Advantages of the experiment method include the fact that the experiments, variables and conditions can be replicated. Further benefits of experiments are control and accuracy. Another advantage is causation; this is being able to identify specific causes for specific events. However this can also be seen as a disadvantage as human behaviour is rarely dependant on a single cause. Another disadvantage is the specific control of experiments, this can lead to inaccurate or unnatural data, or production of artificial conditions, rather than naturalistic ones, which then leads to artificial behaviour. This is probably the biggest disadvantage to experimentation as often the subject can act in a way he or she believes is expected rather than how he or she would act naturally. This phenomen is often referred to as the expectancy effect, leading to unnatural behaviour and distorted results(Best, 1999). This criticism can sometimes be countered by observing people in their natural enviornment.
However, this can have its own disadvantages for example the researcer may be subdued by the subject/s and may not record the information as accurately as under controlled circumstances. Also the researcher cannot plan to investigate a certain aspect of behaviour as there is no way to make anything occur as there are no variables and the researcher must stay uninvolved, therefore the data collected may be of no relevance to the hypothesis or ideas of the psychologist(Eysenck 2000).
All these criticsims aside the biggest problem faced by experimental psychologist is that most theories put forward by them often only provide us with a window on the active systematic mental processes that underlie all other mental activity.
Cognitive neuropsychology
Cognitive neuropsychology on the other hand attempts to reveal the patterns of cognition in the brain by the means of studying patients with abnormal brain functions (Plaut, 1995). Within the field of cognitive neuropsychology the prevalent hypothesis is that brain is composed of relatively independent components, or modules, and that these subsystems perform particular functions, which can due to brain damage be selectively injured (Plaut, 1995).
Alternative nonmodular theories emphasize the brain to be operating 'as a whole', like a 'uniform general purpose system' (Bechtel & Graham, 1998).
Between the debates of modularity and homogeneity, neuropsychologists have got a powerful counter argument: the occurrence of double dissociations, which are traditionally interpreted as offering strong evidence about the modularity of mind, and therefore they are the essence of theorizing in cognitive neuropsychology (Plaut, 1995).
A double dissociation is manifested when patients suffer brain impairment with the reversed pattern of deficits from each other. The underlying logic here is that these cognitive functions are psychologically and anatomically separate and distinct, because if they were not, the brain damage should then disrupt both functions equally (Ashcraft, 2002).
We shall now continue to explain the concept of a double dissociation with a concrete demonstration of the phenomenon. Thus we shall contrast two types of aphasias (disruption of language): Broca's and Wernicke's aphasias, as they together offer an excellent example of a double dissociation. Broca's aphasia (or non fluent aphasia) is typically characterized by disrupted speech production, disrupted syntax, but spared semantics (Ashcraft, 2002). Hence Broca's aphasics are able to understand language, but their speech is extremely clumsy, mainly consisting of two word utterances with only a few if any reference to grammar (Ashcraft, 2002;).
Impairment in motor word production cannot be induced by brain damage in any other area, which seems to offer evidence that the cognitive function is localized (Ashcraft, 2002). However, there are other possible explanations as well. One could argue, that Broca's area, rather than being independent, is a part of a hierarchical system of relationships, and damage to this area contributes other parts in the systems to receive insufficient or wrong inputs, leading the whole system to fail in a particular cognitive task (in this case the production of speech) (Bechtel & Graham, 1998). Moreover, it could be that with a single dissociation one task is simply harder than another one.
However if we look at Wernicke's aphasia (or fluent aphasia) whose symptoms are almost like a mirror reversion of the complaints associated with Broca's aphasia, and this pattern of complimentary deficits is precisely the basis for a double dissociation. Unlike in Broca's aphasia, in Wernicke's aphasia language comprehension and semantics are disrupted while as speech production is spared (Ashcraft 2002): The flow of speech is effortless for a patient with Wernicke's aphasia, but s/he is unable to retrieve the right word and consequently s/he produces nonsensical 'wordsalads' with very little meaning (Bechtel & Graham, 1998). Thus, through impairment in different areas of the brain, patients show the opposite pattern of deficits to each other. In this way the double dissociation cancels out the basis of the claims that the test results could be explained in terms of task difficulty, and Broca's and Wernicke's aphasics provide strong evidence that speech production and comprehension are separately functioning components (Ashcraft 2002).
However, Martin (2003) emphasizes that these traditional views of language representations are oversimplified. The suggestion that motor word representations are localized in Broca's area and auditory words in Wernicke's area, do not provide a valid understanding of the underlying reasons in language syndromes, and cannot capture the complicated nature of language representation in the human brain (Martin, 2003). For example, it has been argued that there are a number of possible underlying reasons that can give rise to the poor comprehension typical for Wernicke's aphasics, including a disruption of phoneme identification, a disruption of phonological word forms, or a disruption of semantics (Martin, 2003). He also points out that studies during the 1970s & 1980s revealed that some Broca's aphasics showed poor comprehension when testing their understanding of a complex syntactic information in a sentence, which obviously cannot be explained in terms of a disrupted motor word production.
This uncovers the very heart of the problems in double dissociation studies: It is extremely difficult to find patients with districted impairments; patients who have a lesion that is limited into a single component. Instead, brain damage is usually extensive, affecting different cognitive systems to a greater or lesser extent (Plaut, 1995).
The lesion method is not particularly good when studying interactions between brain regions (Bechtel & Graham, 1998). However, through the availability of new functional brain imaging techniques, the field of cognitive neuropsychology is in the middle of a fascinating period, which hopefully leads into a greater insight of the patterns of cognition in the human brain, thus perhaps resolving some of the question marks between modular and nonmodular theories (Kimberg, 1993).
Conclusion
It is very important to note at this point that the relationship between these two methods is not of rivalry but of cross-fertilisation, a very good example of this can be seen by looking at Atkinson and Shiffrin’s model of memory. Atkinson and shiffrin where experimental psychologists who came up with a model explaining the structures and processes involved in memory. Many cognitive psychologists have used this model as the starting point to their theories, including several cognitive neuropsychologists. However the model was often seen to be simplistic and after years of reasearch cognitive neuropsychologists have been able to improve upon it giving us a better understanding of the processes involved in memory (Eysenck, 2000; Best, 1999; Baddely, 1990). In other words, the development so far (with regards to understanding the memory process) has been in the form of a two part process with both methods playing an equally important role.
Cognitive psychology (1967)
Plato himself used the term soul however numerous academics and specially scientists have reinterpreted it as referring to the mind.
In other words more information can be obtained to prove or disprove the hypothesis posed by the psychologist
Commonly known as natural observation
this opinion was first voiced by Wilhelm Wundt (1832-1920) who decided to divide the subject matter of cognitive psychology into two classes arguing that higher mental processes such as thinking, could not be studied successfully using the fairly limited observational technique of the laboratory (Leahey 1987).
That is if one patient has dysfunctional cognitive ability A, but spared ability in cognitive function B, then the other patient demonstrates the opposite pattern with inability to perform cognitive function B and at least a relatively intact ability to perform function A (Ashcraft, 2002).
Broca's area is located in the anterior lateral portion of the left hemisphere of the brain, which lies adjacent to the motor projection areas related to speech, thus explaining the disrupted motor word production in Broca's aphasia (Ashcraft 2002).
For example, it could be that the lesion has damaged both cognitive representations equally, such as speech production and comprehension, but it is more difficult for a patient to produce speech than to comprehend it (Plaut, 1995). However, if a double dissociation is manifested, it undermines the basis for these claims.
Wernicke's aphasia may be caused by a lesion in the auditory primary projection area of the left temporal and parietal lobes, which has been interpreted to affect sensory word representations, hence giving rise to the disrupted comprehension (Martin, 2003).
For example the research done by Warrington and Shallice in 1974 on KF a patient who suffered damage in the left Parieto-occipital region of the brain following a motorcycle accident. (Eysenck, 2000)
