Anhedonia: Inability to experience pleasure due to impairment or dysfunction of normal psychological and neurobiological mechanisms. It is a symptom of many PSYCHOTIC DISORDERS (e.g., DEPRESSIVE DISORDER, MAJOR; and SCHIZOPHRENIA).Pleasure: Sensation of enjoyment or gratification.Affective Symptoms: Mood or emotional responses dissonant with or inappropriate to the behavior and/or stimulus.Schizotypal Personality Disorder: A personality disorder in which there are oddities of thought (magical thinking, paranoid ideation, suspiciousness), perception (illusions, depersonalization), speech (digressive, vague, overelaborate), and behavior (inappropriate affect in social interactions, frequently social isolation) that are not severe enough to characterize schizophrenia.Happiness: Highly pleasant emotion characterized by outward manifestations of gratification; joy.Schizoid Personality Disorder: A personality disorder manifested by a profound defect in the ability to form social relationships, no desire for social involvement, and an indifference to praise or criticism.Schizophrenic Psychology: Study of mental processes and behavior of schizophrenics.Philosophy: A love or pursuit of wisdom. A search for the underlying causes and principles of reality. (Webster, 3d ed)Reward: An object or a situation that can serve to reinforce a response, to satisfy a motive, or to afford pleasure.Affect: The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves.Irritable Mood: Abnormal or excessive excitability with easily triggered anger, annoyance, or impatience.Depressive Disorder, Major: Marked depression appearing in the involution period and characterized by hallucinations, delusions, paranoia, and agitation.Depression: Depressive states usually of moderate intensity in contrast with major depression present in neurotic and psychotic disorders.Schizophrenia: A severe emotional disorder of psychotic depth characteristically marked by a retreat from reality with delusion formation, HALLUCINATIONS, emotional disharmony, and regressive behavior.Self Stimulation: Stimulation of the brain, which is self-administered. The stimulation may result in negative or positive reinforcement.Expressed Emotion: Frequency and quality of negative emotions, e.g., anger or hostility, expressed by family members or significant others, that often lead to a high relapse rate, especially in schizophrenic patients. (APA, Thesaurus of Psychological Index Terms, 7th ed)Psychiatric Status Rating Scales: Standardized procedures utilizing rating scales or interview schedules carried out by health personnel for evaluating the degree of mental illness.Food Preferences: The selection of one food over another.Motivation: Those factors which cause an organism to behave or act in either a goal-seeking or satisfying manner. They may be influenced by physiological drives or by external stimuli.Immobility Response, Tonic: An induced response to threatening stimuli characterized by complete loss of muscle strength.Psychometrics: Assessment of psychological variables by the application of mathematical procedures.Emotions: Those affective states which can be experienced and have arousing and motivational properties.Social Behavior: Any behavior caused by or affecting another individual, usually of the same species.Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.Mood Disorders: Those disorders that have a disturbance in mood as their predominant feature.Subliminal Stimulation: Stimulation at an intensity below that where a differentiated response can be elicited.Dysthymic Disorder: Chronically depressed mood that occurs for most of the day more days than not for at least 2 years. The required minimum duration in children to make this diagnosis is 1 year. During periods of depressed mood, at least 2 of the following additional symptoms are present: poor appetite or overeating, insomnia or hypersomnia, low energy or fatigue, low self esteem, poor concentration or difficulty making decisions, and feelings of hopelessness. (DSM-IV)Psychotic Disorders: Disorders in which there is a loss of ego boundaries or a gross impairment in reality testing with delusions or prominent hallucinations. (From DSM-IV, 1994)Depressive Disorder, Treatment-Resistant: Failure to respond to two or more trials of antidepressant monotherapy or failure to respond to four or more trials of different antidepressant therapies. (Campbell's Psychiatric Dictionary, 9th ed.)Social Behavior Disorders: Behaviors which are at variance with the expected social norm and which affect other individuals.Behavior, Animal: The observable response an animal makes to any situation.Connectome: A comprehensive map of the physical interconnections of an organism's neural networks. This modular organization of neuronal architecture is believed to underlie disease mechanisms and the biological development of the CENTRAL NERVOUS SYSTEM.