Dual-Process Theory
Definition
The common shorthand is System 1 and System 2, terms popularised by Kahneman.
Type 1 processing is described as fast, autonomous, high capacity and independent of working memory. Type 2 processing is slow, effortful, and depends on working memory and cognitive decoupling.
Evans and Stanovich argue the defining feature is working memory involvement and decoupling, not speed or consciousness. The various other properties often listed — associative versus rule-based, evolutionarily old versus new, unconscious versus conscious — do not reliably co-occur, and treating them as a package is where most of the trouble starts.
History
Two-process distinctions appear throughout the history of psychology. The modern form comes from reasoning research in the 1970s and 1980s and from the heuristics-and-biases programme of Tversky and Kahneman.
Thinking, Fast and Slow (2011) took the framework to a general audience and, in doing so, fixed the least defensible version of it in public understanding.
Theory
The framework's utility is that it explains why people give systematically wrong answers to problems they can solve when prompted to reflect.
The default-interventionist version holds that Type 1 generates a default response and Type 2 sometimes intervenes to override it. Parallel-competitive versions hold both operate simultaneously.
More recent work challenges the assumption that logic requires deliberation: logical intuitions appear to be available fast, and people often show sensitivity to conflict between intuition and logic before any deliberation occurs. This weakens the simple story in which intuition is the source of error and deliberation the source of correction.
Research
The Cognitive Reflection Test is the standard instrument and predicts a range of judgement outcomes, though it is now heavily contaminated by prior exposure.
Several prominent findings in this literature have not survived scrutiny. Ego depletion — that Type 2 processing draws on a limited resource that fatigue exhausts — is a major casualty, with a large preregistered multi-lab replication finding effects near zero. Several priming results associated with the framework have failed similarly.
The core reasoning findings, such as belief bias and conflict detection, have held up better than the motivational and depletion extensions.
Applications
Behavioural public policy, health communication, financial decision design, and clinical reasoning and diagnostic error.
The application to medical error — that intuitive diagnosis produces bias and deliberation corrects it — is widely taught, but interventions built on it have produced disappointing results.
Criticism
- The two systems are not systems. Treating them as unified entities is not supported, and Evans and Stanovich themselves argue against it.
- The attribute clusters do not cohere. Fast does not imply unconscious, which does not imply associative.
- It is easy to apply after the fact. Any error can be labelled System 1 and any correction System 2, which explains nothing.
- Replication problems in the associated literature are serious, particularly around depletion and priming.
- The popular version is worse than the academic one, and the popular version is what most applied work uses.
References
- Evans, J. St. B. T., & Stanovich, K. E. (2013). Dual-process theories of higher cognition: Advancing the debate. Perspectives on Psychological Science, 8(3), 223-241.
- Kahneman, D. (2011). Thinking, Fast and Slow. Farrar, Straus and Giroux.
- De Neys, W. (2012). Bias and conflict: A case for logical intuitions. Perspectives on Psychological Science, 7(1), 28-38.
- Hagger, M. S., et al. (2016). A multilab preregistered replication of the ego-depletion effect. Perspectives on Psychological Science, 11(4), 546-573.