In his presentation, “Extensional theories of behavior,” Bart Geurts, Professor of Philosophy, University of Nijmegen, The Netherlands, posed the question whether it was legitimate to say that young infant’s attribute mental states such as “beliefs” and “goals”. He highlighted the importance of building a kitbag of new terms to describe more precisely and more cautiously what infants do when they act in accordance with people’s mental states. Bart Geurts suggested that any concept defined in terms of non-actual states of affairs (such as beliefs that can differ from reality when they are false) is likely to be more complex to process than concepts that appeal only to actual states of affairs. On this basis, he advocated for avoiding the use of mental terms as much as possible when speaking about infants’ attributions.
To establish the feasibility of this project, Bart Geurts analyzed one version of the well-known “false belief task” (Onishi & Baillargeon, 2005), usually taken as a test for the capacity to attribute beliefs. In this task, an actor leaves a toy watermelon in a yellow box. While the character is away, the toy moves to a green box. In this paradigm, infants look longer at the actor when she reaches for the toy in its actual location (the green box), than when she reaches for the toy where she should expect it to be (the yellow box). The traditional interpretation of this kind of task is that children expect the actor to act on the basis of her false belief. Bart Geurts suggested that children can pass this task on the basis of purely behavioral descriptions, hence without attributing mental states such as “beliefs”. For Geurts, children may expect the actor to “get” the toy where she “locates” it. Bart Geurts concluded his presentation by offering some speculations on how children may shift from purely behavioral attributions to genuine mental state attributions.