Term	Explanation
Delusion	A fixed implausible, preoccupying belief, such as that a microchip has been implanted behind the ear and is controlling their thoughts
Hallucination	A voice, vision or other percept in the absence of a stimulus. In schizophrenia these characteristically take the form of voices commenting on the sufferer’s actions
Passivity delusions	Delusions that an external agency is controlling thoughts, actions or perceptions
Positive symptoms	Psychotic symptoms such as delusions and hallucinations
Prediction error	Used in computational models to describe the mismatch between what is expected and what actually happens that drives learning
Psychosis	A syndrome characterised by one or more of the following symptoms: delusions, hallucinations, thought disorder, catatonia
Psychotic disorders	Schizophrenia is the most common psychotic disorder, but psychosis is also seen in bipolar and unipolar affective disorders
Negative symptoms	Symptoms such as apathy, reduced social interactions, poor self-care
Schizophrenia	A chronic mental illness characterised by persistent psychotic and negative symptoms and relatively subtle cognitive impairment.