiated type -  A subtype of schizophrenia diagnosed if a patient does not meet criteria for paranoid, disorganized, or catatonic subtypes of schizophrenia.

Unstable attribution -  An inference that an event or behavior is due to unstable, temporary factors.