In Experiment 1, 15-month-old infants readily detected a violation in a highly familiar event sequence when common objects were used, looking longer when an actor pretended to pour into one cup and then inconsistently pretended to drink from another cup, than when she pretended to pour into and to drink from the same cup. This finding suggests that at an age before infants are commonly engaging in pretend play, they have some expectations about how others should engage in pretense. In Experiment 2, infants failed to detect violations in the same event sequences when substitute objects were used, suggesting that perhaps infants did not understand the pretend sequences of Experiment 1, but merely had specific scripted expectations tied to sequences of actions involving jugs and cups. However, in Experiment 3, infants detected violations in the test events from Experiment 2 after they had been familiarized with the actor performing pretend drinking actions on a similar object. This pattern of results demonstrated that the infants were able to detect the violation in the sequences involving the substitute objects, but needed a little more time or exposure to do so.
The particular pretend sequences we used were closely comparable to those in the ‘simple’ pretend tasks of Bosco et al. (2006)
that required infants to produce a play action or to point in response to a question. In that study, 16-month-olds also passed pretend pouring-and-drinking scenarios. The present results are consistent with these previous results but extend them to younger infants using a looking-time measure. The present results indicate that violation-of-expectation tasks can be a useful addition to traditional measures of pretend-play ability. Traditional measures require the child to enter into and share pretense with another person, often the experimenter, by producing a playful response or by answering a question, or to produce play actions in solitary pretense. Such measures require the child to produce a voluntary response or produce play; they often require some language ability at the same time. Looking-time measures do not require infants to produce a play action and are usually entirely non-verbal. Such measures may be especially useful with special populations such as children with autism or with language delays. Bosco et al. found that 16-month-olds failed on more complex pretense, such as a task in which an imaginary filling-emptying-bowls sequence was followed by a pretend feeding of a hungry dog from either of two bowls, only one of which should contain imaginary food. With normally developing infants, it will be interesting to see if infants of this age can pass such a scenario in a violation-of-expectation task.
By 15 months, infants can follow a pretend sequence. They expect a pretend pouring event to be followed by a pretend drinking event from the same cup, shoe, or tube. Experiment 2 ruled out perceptual highlighting as an explanation for these results. Experiment 3 ruled out simple knowledge of scripts, because infants are unlikely to have a script for pouring or drinking with shoes or tubes, let alone a script for pouring into and drinking from the same shoe or tube. The infants were able to reason about pretend sequences involving these substitute objects, but found them harder. However, a single trial to acquaint, or perhaps to prime, the infants with the idea of pretend drinking from a shoe or tube was all that was required in order to establish a subsequent expectation that the actor should ‘drink’ from the same shoe or tube that she had ‘poured something into’ earlier. Our results therefore extend the existing literature on goal detection in infancy. Previous findings have shown that by the second year of life, infants detect a wide range of agents’ intentions in action or goals (e.g., Elsner, 2007
; Gergely et al., 2002
; Song & Baillargeon, 2007
; see also Bíró & Leslie, in press
, for a recent review). The present findings indicate that by 15 months of age, infants can also form expectations regarding actors’ intentions towards objects or properties that do not actually exist.
Might the present results be explained simply by saying that, as Woodward (1998)
showed, even young infants expect an actor who intentionally interacts with one of two objects to later act again on this rather than the other object? The difference in the present case, of course, is that the actor did not actually interact with or act upon either of the objects during the test event. During the pre-trials, the actor acted only upon the jug, merely holding it above one or the other of the objects without further consequence. Infants in the Woodward paradigm require there to be a known cause-effect relation between the act and the target object; without a known effect, infants will not interpret the act as directed toward that object (Bíró & Leslie, in press
; Király et al., 2003
; Woodward, 1999
). In our pretend sequences the actor’s actions had no effects on the test object; at least, no actual
effects. However, the results do suggest that the infants interpreted these actions as if
they did have effects; this, we suggest, is because they interpreted the sequences as pretend scenarios. Future research should examine more closely the specificity of the infants’ interpretations of pretense: for example, are their expectations as specific in looking-time studies as they were with the production measures used by Bosco et al. (2006)
The ability to interpret agents’ behavior in relation to intentional states that have a counterfactual or imaginary content has been held to be a hallmark of mentalistic understanding (e.g., Leslie, 1987
). In this regard, the present results comport with recent findings by Onishi and Baillargeon (2005)
that 15-month-olds expect an actor to behave according to the actor’s belief about the state of the world, even when the actor’s belief is false. Perner and Ruffman (2005)
; also Ruffman and Perner, 2005
suggested that the results of Onishi and Baillargeon sprang from a simple innate rule infants may have, rather than from any mentalistic notion. The proposed rule, that an actor should behave toward an object in the last location in which the actor saw the object, will not account for the present results. The ‘object’ toward which our actor acted was imaginary and was therefore never seen.
As adults, when we slip into a world of pretense or fiction, though we expect to encounter novel events and imaginary objects and people, we also expect an entire episode to have internal consistency. For example, if we read about the regicidal Macbeth ascending the Scottish throne in one scene, we do not expect Macbeth to be working in a bank in California in the next. Likewise, if Amanda pretends to be ill so as not to go to school, she should not be found running around outside playing basketball. In the present research, we demonstrated that 15-month-old infants have at least an elementary understanding that even pretend event sequences should be internally consistent.
Such expectations of consistency do not necessarily require sophisticated understanding but may simply follow from the basic processing mechanisms of pretense. For example, according to the model presented by Leslie (1987
), pretense begins by stipulating a state of affairs, for example, ‘there is water in this jug’. This stipulated state of affairs is only imaginary (because the jug is empty), but developing this stipulation into a sequence or game can proceed by mentally applying real-world knowledge. For example, in the real world, if you turn a jug of water upside down, then the water will come out and pour in a downward direction. In a reasoning process, real-world knowledge as in the previous if-then rule can be applied to the stipulated (pretend) situation ‘there is water in this jug’. Thus, as long as the inferred consequent is also marked as a pretend situation ‘the water pours into the cup’, no confusion or representational abuse will arise.
Of course, it is possible to pretend, for example, that water poured out of a jug goes in an upward direction. But because this outcome departs from real-world knowledge, it will have to be stipulated rather than inferred. The upshot is that unless some imaginary situation is either stipulated or inferred from something that has been stipulated, the pretense will retain real-world assumptions. Put another way, real-world assumptions are maintained unless otherwise specified. This mode of operation is just economy of effort, a kind of ‘representational inertia’: the pretend world will be represented as minimally different from the (assumed) real world. One interpretation, then, of our finding that 15-month-olds expect pretend event sequences to be internally consistent is simply that this is the most economical representation to compute—the representation with the greatest ‘inertia’. However, it constitutes an extension of the primary physical reasoning that is the achievement of infants in the first year. It is the birth of counterfactual reasoning.
Finally, according to some accounts, the social aspects of interactions are of central importance for learning about intentionality (Rochat, 2007
) and about pretend play (Les-lie, 1987
). In the real world, pretend play is very often shared between partners as a type of intentional communication (Leslie & Happé, 1989
). It is possible to think of the present experiments in this light where the infant spontaneously assumes the actor is trying to communicate with her about a pretense in which she then shares. Such speculations could be addressed in future research.
The research reported here will need to be extended to many other kinds of pretend scenarios. Until then, our findings and conclusions must remain somewhat tentative. However, the extension of the violation-of-expectation method to the study of pretense and other issues long central to ‘theory of mind’ development (e.g., Onishi & Baillargeon, 2005
) holds out great promise of opening up new routes to understanding the structure of infant social intelligence.