Recent research indicates that toddlers and infants succeed at various non-verbal spontaneous-response false-belief tasks; here we asked whether toddlers would also succeed at verbal spontaneous-response false-belief tasks that imposed significant linguistic demands. 2.5-year-olds were tested using two novel tasks: a preferential-looking task in which children listened to a false-belief story while looking at a picture book (with matching and non-matching pictures), and a violation-of-expectation task in which children watched an adult “Subject” answer (correctly or incorrectly) a standard false-belief question. Positive results were obtained with both tasks, despite their linguistic demands. These results (1) support the distinction between spontaneous-and elicited-response tasks by showing that toddlers succeed at verbal false-belief tasks that do not require them to answer direct questions about agents’ false beliefs, (2) reinforce claims of robust continuity in early false-belief understanding as assessed by spontaneous-response tasks, and (3) provide researchers with new experimental tasks for exploring early false-belief understanding in neurotypical and autistic populations.
Much of the research on object individuation in infancy has used a task in which two different objects emerge in alternation from behind a large screen, which is then removed to reveal either one or two objects. In their seminal work, Xu and Carey (1996) found that it is typically not until the end of the first year that infants detect a violation when a single object is revealed. Since then, a large number of investigations have modified the standard task in various ways and found that young infants succeed with some but not with other modifications, yielding a complex and unwieldy picture. In this article, we argue that this confusing picture can be better understood by bringing to bear insights from a related subfield of infancy research, physical reasoning. By considering how infants reason about object information within and across physical events, we can make sense of apparently inconsistent findings from different object-individuation tasks. In turn, object-individuation findings deepen our understanding of how physical reasoning develops in infancy. Integrating the insights from physical-reasoning and object-individuation investigations thus enriches both subfields and brings about a clearer account of how infants represent objects and events.
The present research used a preferential-reaching task to examine whether 9- and 11-month-olds (n = 144) could infer the relative weights of two objects resting on a soft, compressible platform. Experiment 1 established that infants reached preferentially for the lighter of two boxes. In Experiments 2 to 4, infants saw two boxes identical except in weight resting on a cotton wool platform. Infants reached prospectively for the lighter box, but only when their initial exploratory activities provided critical information. At 11 months, infants succeeded as long as they first determined that the platform was compressible; at 9 months, infants succeeded only if they also explored the boxes and thus had advance knowledge that they differed in weight.
Prior research suggests that children younger than age 3 or 4 do not understand that an agent may be deceived by an object’s misleading appearance. The authors asked whether 14.5-month-olds would give evidence in a violation-of-expectation task that they understand that agents may form false perceptions. Infants first watched events in which an agent faced a stuffed skunk and a doll with blue pigtails; the agent consistently reached for the doll, suggesting that she preferred it over the skunk. Next, while the agent was absent, the doll was hidden in a plain box, and the skunk was hidden in a box with a tuft of blue hair protruding from under its lid. Infants expected the agent to be misled by the tuft’s resemblance to the doll’s hair and to falsely perceive it as belonging to the doll. These and other results indicate that 14.5-month-old infants can already reason about agents’ false perceptions.
infant cognition; action comprehension; psychological reasoning; theory of mind; false perception
Prior research suggests that infants attend to a variable in an event category when they have identified it as relevant for predicting outcomes in the category, and that the age at which infants identify a variable depends largely on the age at which they are exposed to appropriate observations. Thus, depending on age of exposure, infants may identify the same variable at different ages in different event categories. A good case in point is the variable height, which is identified at about 3.5 months in occlusion events, but only at about 12 months in covering events and 14 months in tube events. In the present experiments, 11-month-olds detected a change to an object’s height in an occlusion but not a covering event, and 12.5-month-olds detected a similar change in a covering but not a tube event. Thus, infants succeeded in detecting a change to an object’s height in an event where height had been identified as a relevant variable, but failed to detect the exact same change in another event where height had not yet been identified as a relevant variable. These findings provide evidence that infants’ physical knowledge affects which changes they detect in physical events. Possible mechanisms underlying these findings are also discussed, in light of recent accounts of change detection in adults.
For more than two decades, researchers have argued that young children do not understand mental states such as beliefs. Part of the evidence for this claim comes from preschoolers’ failure at verbal tasks that require the understanding that others may hold false beliefs. Here, we used a novel nonverbal task to examine 15-month-old infants’ ability to predict an actor’s behavior on the basis of her true or false belief about a toy’s hiding place. Results were positive, supporting the view that, from a young age, children appeal to mental states—goals, perceptions, and beliefs—to explain the behavior of others.
The notion of innate ideas has long been the subject of intense debate in the fields of philosophy and cognitive science. Over the past few decades, methodological advances have made it possible for developmental researchers to begin to examine what innate ideas—what innate concepts and principles—might contribute to infants’ knowledge acquisition in various core domains. This article focuses on the domain of physical reasoning and on Spelke’s (1988, 1994) proposal that principles of continuity and cohesion guide infants’ interpretation of physical events. The article reviews recent evidence that these two principles are in fact corollaries of a single and more powerful principle of persistence, which states that objects persist, as they are, in time and space.
The present research investigated whether 13.5-month-old infants would attribute to an actor a disposition to perform a recurring action, and would then use this information to predict which of two new objects—one that could be used to perform the action and one that could not—the actor would grasp next. During familiarization, the infants watched an actor slide various objects forward and backward on an apparatus floor. During test, the infants saw two new identical objects placed side by side: one stood inside a short frame that left little room for sliding; the other stood inside a longer frame that left ample room for sliding. The infants who saw the actor grasp the object inside the short frame looked reliably longer than those who saw the actor grasp the object inside the long frame. This and control results from a lifting condition provide evidence that by 13.5 months, infants can attribute to an actor a disposition to perform a particular action.
Two experiments examined infants’ expectations about how an experimenter should distribute resources and rewards to others. In Experiment 1, 19-month-olds expected an experimenter to divide two items equally, as opposed to unequally, between two individuals. Infants held no particular expectation when the individuals were replaced with inanimate objects, or when the experimenter simply removed covers in front of the individuals to reveal the items (instead of distributing them). In Experiment 2, 21-month-olds expected an experimenter to give a reward to each of two individuals when both had worked to complete an assigned chore, but not when one of the individuals had done all the work while the other played. Infants held this expectation only when the experimenter could determine through visual inspection who had worked and who had not. Together, these results provide converging evidence that infants in the second year of life already possess context sensitive-expectations relevant to fairness.
social cognition; morality; infant development
The present research examined whether 9.5-month-old infants can attribute to an agent a disposition to perform a particular action on objects, and can then use this disposition to predict which of two new objects—one that can be used to perform the action and one that cannot—the agent is likely to reach for next. The infants first received familiarization trials in which they watched an agent slide either three (Experiments 1 and 3) or six (Experiment 2) different objects forward and backward on an apparatus floor. During test, the infants saw two new identical objects placed side by side: one stood inside a short frame that left little room for sliding, and the other stood inside a longer frame that left ample room for sliding. The infants who saw the agent slide six different objects attributed to her a disposition to slide objects: they expected her to select the “slidable” as opposed to the “unslidable” test object, and they looked reliably longer when she did not. In contrast, the infants who saw the agent slide only three different objects looked about equally when she selected either test object. These results add to recent evidence that infants in the first year of life can attribute dispositions to agents, and can use these dispositions to help predict agents’ actions in new contexts.
Infant cognition; Disposition; Action comprehension; Psychological reasoning
Recent research on infants’ responses to occlusion and containment events indicates that, although some violations of the continuity principle are detected at an early age e.g. Aguiar, A., & Baillargeon, R. (1999). 2.5-month-old infants’ reasoning about when objects should and should not be occluded. Cognitive Psychology 39, 116–157; Hesposs, S. J., & Baillargeon, R. (2001). Knowledge about containment events in very young infants. Cognition 78, 207–245; Luo, Y., & Baillargeon, R. (in press). When the ordinary seems unexpected: Evidence for rule-based reasoning in young infants. Cognition; Wilcox, T., Nadel, L., & Rosser, R. (1996). Location memory in healthy preterm and full-term infants. Infant Behavior & Development 19, 309–323, others are not detected until much later e.g. Baillargeon, R., & DeVos, J. (1991). Object permanence in young infants: Further evidence. Child Development 62, 1227–1246; Hespos, S. J., & Baillargeon, R. (2001). Infants’ knowledge about occlusion and containment events: A surprising discrepancy. Psychological Science 12, 140–147; Luo, Y., & Baillargeon, R. (2004). Infants’ reasoning about events involving transparent occluders and containers. Manuscript in preparation; Wilcox, T. (1999). Object individuation: Infants’ use of shape, size, pattern, and color. Cognition 72, 125–166. The present research focused on events involving covers or tubes, and brought to light additional examples of early and late successes in infants’ ability to detect continuity violations. In Experiment 1, 2.5- to 3-month-old infants were surprised (1) when a cover was lowered over an object, slid to the right, and lifted to reveal no object; and (2) when a cover was lowered over an object, slid behind the left half of a screen, lifted above the screen, moved to the right, lowered behind the right half of the screen, slid past the screen, and finally lifted to reveal the object. In Experiments 2 and 3, 9- and 11-month-old infants were not surprised when a short cover was lowered over a tall object until it became fully hidden; only 12-month-old infants detected this violation. Finally, in Experiment 4, 9-, 12-, and 13-month-old infants were not surprised when a tall object was lowered inside a short tube until it became fully hidden; only 14-month-old infants detected this violation. A new account of infants’ physical reasoning attempts to make sense of all of these results. New research directions suggested by the account are also discussed.
Physical reasoning in infancy; Continuity violations; Event categories
Until recently, it was generally assumed that the ability to attribute false beliefs did not emerge until about 4 years of age. However, recent reports using spontaneous- as opposed to elicited-response tasks have suggested that this ability may be present much earlier. To date, researchers have employed two kinds of spontaneous-response false-belief tasks: violation-of-expectation tasks have been used with infants in the second year of life, and anticipatory-looking tasks have been used with toddlers in the third year of life. In the present research, 2.5-year-old toddlers were tested in violation-of-expectation tasks involving a change-of-location situation (Experiment 1) and an unexpected-contents situation (Experiment 2). Results were positive in both situations, providing the first demonstrations of false-belief understanding in toddlers using violation-of-expectation tasks and, as such, pointing to a consistent and continuous picture of early false-belief understanding.
Some researchers have suggested that infants’ ability to reason about goals develops as a result of their experiences with human agents and is then gradually extended to other agents. Other researchers have proposed that goal attribution is rooted in a specialized system of reasoning that is activated whenever infants encounter entities with appropriate features (e.g., self-propulsion). The first view predicts that young infants should attribute goals to human but not other agents; the second view predicts that young infants should attribute goals to both human and nonhuman agents. The present research revealed that 5-month-old infants (the youngest found thus far to attribute goals to human agents) also attribute goals to nonhuman agents. In two experiments, infants interpreted the actions of a self-propelled box as goal-directed. These results provide support for the view that from an early age, infants attribute goals to any entity they identify as an agent.
There is increasing evidence that infants’ representations of physical events can be enhanced through appropriate experiences in the laboratory. Most of this research has involved administering infants multiple training trials, often with multiple objects. In the present research, 8-month-olds were induced to detect a physical violation in a single trial. The experiments built on previous evidence that for occlusion events, infants encode height information at about age 3.5 months, but for covering events, they encode height information only at about age 12 months. In two experiments, a short cover was first placed in front of a short or a tall object (occlusion event); next, the cover was lowered over the tall object until it became fully hidden (covering event). Exposure to the occlusion event (but not other events in which height information was not encoded) enabled the infants to detect the violation in the covering event, much earlier than they would have otherwise.
According to a recent account of infants’ acquisition of their physical knowledge, the incremental-knowledge account, infants form distinct event categories, such as occlusion, containment, support, and collision events. In each category, infants identify one or more vectors which correspond to distinct problems that must be solved. For each vector, infants acquire a sequence of variables that enables them to predict outcomes within the vector more and more accurately over time. This account predicts that infants who have acquired only a few of the variables in a sequence should err in two ways in violation-of-expectation tasks: (1) they should view impossible events consistent with their incomplete knowledge as expected (errors of omission), and (2) they should view possible events inconsistent with their incomplete knowledge as unexpected (errors of commission). Many reports have shown that infants who have not yet identified a variable in an event category produce errors of omission: they fail to view impossible events involving the variable as unexpected. However, there has been no report revealing errors of commission in infants’ responses to possible events. The present research examined whether 3- and 2.5-month-old infants, whose knowledge of occlusion events is very limited, would produce errors of commission as well as errors of omission when responding to these events. At 3 months of age, infants viewed as unexpected a possible event in which a tall cylinder became visible when passing behind a tall screen with a very large opening extending from its upper edge. At 2.5 months, infants viewed as unexpected a possible event in which a tall cylinder became visible when passing behind a tall screen with a very large opening extending from its lower edge. These findings provide a new kind of evidence for the incremental-knowledge account, and more generally for the notion that infants, like older children and adults, engage in rule-based reasoning about physical events.
Rule-based reasoning in infancy; Occlusion events; Errors of omission and commission
Recent research suggests that infants and toddlers succeed at a wide range of nonelicited-response false-belief tasks (i.e., tasks that do not require children to answer a direct question about a mistaken agent’s likely behavior). However, one exception to this generalization comes from verbal anticipatory-looking tasks, which have produced inconsistent findings with toddlers. One possible explanation for these findings is that toddlers succeed when they correctly interpret the prompt as a self-addressed utterance (making the task a nonelicited-response task), but fail when they mistakenly interpret the prompt as a direct question (making the task an elicited-response task). Here, 2.5-year-old toddlers were tested in a verbal anticipatory-looking task that was designed to help them interpret the anticipatory prompt as a self-addressed utterance: the experimenter looked at the ceiling, chin in hand, during and after the prompt. Children gave evidence of false-belief understanding in this task, but failed when the experimenter looked at the child during and after the prompt. These results reinforce claims of robust continuity in early false-belief reasoning and provide additional support for the distinction between nonelicited- and elicited-response false-belief tasks. Three accounts of the discrepant results obtained with these tasks—and of early false-belief understanding more generally—are discussed.
anticipatory-looking task; false-belief understanding; theory of mind; toddlers
Can infants detect that an object has magically disappeared, broken apart or changed color while briefly hidden? Recent research suggests that infants detect some but not other ‘impossible’ changes; and that various contextual manipulations can induce infants to detect changes they would not otherwise detect. We present an account that includes three systems: a physical-reasoning, an object-tracking, and an object-representation system. What impossible changes infants detect depends on what object information is included in the physical-reasoning system; this information becomes subject to a principle of persistence, which states that objects can undergo no spontaneous or uncaused change. What contextual manipulations induce infants to detect impossible changes depends on complex interplays between the physical-reasoning system and the object-tracking and object-representation systems.
Are 15-month-old infants able to detect a violation in the consistency of an event sequence that involves pretense? In Experiment 1, infants detected a violation when an actor pretended to pour liquid into one cup and then pretended to drink from another cup. In Experiment 2, infants no longer detected a violation when the cups were replaced with objects not typically used in the context of drinking actions, either shoes or tubes. Experiment 3 showed that infants’ difficulty in Experiment 2 was not due to the use of atypical objects per se, but arose from the novelty of seeing an actor appearing to drink from these objects. After receiving a single familiarization trial in which they observed the actor pretend to drink from either a shoe or a tube, infants now detected a violation when the actor pretended to pour into and to drink from different shoes or tubes. Thus, at an age (or just before the age) when infants are beginning to engage in pretend play, they are able to show comprehension of at least one aspect of pretense in a violation-of-expectation task: specifically, they are able to detect violations in the consistency of pretend action sequences.
Cognitive development; Infancy; Pretense comprehension; Theory of mind
As they observe or produce events, infants identify variables that help them predict outcomes in each category of events. How do infants identify a new variable? An explanation-based learning (EBL) account suggests three essential steps: (1) observing contrastive outcomes relevant to the variable; (2) discovering the conditions associated with these outcomes; and (3) generating an explanation for the condition-outcome regularity discovered. In Experiments 1–3, 9-month-old infants watched events designed to “teach” them the variable height in covering events. After watching these events, designed in accord with the EBL account, the infants detected a height violation in a covering event, three months earlier than they ordinarily would have. In Experiments 4–6, the “teaching” events were modified to remove one of the EBL steps, and the infants no longer detected the height violation. The present findings thus support the EBL account and help specify the processes by which infants acquire their physical knowledge.
Infant cognition; knowledge acquisition; physical reasoning; identification of variables; explanation-based learning; event categories
Reports that infants in the second year of life can attribute false beliefs to others have all used a search paradigm in which an agent with a false belief about an object’s location searches for the object. The present research asked whether 18-month-olds would still demonstrate false-belief understanding when tested with a novel non-search paradigm. An experimenter shook an object, demonstrating that it rattled, and then asked an agent, “Can you do it?” In response to this prompt, the agent selected one of two test objects. Infants realized that the agent could be led through inference (Experiment 1) or memory (Experiment 2) to hold a false belief about which of the two test objects rattled. These results suggest that 18-month-olds can attribute false beliefs about non-obvious properties to others, and can do so in a non-search paradigm. These and additional results (Experiment 3) help address several alternative interpretations of false-belief findings with infants.
Recent investigations of early psychological understanding have revealed three key findings. First, young infants attribute goals and dispositions to any entity they perceive as an agent, whether human or non-human. Second, when interpreting an agent’s actions in a scene, young infants take into account the agent’s representation of the scene, even if this representation is less complete than their own. Third, at least by the second year of life, infants recognize that agents can hold false beliefs about a scene. Together, these findings support a system-based, mentalistic account of early psychological reasoning.
infant cognition; psychological understanding; mentalistic reasoning
At what age can children attribute false beliefs to others? Traditionally, investigations into this question have used elicited-response tasks in which children are asked a direct question about an agent's' false belief. Results from these tasks indicate that the ability to attribute false beliefs does not emerge until about age 4. However, recent investigations using spontaneous-response tasks suggest that this ability is present much earlier. Here we review results from various spontaneous-response tasks which suggest that infants in the second year of life can already attribute false beliefs about location and identity as well as false perceptions. We also consider alternative interpretations that have been offered for these results, and discuss why elicited-response tasks are particularly difficult for young children.
Recent research has shown that infants as young as 13 months can attribute false beliefs to agents, suggesting that the psychological-reasoning subsystem necessary for attributing reality-incongruent informational states (SS2) is operational in infancy. The present research asked whether 18-month-olds’ false-belief reasoning extends to false beliefs about object identity. Infants watched events involving an agent and two toy penguins; one penguin could be disassembled (2-piece penguin) and the other could not (1-piece penguin). Infants realized that outdated contextual information could lead the agent to falsely believe she was facing the 1-piece rather than the 2-piece penguin, suggesting that 18-month-olds can attribute false beliefs about the identity of objects and providing new evidence for SS2 reasoning in the second year of life.
The present research examined whether 5- to 6.5-month-old infants would hold different expectations about various physical events involving a box after receiving evidence that it was either inert or self-propelled. Infants were surprised if the inert but not the self-propelled box: reversed direction spontaneously (Experiment 1); remained stationary when hit or pulled (Experiments 3 and 3A); remained stable when released in midair or with inadequate support from a platform (Experiment 4); or disappeared when briefly hidden by one of two adjacent screens (the second screen provided the self-propelled box with an alternative hiding place; Experiment 5). On the other hand, infants were surprised if the inert or the self-propelled box appeared to pass through an obstacle (Experiment 2) or disappeared when briefly hidden by a single screen (Experiment 5). The present results indicate that infants as young as 5 months of age distinguish between inert and self-propelled objects and hold different expectations for physical events involving these objects, even when incidental differences between the objects are controlled. These findings are consistent with the proposal by Gelman (1990), Leslie (1994), and others that infants endow self-propelled objects with an internal source of energy. Possible links between infants’ concepts of self-propelled object, agent, and animal are also discussed.
Do 18-month-olds understand that an agent’s false belief can be corrected by an appropriate, though not an inappropriate, communication? In Experiment 1, infants watched a series of events involving two agents, a ball, and two containers: a box and a cup. To start, agent1 played with the ball and then hid it in the box, while agent2 looked on. Next, in agent1’s absence, agent2 moved the ball from the box to the cup. When agent1 returned, agent2 told her “The ball is in the cup!” (informative-intervention condition) or “I like the cup!” (uninformative-intervention condition). During test, agent1 reached for either the box (box event) or the cup (cup event). In the informative-intervention condition, infants who saw the box event looked reliably longer than those who saw the cup event; in the uninformative-intervention condition, the reverse pattern was found. These results suggest that infants expected agent1’s false belief about the ball’s location to be corrected when she was told “The ball is in the cup!”, but not “I like the cup!”. In Experiment 2, agent2 simply pointed to the ball’s new location, and infants again expected agent1’s false belief to be corrected. These and control results provide additional evidence that infants in the second year of life can attribute false beliefs to agents. In addition, the results suggest that by 18 months of age infants expect agents’ false beliefs to be corrected by relevant communications involving words or gestures.