An fMRI analysis of the efficacy of Euler diagrams in logical reasoning

We compared participant performance and brain activation changes during a syllogism-solving task with and without Euler diagrams, using functional magnetic resonance imaging (fMRI). Our experiment showed that when Euler diagrams were present, (i) response times in the task were significantly shorter than those in the usual reasoning task comprising only sentences, and (ii) the magnitude of activation in the left middle frontal gyrus (near BA 10), left inferior PFC (near BA 47), and left dorsal PFC (BA 6) was reduced. Result (i) provides evidence for the occurrence of cognitive offloading even when participants handle information of both sentences and diagrams in reasoning tasks. Result (ii) suggests that complex processes of inferences can be replaced by simple diagram manipulation. It is argued that cognitive details that are not fully specified by behavioral studies can be made salient using neuroscientific methods.