Pattern Recognition Model

Patel and her colleagues advocate pattern recognition as the normative mode for diagnostic reasoning. It seems more likely to appear in familiar cases and experienced clinicians (Patel & Groen, 1986). It relies on a conception of memory containing patterns (or schema) that are prototypes of data combinations (Boshuizen & Schmidt, 1995; Johnson et al, 1981). The instance (ie the specific patient) is matched against the known pattern stored in memory. If a match is achieved, the diagnosis is made. However, it is unclear how pattern recognition can work in cases, which are an incomplete 'match' for the pattern stored in memory. King & Bithell (1998) suggest that pattern recognition is associated with the identification of cues, although cues do not appear so clearly in Patel’s work. Pattern recognition appears akin to Rasmussen’s second direction of inference discussed earlier. Indeed, he states that formal reasoning may appear to be omitted by experts in simple cases.

Theories of pattern recognition originated from the Gestalt school of psychology and tend to imply a pictorial representation (Bainbridge, 1988). Whilst some aspects of a patient's problem may be represented visually (for example, signs observed by the therapist), not all aspects of the problem will be available in this form. In addition, an intrinsic weakness in this approach is its inability to represent the strategies employed by novices or by experts in unfamiliar, complex situations, where alternatives have to be clearly considered and evaluated. Thus, clinically, in straightforward cases, the experts may be able to identify patterns in patient data, which allow forward reasoning. However, novices would still experience difficulties, unless they have acquired the relevant pattern. As a mode of reasoning, pattern recognition cannot support even experts in unfamiliar situations or complex cases. Elstein et al (1989) found that forward reasoning, pattern recognition modes can be used in familiar situations, but that they are insufficient to deal with the complex, the unknown or the novices’ strategies.

There is also the problem of the patterns' description. Some may be better described in terms of knowledge, which would make them easier to recognise. In the presence of ambiguity or data that unfold over time, it has been noted that hypothesis testing is invoked (Barrows & Feltovitch, 1987). Since not all the information is available at the beginning, it is not available as a pattern. Even where the diagnosis is immediately obvious (as in the case of a patient with a fracture), the subtle patient specific nuances are not available. These may include the nature of the injury - a trivial injury, for example, could indicate an underlying condition, which alters the diagnosis and constrains the

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immediate and long term management. It can also be affected by the exact site and type of injury and the possible complications ensuing from the precise injury. Indeed, pattern recognition might be similar to the hypothesis generation stage. However, the diagnosis still needs testing to be confirmed.

3.5.2 2 Hypothetico-Deductive Model

Elstein, Shulman and Sprafka (in research first published in 1978) showed that there were four components identifiable during diagnosis by physicians. These components were cue acquisition, hypothesis generation, cue interpretation and hypothesis evaluation. Cue acquisition involves the information gathering stage, whilst cue interpretation evaluates the cues in the light of alternative hypotheses. On this view, the cues are equatable to facts gathered from the patient and appeared to contribute to the solution in three ways (Elstein & Bordage, 1988). They could confirm the hypothesis, disconfirm it or they could be non-contributory. Both successful and unsuccessful diagnosticians formulated and successively refined a limited (4±1) set of hypotheses, which contributed to the final diagnosis. The information collected from the patient appears to possess a fair amount of redundancy, presumably in an attempt to confirm the diagnosis by thorough investigation. If too many diagnostic hypotheses were generated, they would be reformulated to stay within this 4±1 parameter, probably in an effort to contain the processing requirements.

Elstein et al’s research showed that hypotheses were retrieved from long term memory, often based on very few cues. These hypotheses were generated (Joseph & Patel, 1990), even if the subjects were specifically instructed not to produce them. Elstein et al (1989) interpret this as implying that hypothesis generation is a "psychological necessity" g\\/en the complexities of the clinical context, the enormous amount of information, which could potentially be gathered, and the limitations of working memory. It is the quality of the hypotheses that appears to distinguish the expert from the novice (Norman, 1988). Boreham et al (1996) suggest that the strategy of hypothesis generation and testing ‘chunks’ the information, thus ensuring that information processing requirements do not exceed capacity especially in the less experienced. Emphasis on hypothesis generation and testing should mean that the problem space is searched for all the alternatives. However, this model does not necessarily imply a direction for the diagnostic inference, which could be based on moving from normal to abnormal function or from the general picture to the specific case (Rasmussen, 1993). Patel & Groen (1986) criticise the hypothetico-deductive model as a weak method characteristic of novices. The use of the term 'weak' is criticised by Elstein et al (1989) who suggest that (because it denotes a method used to deal with difficult problems) the term 'general method' would be more appropriate.

One aim of the original research sought to identify strategic differences between expert and less expert physicians (Elstein et al, 1989). However, the degree to which individual cases could be

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diagnosed appeared more dependent on the individual's mastery of a particular area. To further complicate the situation, clinicians might apply strategies successfully in one case, but with another case the same strategy would fail. Inconsistency across cases was noted and the differences appeared to be attributable more to the way the problem was represented than to generic strategies. Case specificity implies that the ability to diagnose is partly reliant on the content of the problem (Elstein et al, 1993) and raises the practical problem of how many case simulations would be required to assess a novice’s problem-solving skills. It remains unclarified but is, however, an important issue for the research described in this thesis.

The hypothetico-deductive model has two parts; that of hypothesis generation and testing. Higgs & Jones (1995piJ advanced the view that the generation of the hypothesis uses inductive reasoning, whilst testing implicates the use of deduction. Thus, once diagnostic hypotheses have been generated the evidence used in testing forms the substance of the justification of the eventual diagnosis. Ridderikhoff (1991) suggests that this method adopts a position half-way between induction and deduction, because it combines the creative act of generating the hypothesis with the logic of deductive testing. However, human beings tend to emphasise confirmation and verification and, therefore, he holds the hypothetico-deductive model to be an inductive way of reasoning. Certainly, deduction has not been emphasised in the literature (Boreham et al, 1996). In medicine, hypothesis testing is usually presented as an application of such deductive logic. Boreham et al (1996) present examples, but question whether deductive logic is the major form of reasoning in medicine, since both the premises and the conclusion must equate to true. If sufficient time and resources are available, then the data collection phase may be stringent enough to allow deduction to occur. However, on their view, in more constrained circumstances, where less data may be acquired about the problem, circumstantial evidence will be invoked to support the diagnosis.

Circumstantial evidence has been defined as that which "tends to confirm o r disconfirm by reasonable inference from circumstances which give the evidence its weight"(Carlson and Dulany; 1988). Because this type of evidence is (by definition) context linked, each part is interdependent with uncertain implications. Therefore, its weight in the final diagnosis is unknown. In the medical context, for example, such evidence could include information about the patient’s social circumstances or previous response to treatment. It is held to come into its own when diagnosis is attempted under conditions of uncertainty and requires the generation of a coherent story, which takes account of all the factors surrounding the patient. It cannot be modelled in terms of deductive logic, because the truth value of the premises and conclusions cannot be established. The information includes clues to forming this story, but the less experienced clinicians may experience difficulties, if they were unsure about how to interpret these clues.

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Stopping rules). Case-specific information is interpreted by using theories and procedures with argumentation as "the process of constructing lines of reasoning for some proposition about a specific case" (Fox et al, 1990). The process of argumentation was represented as formal logic and comprises identifying a focus, selecting a candidate decision and then advancing confirming or negating arguments (Huang et al, 1993). These arguments are weighed and the evidence is evaluated. If a decision cannot be reached (eg if the confirming and negating arguments are equal), then further evidence should be sought.

The hypothetico-deductive model was applied to Physiotherapy by Payton (1985) and Higgs and Jones (1995). Payton surmised that the reasoning processes were similar to those of the physicians. His work used retrospective protocols, since an audio-taped record was played back to the subjects following the initial examination. These protocols could have been affected by subsequent events. Jones (1992) and Higgs (1992) developed a model of clinical reasoning in manual therapy based on the hypothetico-deductive model (Barrows & Tamblyn, 1980; Elstein et al 1989). This model has been widely accepted within musculo-skeletal dysfunction and is becoming increasingly influential, although it does not appear to have been validated by empirical research. It is illustrated in Figure 3.2.

Figure 3.2 Model of Clinical Reasoning in Physiotherapy (Reproduced from Jones 19 92)

tn to fiT n lto n . REASSESSMENT PHYSICAL THERAPY INTERVENTION INITIAL CONCEPT and M ULTIPLE HYPOTHESES INFORM ATION PERCEPTION and INTERPR ETA TION

DECISION

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• m anagam ant • know ladga baaa

• o o g n ltlv a a k illa • m a t a c o g n lt lv a a k i l l a DATA COLLECTION • a u b ja c llv e i n ia r v l a w * p h y a lc a l a x a m ln a tlo n EVOLVING CONCEPT of tha PROBLEM (h y p o th a a a a m o d lfla d )

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This model could be an example of what Johnson (1983) terms “reconstructed reasoning”.

On this view, experts construct a model that appears plausible as a means of codifying what they know about problem solving. Such reconstructed methods of reasoning typically appear in the writings of the practitioner group and are validated by acclamation, because practitioners recognise them as sensible elegant descriptions of their problem solving methods. Certainly this version of the hypothetico-deductive model appears to have been so acclaimed and adopted. However, Johnson further points out that reconstructed methods of reasoning appear inadequate for novices, because they continue to make problem solving errors. This conclusion tends to cast doubt upon Higgs and Jones, since the model is intended to be used as a teaching aid. The hypothetico-deductive model is a model of diagnostic reasoning in medicine and, therefore, may be inappropriately applied to Physiotherapy, in view of the uncertainties surrounding diagnosis within the profession at present.

3 .6 Su m m a r y & Co n c l u s io n s

This chapter defined treatment planning as consisting of four stages comprising data collection, diagnosis, prescription and management of the specific dysfunction. The diagnostic phase has been the most heavily investigated in cognitive terms. There are certain attributes of diagnosis, which affect the theoretical approach to the research. It is fundamentally a problem-solving exercise, where the solution unfolds gradually over time, as more data are acquired about the specific dysfunction. The problem space is gradually contracted, until the most plausible solution from the weight of evidence is found. A decision is made based on the result of the problem solving exercise and the enterprise requires an extensive knowledge base. Because of the uncertainty in clinical problems, the data may be interpreted in different ways, thus leading to different conclusions. Ambiguities are common in the clinical context, creating difficulties for all practitioners in sifting the relevant from irrelevant cues. Adopting a traditional psychological approach could be risky, because they have rarely dealt with applied areas. Classical decision theory, for example, appears time- consuming and lacks an element of realism by prescribing a way decisions should be made, which does not accord with the way they are taken in practice.

In areas such as Cognitive Science and Medicine, there has been a considerable development in understanding problem solving applied to real-life problems. Novice-expert differences have been identified in many areas of problem solving. In Al, the expert has been seen as the source of information around which expert systems can be designed. A key issue in this area is the knowledge representation, which has also been identified as vital in medical diagnosis. Furthermore, it appears that the knowledge possessed by the expert may have undergone some sort of restructuring that improves speed and efficiency of access, when faced with a clinical problem. In the medical field, the hypothetico-deductive and pattern recognition models have been proposed. Whilst helpful in general, there are disputes about which form of reasoning is normative. It appears