What do visual hallucinations tell us about the nature of consciousness
What do visual hallucinations tell us about the nature of consciousness?
The term ‘hallucination’ is difficult to define. There is a fine line between a ‘hallucination’ and an ‘illusion’. A hallucination differs from an illusion in that illusions are a product of misinterpretations of external stimuli whereas hallucinations need no such requirement making them an entirely internal process. A true hallucination can also be distinguished from a pseudo-hallucination in which the individual can recognise that what they’re seeing or hearing is not real. Hallucinations are also different from voluntary mental imagery, in that the thought has not uncontrollably forced itself onto our minds. Slade and Bentall (1988, cited in Blackmore, 2010) provided a working definition of a hallucination: “Any percept-like experience which (a) occurs in the absence of an appropriate stimulus, (b) has the full force or impact of the corresponding actual (real) perception, and (c) is not amenable to direct and voluntary control by the experiencer.” Hallucinations are frequently associated with schizophrenia. In result, those who hallucinate hesitate to come forward due to fear of being labeled crazy. The Society for Psychical Research’s ‘Census of Hallucinations’ is one of the first attempts to study hallucinations in the general population. 1684 people from 17,000 said they had previously suffered from a hallucination. It was found that visual hallucinations were more common than auditory hallucinations, and hallucinations where generally more common in females, with the most common type being a vision of a person (Blackmore, 2010).
One general model of hallucinations is the ‘neurophysiological dissociation’ theory proposed by Marrazzi (1962, as cited in Slade 1976). He found that LSD produced inhibition of the association areas without affecting the primary visual cortex. He proposed that hallucinogenic drugs have their effect by producing a functional dissociation between the
The term ‘hallucination’ is difficult to define. There is a fine line between a ‘hallucination’ and an ‘illusion’. A hallucination differs from an illusion in that illusions are a product of misinterpretations of external stimuli whereas hallucinations need no such requirement making them an entirely internal process. A true hallucination can also be distinguished from a pseudo-hallucination in which the individual can recognise that what they’re seeing or hearing is not real. Hallucinations are also different from voluntary mental imagery, in that the thought has not uncontrollably forced itself onto our minds. Slade and Bentall (1988, cited in Blackmore, 2010) provided a working definition of a hallucination: “Any percept-like experience which (a) occurs in the absence of an appropriate stimulus, (b) has the full force or impact of the corresponding actual (real) perception, and (c) is not amenable to direct and voluntary control by the experiencer.” Hallucinations are frequently associated with schizophrenia. In result, those who hallucinate hesitate to come forward due to fear of being labeled crazy. The Society for Psychical Research’s ‘Census of Hallucinations’ is one of the first attempts to study hallucinations in the general population. 1684 people from 17,000 said they had previously suffered from a hallucination. It was found that visual hallucinations were more common than auditory hallucinations, and hallucinations where generally more common in females, with the most common type being a vision of a person (Blackmore, 2010).
One general model of hallucinations is the ‘neurophysiological dissociation’ theory proposed by Marrazzi (1962, as cited in Slade 1976). He found that LSD produced inhibition of the association areas without affecting the primary visual cortex. He proposed that hallucinogenic drugs have their effect by producing a functional dissociation between the
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