Negative symptoms are those conspicuous by their absence—lack of concern for one's appearance, and lack of language and communication skills, for example.
Schizophrenia is a severe mental illness characterized by a range of behaviors, including hallucinations and delusions.
Hallucinations refer to disorders involving the sensory systems, and are most often manifested as seeing or hearing things (e.g., voices) that do not exist.
Other symptoms of schizophrenia include bizarre behavior, odd posture or movements, facial grimacing, loss of, or indifference to self-help skills (grooming, washing, toileting, feeding, etc.).
Several measures or rating scales have been developed to assess the positive and negative aspects of schizophrenia.