Abstract
Individuals scoring high in fluid intelligence tasks generally perform very efficiently in problem solving tasks and analogical reasoning tasks presumably because they are able to select the task-relevant information very quickly and focus on a limited set of task-relevant cognitive operations. Moreover, individuals with high fluid intelligence produce more representational hand and arm gestures when describing a geometric analogy task than individuals with average fluid intelligence. No study has yet addressed the relationship between intelligence, gesture production, and brain structure, to our knowledge. That was the purpose of our study. To characterize the relation between intelligence, gesture production, and brain structure we assessed the frequency of representational gestures and cortical thickness values in a group of adolescents differing in fluid intelligence. Individuals scoring high in fluid intelligence showed higher accuracy in the geometric analogy task and produced more representational gestures (in particular more movement gestures) when explaining how they solved the task and showed larger cortical thickness values in some regions in the left hemisphere (namely the pars opercularis, superior frontal, and temporal cortex) than individuals with average fluid intelligence. Moreover, the left pars opercularis (a part of Broca's area) and left transverse temporal cortex showed larger cortical thickness values in participants who produced representational and in particular movement gestures compared to those who did not. Our results thus indicate that cortical thickness of those brain regions is related to both high fluid intelligence and the production of gestures. Results are discussed in the gestures-as-simulated-action framework that states that gestures result from simulated perception and simulated action that underlie embodied language and mental imagery.