Evidence supporting dual-process theory of medical diagnosis: a functional near-infrared spectroscopy study

The objective of this study was to determine the extent to which the dual-process theory of medical diagnosis enjoys neuroscientific support. To that end, the study explored whether neurological correlates of system-2 thinking could be located in the brain. It was hypothesised that system-2 thinking could be observed as the activation of the prefrontal cortex.

An experimental paradigm was applied that consisted of a learning and a test phase. During the learning phase, 22 medical students were trained in diagnosing chest X-rays. Four of these eight cases were presented repeatedly, to develop a high level of expertise for these cases. During the test phase, all eight cases were presented and the participants' prefrontal cortex was scanned using functional near-infrared spectroscopy. Response time and diagnostic accuracy were recorded as behavioural indicators.

The results revealed that participants' diagnostic accuracy in the test phase was significantly higher for the trained cases as compared with the untrained cases (F[1, 21] = 138.80, p < 0.001, η²  = 0.87). Also, their response time was significantly shorter for these cases (F[1, 21] = 18.12, p < 0.001, η²  = 0.46). Finally, the results revealed that only for the untrained cases, could a significant activation of the anterolateral prefrontal cortex be observed (F[1, 21] = 21.00, p < 0.01, η²  = 0.34).

The fact that only untrained cases triggered higher levels of blood oxygenation in the prefrontal cortex is an indication that system-2 thinking is a cognitive process distinct from system 1. Implications of these findings for the validity of the dual-process theory are discussed.