<P> Schizophrenia is often described in terms of positive and negative (or deficit) symptoms . Positive symptoms are those that most individuals do not normally experience, but are present in people with schizophrenia . They can include delusions, disordered thoughts and speech, and tactile, auditory, visual, olfactory and gustatory hallucinations, typically regarded as manifestations of psychosis . Hallucinations are also typically related to the content of the delusional theme . Positive symptoms generally respond well to medication . </P> <P> Negative symptoms are deficits of normal emotional responses or of other thought processes, and are less responsive to medication . They commonly include flat expressions or little emotion, poverty of speech, inability to experience pleasure, lack of desire to form relationships, and lack of motivation . Negative symptoms appear to contribute more to poor quality of life, functional ability, and the burden on others than positive symptoms do . People with greater negative symptoms often have a history of poor adjustment before the onset of illness, and response to medication is often limited . </P> <P> Deficits in cognitive abilities are widely recognized as a core feature of schizophrenia . The extent of the cognitive deficits an individual experiences is a predictor of how functional an individual will be, the quality of occupational performance, and how successful the individual will be in maintaining treatment . The presence and degree of cognitive dysfunction in individuals with schizophrenia has been reported to be a better indicator of functionality than the presentation of positive or negative symptoms . The deficits impacting the cognitive function are found in a large number of areas: working memory, long - term memory, verbal declarative memory, semantic processing, episodic memory, attention, learning (particularly verbal learning). Deficits in verbal memory are the most pronounced in individuals with schizophrenia, and are not accounted for by deficit in attention . Verbal memory impairment has been linked to a decreased ability in individuals with schizophrenia to semantically encode (process information relating to meaning), which is cited as a cause for another known deficit in long - term memory . When given a list of words, healthy individuals remember positive words more frequently (known as the Pollyanna principle); however, individuals with schizophrenia tend to remember all words equally regardless of their connotations, suggesting that the experience of anhedonia impairs the semantic encoding of the words . These deficits have been found in individuals before the onset of the illness to some extent . First - degree family members of individuals with schizophrenia and other high - risk individuals also show a degree of deficit in cognitive abilities, and specifically in working memory . A review of the literature on cognitive deficits in individuals with schizophrenia shows that the deficits may be present in early adolescence, or as early as childhood . The deficits which an individual with schizophrenia presents tend to remain the same over time in most patients, or follow an identifiable course based upon environmental variables . </P> <P> Although the evidence that cognitive deficits remain stable over time is reliable and abundant, much of the research in this domain focuses on methods to improve attention and working memory . Efforts to improve learning ability in individuals with schizophrenia using a high - versus low - reward condition and an instruction - absent or instruction - present condition revealed that increasing reward leads to poorer performance while providing instruction leads to improved performance, highlighting that some treatments may exist to increase cognitive performance . Training individuals with schizophrenia to alter their thinking, attention, and language behaviors by verbalizing tasks, engaging in cognitive rehearsal, giving self - instructions, giving coping statements to the self to handle failure, and providing self - reinforcement for success, significantly improves performance on recall tasks . This type of training, known as self - instructional (SI) training, produced benefits such as lower number of nonsense verbalizations and improved recall while distracted . </P>

What is the most common symptom of schizophrenia