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Decision Making: Dual Process Theory
Over the past two decades, dual process theory (DPT) has been recognized as a reliable model of the decision-making process in the psychology literature.9 DPT proposes two unique processes of thinking during decision making, referred to as System 1 and System 2, or Type 1 and Type 2, processes. A brief introduction to DPT is given here for practicing clinicians, but a detailed discussion of the literature pertaining to this concept is beyond the scope of this review.
System 1 processes are “intuitive,” utilize pattern recognition and heuristics, and rely heavily on the context or conditions in which the decision is made. The intuitive System 1 mode of thinking uses a pattern recognition or “gut reaction” approach.10 It is fast and reflexive but can be subject to deficits in predictive power and reliability.10 Experienced clinicians use pattern recognition in conditions presenting with classic signs and symptoms.10 For example, the clinician who evaluates a 12-year-old child with an annular, erythemic patch with central clearing on the forearm and immediately diagnoses ringworm is thinking in the intuitive mode. Generally, human beings are most comfortable in this decision mode because it involves intuition and requires less mental effort and concentration. For clinicians, System 1 thinking is the default defense mechanism against “decision fatigue” and “cognitive overload” during a busy shift, and it is the thinking mode used when clinicians are stressed, hurried, tired, and working with a lack of resources.9,10 Croskerry maintains, however, that such clinical situations, and the reliance on System 1 thinking that such situations entail, can make clinicians more vulnerable to certain biases.9
System 2 thinking is analytic, deductive, slow, and deliberate. This mode of thinking has high predictive power with high reliability, and it is less influenced by the context or conditions in which the decision is being made.10 Clinicians use this mode of thinking when patients present with vague signs and symptoms and a diagnosis is not instantly recognized.10 System 2 decision making would be required, for example, when evaluating a 55-year-old woman with chest pain. The clinical condition requires the clinician to acquire more data and make a conscious effort to analyze results, and arriving at a clinical decision in this situation takes more time. Shortcuts due to time pressures can have devastating outcomes in this setting. It should be mentioned, however, that psychology research has shown that the System 2 analytic approach is mentally taxing and may also result in poor decisions (“thinking too much”).11
Intuitive and analytic thinking are not independent of each other. During a clinical encounter, there is unconscious switching back and forth between the two modes as the clinician evaluates the information at hand in order to produce a decision.12 A patient presenting with a chief complaint may trigger a System 1 decision, but due to uncertainty there may be a “System 2 override”where the clinician consciously forces herself to reassess and perform further analysis.10 System 1 intuitive decision processes become more dominant with experience. Many encounters requiring System 2 thinking early in a clinician’s career may become System 1 decisions as the clinician gains expertise.10 This results as the clinician develops a “mental library” of previous encounters with commonly seen medical conditions.13 It is important to note that clinical decision errors often result from a combination of knowledge gaps and processing malfunctions and not from one process alone.14
Similarly, diagnostic errors are not purely a result of cognitive biases or reliance on System 1 or System 2 thinking, but rather are a result of multiple factors.In a study that looked at provider time to diagnosis and accuracy of diagnosis, results indicated that System 1 reasoning was not more error prone than System 2 thinking.15 Experienced clinicians emphasize that errors can occur at any time or in any context in both System 1 and 2 modes of thinking.16
The vast majority of human decisions—95%—are made in System 1 mode, while only 5% of our “thinking” is conscious analytic thought.17 Croskerry suggests that clinical reasoning defaults to the faster, more mentally economic System 1 thinking, which can make clinicians prone to error by allowing intuition, heuristics, and processes that are most vulnerable to mistakes—stereotyping, prejudices, and biases—to influence a decision.9,18 Both novice and expert clinicians should be encouraged to develop insight into their intuitive and analytic decision-making processes and become aware of which thinking mode they are using in a specific clinical situation.
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