Empirical Evaluation of Possibility Theory in Human Radiological Diagnosis

An experiment was conducted in order to evaluate what normative framework is pertinent for dealing with confidence judgements in human experts. 24 films were shown to 4 experimented radiologists. A specific apparatus was designed in order to obtain diagnoses and the associated confidence judgements. With regard to methodology, results showed that confidence judgements under the form of a subjective probability were equal to confidence judgements provided under the form of possibilistic measures. At behavioural level, results showed that possibilistic confidence judgements were related to exploration time and to the order of diagnosis expression. At formal level, conjunctions provided by radiologists fitted a possibilistic model (Min-decomposability) but there was a significant difference with the probabilistic model (multiplication). Data related to disjunction (OR and XOR) of certainty judgements did not allow differentiating both models. However, subjects also seemed to apply a Min rule for conjunction of possibilities and a Max rule for disjunction of certainties.