Counterfactuals in action: an fMRI study of counterfactual sentences describing physical effort.

Counterfactual statements such as if Mary had cleaned the room, she would have moved the sofa convey both actual and hypothetical actions, namely, that Mary did not clean the room or move the sofa, but she would have done so in some possible past situation. Such statements are ubiquitous in daily life and are involved in critical cognitive activities like decision-making and evaluation of alternative outcomes. Here, we investigate the brain mechanisms and the nature of the semantic representations involved in understanding the complex meaning of counterfactual statements. We used fMRI to examine brain responses to counterfactual statements describing actions of high and low physical effort and compared them to similar factual statements describing the same actions. Results indicated that the inferior parietal lobule, known to support planning of object-directed actions, responded more strongly to high-effort than low-effort statements. Moreover, counterfactual statements, compared to factual ones, recruited a distinctive neural network partially overlapping with action execution networks. This network included medial pre-motor and pre-frontal structures, which underpin selection and inhibition of alternative action representations, and parahippocampal and temporal regions, involved in retrieving episodic memories. We argue that counterfactual comprehension recruit action-related networks encoding and managing alternative representations of behaviors.