In human-robot interactions, people tend to attribute them mental states such as intentionality to make sense of their behaviour:the intentional stance. These inferences deeply influence how one will consider, engage and behave towards robots. However,people highly differ in their likelihood to adopt this intentional stance. Therefore it seems crucial to assess these interindividualdifferences to better evaluate and understand human-robot interactions. In two studies we developed and validated the structureof a task aiming at evaluating to what extent people adopt the intentional stance toward robots. The method consists in a taskthat probes participants’ stance by requiring them to choose the likelihood of an explanation (mentalistic vs. mechanistic) ofbehaviour of a robot depicted in a naturalistic scenario. Results showed a reliable psychometric structure of the present task toevaluate the mentalistic bias of participants as a proxy of the intentional stance. We further discuss the importance of consideringthese interindividual differences in human-robot interactions studies and social robotics