Can 12 large clowns fit in a Mini Cooper? Or when are beliefs and reasoning explicit and conscious?

In their commentaries, Hood, Bremner and Mareschal raise several important and difficult questions about what can and cannot be attributed to infants based on their responses in violation-of-expectation (VOE) tasks. I address a few of these questions below. 1. Can we attribute to infants who detect a violation in a VOE task explicit knowledge of the physical beliefs involved in the task? Consider the 12-month-olds who respond with increased attention when a tall object becomes fully hidden under a short cover (Wang, Baillargeon & Paterson, in press). Can we say that these infants possess an explicit belief that ‘objects continue to exist when hidden’, or that ‘two objects cannot occupy the same space at the same time’, or that ‘tall objects cannot become fully hidden under short covers’? Surely not. It seems very unlikely that infants possess explicit beliefs about anything. What they do possess is an abstract computational system, a physical-reasoning system, which monitors physical events and flags those that do not unfold as expected for further scrutiny – hence the increased attention. The system is skeletal at first but rapidly improves as relevant variables are identified. However, it is highly doubtful that the knowledge used by the physical-reasoning system to monitor events is either explicit or conscious. Hood, Bremner and Mareschal may ask why, if I believe that infants do not possess explicit or conscious knowledge about objects and events, I use terms such as ‘reason’ and ‘infer’ to describe the cognitive processes that underlie infants’ responses in VOE tasks. The answer is simple: it is not possible to do otherwise. The 7.5-month-old infants who are surprised when a tall object becomes fully hidden inside a short container must reason, in some manner and at some level, that the object is too tall to become fully hidden inside the short container (Hespos & Baillargeon, 2001). Similarly, consider the 3.5-month-old infants who are surprised when a toy mouse fails to appear in a screen’s low window (1) if the screen is lowered at the start of the trial to reveal only one mouse, but not (2) if the screen remains upright throughout the trial or (3) if the screen is lowered at the start of the trial to reveal one mouse and one small screen that is large enough to hide a second mouse (Aguiar & Baillargeon, 2002). We cannot make sense of these results without attributing to infants inferential processes that enable them to posit the existence of a second mouse in (2) and (3) but not (1). Infants could not respond as they do in VOE tasks without engaging in the appropriate reasoning and inferential processes; but it does not follow that these processes must be explicit or conscious, any more than their physical beliefs are. To make these points clearer, consider an event in which 12 large clowns emerge one by one from a Mini Cooper. We would expect adults to readily detect the violation in this event; we would not expect them to be explicitly conscious, as they detected the violation, of the physical beliefs and reasoning processes that made it possible for them to do so. In this respect, adults and infants may not be fundamentally different. Of course, adults could, when pressed, describe at least some of the physical beliefs and reasoning processes that enabled them to detect the violation whereas infants could not; I return to this point below.