non-biological explanation for SZ

• how do cognitive deficit theories explain SZ

  explain SZ as an attentional impairment

  • we normally select and filter incoming stimuli and process it to extract meaning
  • filtering and processing systems are defective in brains of people with SZ and they let too much irrelevant information which means they are overwhelmed with external stimuli because they cannot interpret this appropriately so experience the world differently
• hemsley (1993) explanation for SZ - what did he suggest

  SZ may be caused by a failure to activate schemas

  • suggested that central deficit in SZ is a disconnection between stored knowledge and new sensory input
• hemsley (1993) explanation - what did he suggest with schemas

  • schema - packages of information stored in memory based on past experiences so when we encounter one of these, we don't have to pay attention to every detail
  • hemsley suggested that because this processing breaks down in SZ, they are subjected to sensory overload & don't know what aspects need their attention and which don't so SZ place importance to insignificant events so explains why they have delusions, paranoid episodes & disorganised thinking as they misinterpret events around them
• example of schizophrenic with failure to activate schemas

  SZ person cannot access schema, they sees people laughing and talking and pays attention to this behaviour leading to delusions such as 'they're making fun of and laughing at me'
• frith explanation - what did he suggest

  • SZ caused by faulty cognitive processes
  • people with SZ are unable to distinguish between actions that are brought about externally and internally
• frith explanation - why does this occur

  • SZ have problems with self-monitoring so fail to keep track of their own intentions - as a result, they mistakenly regard their own thoughts as external leading to auditory hallucinations
  • suggested that failure in self-monitoring could explant why SZ may think their movements are being controlled externally (e.g: internal process of arm movement, interprets process as delusions like 'someone is controlling my arm')
• frith explanation - theory of mind

  • suggested SZ may not have a theory of mind - the ability to understand what other peoples thoughts or intentions may be which could explain delusions and paranoid symptoms
• strength

  • research evidence suggesting SZ do misinterpret internal processes
  • mcguigan (1966) found the larynx of patients with SZ was active during the time they claimed to be experiencing auditory hallucinations
  • this suggests that SZ patients mistook their own inner speech for that of someone or something else
• weakness

  • unlikely that deficits in cognitive processing can fully explain cause of SZ, it's likely that cognitive deficits are caused by biological factors
  • beck (2009) found that there is an effect of dopamine reduction on 'cognitive loading' meaning that reduced levels of the NT cause the brain to struggle more in processing information suggesting that a pre-existing biological risk factor which affects the persons cognitive ability exists
  • although focusing on cognitive explanations for SZ, separating the biological factors is not easy and explanation may be rooted in biology
• strength

  • research evidence suggesting SZ patients may have cognitive deficits, misinterpreting internal processes
  • mcguire (1966) conducted PET scans comparing SZ patients with and without hallucinations against controls & found that activation of the brain areas (left middle temporal lobe) associated with internal speech monitoring were much lower in hallucination prone subjects
  • demonstrates SZ patients struggle to distinguish their own thoughts due to perceptual problems
• weakness

  • cognitive explanations may be an effect rather than a cause of SZ
  • hemsleys failure to activate schema is logical but doesn't tell us what causes the failure of schemas to be activated
  • therefore, cognitive explanation does not fully explain SZ as it does not account for the cause of it