Present And Future Directions

The four approaches of experimental cognitive psychology, cognitive neuropsychology, cognitive science, and cognitive neuroscience differ in their strengths and weaknesses. As a result, what is needed in order to maximise our understanding of human cognition is to use the method of converging operations. This method involves making use of a variety of approaches to consider any given issue from different perspectives. When this method is applied with two approaches, there are two possible outcomes:

1. The findings obtained are broadly comparable.

2. The findings differ significantly.

When the findings from two approaches are similar, this increases our confidence in the validity of the findings and in the usefulness of both approaches. When the findings are dissimilar, this indicates the need for further research to clarify what is happening. Thus, the method of converging operations can help to prevent researchers from drawing incorrect conclusions on the basis of limited findings from a single approach.

There are various examples in this book of cases in which the method of converging operations has produced comparable findings from different approaches. For example, there is the issue of whether implicit memory should be divided into perceptual and conceptual implicit memory (considered earlier in the chapter). PET studies have indicated that visual perceptual priming affects the bilateral occipito-

temporal areas, whereas conceptual priming affects left frontal neocortex (see Chapter 7). The distinction between perceptual and conceptual priming is also supported by research within cognitive neuropsychology. Intact perceptual priming but impaired conceptual priming is shown by Alzheimer patients, and the opposite pattern is shown by patients with right occipital lesions (see Chapter 7).

Some cases in which the findings from two approaches are different have been discussed in this chapter. Such differences are probably most common when findings from cognitive neuropsychology and cognitive neuroscience are compared. There is a general tendency for the cognitive neuropsychological approach to underestimate the brain areas necessary to perform a given cognitive function, whereas the cognitive neuroscience approach tends to overestimate them. An awareness of these tendencies makes it easier to reconcile the findings of cognitive neuropsychology and cognitive neuroscience.

Rugg (1997) has identified some of the key ways in which the present approach to human cognition differs from those used in the past. As he pointed out, the historical emphasis within cognitive psychology, "is placed on models of cognitive function that make no reference to their possible biological substrates, and the idea that biological data might constrain or inform functional models is treated with scepticism" (Rugg, 1997, p. 5). In contrast, the current (and probably future) approach is based on the following key assumption: "The mapping between physical activity in the brain and its functional state is such that when two experimental conditions are associated with different patterns of neural activity, it can be assumed that they have engaged distinct cognitive functions, this assumption opens the way for physiological data to play a role in the development of functional models of cognition" (Rugg, 1997, pp. 5-6).

Marr (1982) provided a more complete theoretical framework. According to him, information-processing theories should be characterised at three levels (see Table 19.2). The computational level contains a specification of what needs to be computed for a given task to be carried out. It is also concerned with the purpose or function of the computation. At the algorithmic level, the exact nature of the computation is specified. This level should capture the detailed processing steps that intervene between the inputs and outputs, and it should take account of the mechanisms people actually use. Finally, the hardware level is the brain. The brain imposes limitations on the kinds

Exploring EFT

Exploring EFT

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