Schizophrenia symptoms fall into two categories: positive and negative symp­toms. Positive symptoms are behaviours or experiences outside the normal range of human activities. Hearing voices is a good example. Negative symp­toms are behaviours that are removed from the normal range. A reduced ex­perience of pleasure is a good example. Positive symptoms are prominent during the ‘active’ phase of the illness, when an affected individual is most disturbed and disruptive. The active phase is the phase that will more often lead to the individual’s referral for care. This is often because the affected individual will be doing or saying things that upset or disturb people around them, or at least get their attention and draw concern. For example, an individual with delusions might complain to her spouse that she is being followed by aliens and demandthat he help her find a way to stop them. Negative symptoms are most visible during the ‘prodromal’ and ‘residual’ phases of the illness. The prodromal phase comes before the first active phase (so actually occurs before a diagnosis of schizophrenia is ever made), and a residual phase follows each active phase.This class of symptoms most often includes delusions and auditory, visual, or other sensory hallucinations. Positive symptoms can be divided into percep­tual (i.e., affecting perception, or the ability to become aware of some stimulus through the senses), cognitive (i.e., impacting ways of thinking), emotional, or motor (physical) signs. Because these symptoms are so easy to recognize, even to the untrained eye, they make up a large part of the layperson’s general view of schizophrenia.Auditory hallucinations are the most common perceptual problems seen in schizophrenia. Many times, these hallucinations take the form of a voice, some­times making a running commentary on the individual’s thoughts or behaviours. Sometimes they take the form of several voices, each talking with the other. Some individuals with schizophrenia have visual, olfactory (i.e., affecting the sense of smell), or gustatory (i.e., affecting taste) hallucinations, but these are rare. Somatic hallucinations may also occur, in which the altered perception centres at or on the body’s organs.