Infants can use temporary or scant categorical information to individuate objects.

In a standard individuation task, infants see two different objects emerge in alternation from behind a screen. If they can assign distinct categorical descriptors to the two objects, they expect to see both objects when the screen is lowered; if not, they have no expectation at all about what they will see (i.e., two objects, one object, or no object). Why is contrastive categorical information critical for success at this task? According to the kind account, infants must decide whether they are facing a single object with changing properties or two different objects with stable properties, and access to permanent, intrinsic, kind information for each object resolves this difficulty. According to the two-system account, however, contrastive categorical descriptors simply provide the object-file system with unique tags for individuating the two objects and for communicating about them with the physical-reasoning system. The two-system account thus predicts that any type of contrastive categorical information, however temporary or scant it may be, should induce success at the task. Two experiments examined this prediction. Experiment 1 tested 14-month-olds (N = 96) in a standard task using two objects that differed only in their featural properties. Infants succeeded at the task when the object-file system had access to contrastive temporary categorical descriptors derived from the objects' distinct causal roles in preceding support events (e.g., formerly a support, formerly a supportee). Experiment 2 tested 9-month-olds (N = 96) in a standard task using two objects infants this age typically encode as merely featurally distinct. Infants succeeded when the object-file system had access to scant categorical descriptors derived from the objects' prior inclusion in static arrays of similarly shaped objects (e.g., block-shaped objects, cylinder-shaped objects). These and control results support the two-system account's claim that in a standard task, contrastive categorical descriptors serve to provide the object-file system with unique tags for the two objects.

The violation-of-expectation paradigm: A conceptual overview.

For over 35 years, the violation-of-expectation paradigm has been used to study the development of expectations in the first 3 years of life. A wide range of expectations has been examined, including physical, psychological, sociomoral, biological, numerical, statistical, probabilistic, and linguistic expectations. Surprisingly, despite the paradigm's widespread use and the many seminal findings it has contributed to psychological science, so far no one has tried to provide a detailed and in-depth conceptual overview of the paradigm. Here, we attempted to do just that. We first focus on the rationale of the paradigm and discuss how it has evolved over time. We then show how improved descriptions of infants' looking behavior, together with the addition of a rich panoply of brain and behavioral measures, have helped deepen our understanding of infants' responses to violations. Next, we review the paradigm's strengths and limitations. Finally, we end with a discussion of challenges that have been leveled against the paradigm over the years. Through it all, our goal was twofold. First, we sought to provide psychologists and other scientists interested in the paradigm with an informed and constructive analysis of its theoretical origins and development. Second, we wanted to take stock of what the paradigm has revealed to date about how infants reason about events, and about how surprise at unexpected events, in or out of the laboratory, can lead to learning, by prompting infants to revise their working model of the world. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

When Are Similar Individuals a Group? Early Reasoning About Similarity and In-Group Support.

Beginning in infancy, children expect individuals in a group to care for and be loyal to in-group members. One prominent cue that children use to infer that individuals belong to the same group is similarity. Does any salient similarity among individuals elicit an expectation of in-group preference, or does contextual information modulate these expectations? In Experiments 1 and 2, 12-month-old infants expected in-group preference between two individuals who wore the same novel outfit, but they dismissed this similarity if one of the outfits was used to fulfill an instrumental purpose. In Experiment 3, 26-month-old toddlers expected in-group preference between two individuals who uttered the same novel labels, but they dismissed this similarity if the labels were used to convey incidental as opposed to categorical information about the individuals. Together, the results of these experiments (N = 96) provide converging evidence that from early in life, children possess a context-sensitive mechanism for determining whether similarities mark groups.

Can 5-month-old infants consider the perspective of a novel eyeless agent? New evidence for early mentalistic reasoning.

Is early reasoning about an agent's knowledge best characterized by a mentalistic stance, a teleological stance, or both? In this research, 5-month-old infants (N = 64, 50% female, 83% White) saw a novel eyeless agent consistently approach object-A as opposed to object-B. Although infants could always see both objects, a screen separated object-B from the agent. When object-B protruded above the screen, infants interpreted the agent's actions as revealing a preference for object-A over object-B. When object-B did not protrude above the screen, however, infants refrained from attributing such a preference: Consistent with mentalistic accounts, they reasoned that the agent's representation of the scene did not include object-B, and they used the agent's incomplete representation, non-egocentrically, to interpret its actions.

Toddlers draw broad negative inferences from wrongdoers' moral violations.

By 2 y of age, children possess expectations about several different moral principles. Building on these results, we asked whether children who observed a wrongdoer violate a principle would draw negative inferences from this violation about how the wrongdoer was likely to behave in other contexts. In four experiments, 25-mo-old toddlers (n = 152) first saw a wrongdoer harm a protagonist. When toddlers judged the wrongdoer's behavior to violate the principle of ingroup support or harm avoidance, they did not find it unexpected if the wrongdoer next violated the principle of fairness by dividing resources unfairly between two other protagonists (Exps. 2 and 3), but they did find it unexpected if the wrongdoer next acted generously by giving another protagonist most of a resource to be shared between them (Exp. 4). When toddlers did not construe the wrongdoer's harmful behavior as a moral violation, these responses reversed: They found it unexpected if the wrongdoer next acted unfairly (Exp. 1) but not if the wrongdoer next acted generously (Exp. 4). Detecting a moral violation thus lowered toddlers' assessment of the wrongdoer's moral character and brought down their expectations concerning the likelihood that the wrongdoer would perform: 1) obligatory actions required by other principles and 2) supererogatory or virtuous actions not required by the principles. Together, these findings expand our understanding of how young children evaluate others' moral characters, and they reveal how these evaluations, in turn, enable children to form sophisticated expectations about others' behavior in new contexts.

Five-month-old infants attribute inferences based on general knowledge to agents.

To make sense of others' actions, we generally consider what information is available to them. This information may come from different sources, including perception and inference. Like adults, young infants track what information agents can obtain through perception: If an agent directly observes an event, for example, young infants expect the agent to have information about it. However, no investigation has yet examined whether young infants also track what information agents can obtain through inference, by bringing to bear relevant general knowledge. Building on the finding that by 4 months of age most infants have acquired the physical rule that wide objects can fit into wide containers but not narrow containers, we asked whether 5-month-olds would expect an agent who was searching for a wide toy hidden in her absence to reach for a wide box as opposed to a narrow box. Infants looked significantly longer when the agent selected the narrow box, suggesting that they expected her (a) to share the physical knowledge that wide objects can fit only into wide containers and (b) to infer that the wide toy must be hidden in the wide box. Three additional conditions supported this interpretation. Together, these results cast doubt on two-system accounts of early psychological reasoning, which claim that infants' early-developing system is too inflexible and encapsulated to integrate inputs from other cognitive processes, such as physical reasoning. Instead, the results support one-system accounts and provide new evidence that young infants' burgeoning psychological-reasoning system is qualitatively similar to that of older children and adults.

How do the object-file and physical-reasoning systems interact? Evidence from priming effects with object arrays or novel labels.

How do infants reason about simple physical events such as containment, tube, and support events? According to the two-system model, two cognitive systems, the object-file (OF) and physical-reasoning (PR) systems, work together to guide infants' responses to these events. When an event begins, the OF system sends categorical information about the objects and their arrangements to the PR system. This system then categorizes the event, assigns event roles to the objects, and taps the OF system for information about features previously identified as causally relevant for the event category selected. All of the categorical and featural information included in the event's representation is interpreted by the PR system's domain knowledge, which includes core principles such as persistence and gravity. The present research tested a novel prediction of the model: If the OF system could be primed to also send, at the beginning of an event, information about an as-yet-unidentified feature, the PR system would then interpret this information using its core principles, allowing infants to detect core violations involving the feature earlier than they normally would. We examined this prediction using two types of priming manipulations directed at the OF system, object arrays and novel labels. In six experiments, infants aged 7-13 months (N = 304) were tested using different event categories and as-yet-unidentified features (color in containment events, height in tube events, and proportional distribution in support events) as well as different tasks (violation-of-expectation and action tasks). In each case, infants who were effectively primed reasoned successfully about the as-yet-unidentified feature, sometimes as early as six months before they would typically do so. These converging results provide strong support for the two-system model and for the claim that uncovering how the OF and PR systems represent and exchange information is essential for understanding how infants respond to physical events.

Infants expect leaders to right wrongs.

Anthropological and psychological research on direct third-party punishment suggests that adults expect the leaders of social groups to intervene in within-group transgressions. Here, we explored the developmental roots of this expectation. In violation-of-expectation experiments, we asked whether 17-mo-old infants (n = 120) would expect a leader to intervene when observing a within-group fairness transgression but would hold no particular expectation for intervention when a nonleader observed the same transgression. Infants watched a group of 3 bear puppets who served as the protagonist, wrongdoer, and victim. The protagonist brought in 2 toys for the other bears to share, but the wrongdoer seized both toys, leaving none for the victim. The protagonist then either took 1 toy away from the wrongdoer and gave it to the victim (intervention event) or approached each bear in turn without redistributing a toy (nonintervention event). Across conditions, the protagonist was either a leader (leader condition) or a nonleader equal in rank to the other bears (nonleader condition); across experiments, leadership was marked by either behavioral or physical cues. In both experiments, infants in the leader condition looked significantly longer if shown the nonintervention as opposed to the intervention event, suggesting that they expected the leader to intervene and rectify the wrongdoer's transgression. In contrast, infants in the nonleader condition looked equally at the events, suggesting that they held no particular expectation for intervention from the nonleader. By the second year of life, infants thus already ascribe unique responsibilities to leaders, including that of righting wrongs.

Do Infants in the First Year of Life Expect Equal Resource Allocations?

Recent research has provided converging evidence, using multiple tasks, of sensitivity to fairness in the second year of life. In contrast, findings in the first year have been mixed, leaving it unclear whether young infants possess an expectation of fairness. The present research examined the possibility that young infants might expect windfall resources to be divided equally between similar recipients, but might demonstrate this expectation only under very simple conditions. In three violation-of-expectation experiments, 9-month-olds (N = 120) expected an experimenter to divide two cookies equally between two animated puppets (1:1), and they detected a violation when she divided them unfairly instead (2:0). The same positive result was obtained whether the experimenter gave the cookies one by one to the puppets (Experiments 1-2) or first separated them onto placemats and then gave each puppet a placemat (Experiment 3). However, a negative result was obtained when four (as opposed to two) cookies were allocated: Infants looked about equally whether they saw a fair (2:2) or an unfair (3:1) distribution (Experiment 3). A final experiment revealed that 4-month-olds (N = 40) also expected an experimenter to distribute two cookies equally between two animated puppets (Experiment 4). Together, these and various control results support two broad conclusions. First, sensitivity to fairness emerges very early in life, consistent with claims that an abstract expectation of fairness is part of the basic structure of human moral cognition. Second, this expectation can at first be observed only under simple conditions, and speculations are offered as to why this might be the case.

Toddlers and infants expect individuals to refrain from helping an ingroup victim's aggressor.

Adults and older children are more likely to punish a wrongdoer for a moral transgression when the victim belongs to their group. Building on these results, in violation-of-expectation experiments (n = 198), we examined whether 2.5-year-old toddlers (Exps. 1 and 2) and 1-year-old infants (Exps. 3 and 4) would selectively expect an individual in a minimal group to engage in third-party punishment (TPP) for harm to an ingroup victim. We focused on an indirect form of TPP, the withholding of help. To start, children saw a wrongdoer steal a toy from a victim while a bystander watched. Next, the wrongdoer needed assistance with a task, and the bystander either helped or hindered her. The group memberships of the wrongdoer and the victim were varied relative to that of the bystander and were marked with either novel labels (Exps. 1 and 2) or novel outfits (Exps. 3 and 4). When the victim belonged to the same group as the bystander, children expected TPP: At both ages, they detected a violation when the bystander chose to help the wrongdoer. Across experiments, this effect held whether the wrongdoer belonged to the same group as the bystander and the victim or to a different group; it was eliminated when the victim belonged to a different group than the bystander, when groups were not marked, and when either no theft occurred or the wrongdoer was unaware of the theft. Toddlers and infants thus expect individuals to refrain from helping an ingroup victim's aggressor, providing further evidence for an early-emerging expectation of ingroup support.

Catastrophic individuation failures in infancy: A new model and predictions.

Comparison of infant findings from the physical-reasoning and object-individuation literatures reveals a contradictory picture. On the one hand, physical-reasoning results indicate that young infants can use featural information to guide their actions on objects and to detect interaction violations (when objects interact in ways that are not physically possible) as well as change violations (when objects spontaneously undergo featural changes that are not physically possible). On the other hand, object-individuation results indicate that young infants typically cannot use featural information to detect individuation violations (when the number of objects revealed at the end of an event is less than the number of objects introduced during the event). In this article, we attempt to reconcile these two bodies of research. In a new model of early individuation, we propose that two systems help infants individuate objects in physical events: the object-file and physical-reasoning systems. Under certain conditions, disagreements between the systems result in catastrophic individuation failures, leading infants to hold no expectation at all about how many objects are present. We report experiments with 9- to 11-month-old infants (N = 216) that tested predictions from the model. After two objects emerged in alternation from behind a screen, infants detected no violation when the screen was lowered to reveal no object. Similarly, after two objects emerged in alternation from inside a box, which was then shaken, infants detected no violation when the box remained silent, as though empty. We end with new directions, suggested by our model, for research on early object representations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Infants distinguish between leaders and bullies.

We examined whether 21-month-old infants could distinguish between two broad types of social power: respect-based power exerted by a leader (who might be an authority figure with legitimate power, a prestigious individual with merited power, or some combination thereof) and fear-based power exerted by a bully. Infants first saw three protagonists interact with a character who was either a leader (leader condition) or a bully (bully condition). Next, the character gave an order to the protagonists, who initially obeyed; the character then left the scene, and the protagonists either continued to obey (obey event) or no longer did so (disobey event). Infants in the leader condition looked significantly longer at the disobey than at the obey event, suggesting that they expected the protagonists to continue to obey the leader in her absence. In contrast, infants in the bully condition looked equally at the two events, suggesting that they viewed both outcomes as plausible: The protagonists might continue to obey the absent bully to prevent further harm, or they might disobey her because her power over them weakened in her absence. Additional results supported these interpretations: Infants expected obedience when the bully remained in the scene and could harm the protagonists if defied, but they expected disobedience when the order was given by a character with little or no power over the protagonists. Together, these results indicate that by 21 months of age, infants already hold different expectations for subordinates' responses to individuals with respect-based as opposed to fear-based power.

Infants expect ingroup support to override fairness when resources are limited.

Recent research suggests that the foundations of human moral cognition include abstract principles of fairness and ingroup support. We examined which principle 1.5-y-old infants and 2.5-y-old toddlers would prioritize when the two were pitted against each other. In violation-of-expectation tasks, a puppet distributor brought in either two (two-item condition) or three (three-item condition) items and faced two potential recipients, an ingroup and an outgroup puppet. In each condition, the distributor allocated two items in one of three events: She gave one item each to the ingroup and outgroup puppets (equal event), she gave both items to the ingroup puppet (favors-ingroup event), or she gave both items to the outgroup puppet (favors-outgroup event). Children in the two-item condition looked significantly longer at the equal or favors-outgroup event than at the favors-ingroup event, suggesting that when there were only enough items for the group to which the distributor belonged, children detected a violation if she gave any of the items to the outgroup puppet. In the three-item condition, in contrast, children looked significantly longer at the favors-ingroup or favors-outgroup event than at the equal event, suggesting that when there were enough items for all puppets present, children detected a violation if the distributor chose to give two items to one recipient and none to the other, regardless of which recipient was advantaged. Thus, infants and toddlers expected fairness to prevail when there were as many items as puppets, but they expected ingroup support to trump fairness otherwise.

Young infants expect an unfamiliar adult to comfort a crying baby: Evidence from a standard violation-of-expectation task and a novel infant-triggered-video task.

Do infants expect individuals to act prosocially toward others in need, at least in some contexts? Very few such expectations have been uncovered to date. In three experiments, we examined whether infants would expect an adult alone in a scene with a crying baby to attempt to comfort the baby. In the first two experiments, 12- and 4-month-olds were tested using the standard violation-of-expectation method. Infants saw videotaped events in which a woman was performing a household chore when a baby nearby began to cry; the woman either comforted (comfort event) or ignored (ignore event) the baby. Infants looked significantly longer at the ignore than at the comfort event, and this effect was eliminated if the baby laughed instead of cried. In the third experiment, 8-month-olds were tested using a novel forced-choice violation-of-expectation method, the infant-triggered-video method. Infants faced two computer monitors and were first shown that touching the monitors triggered events: One monitor presented the comfort event and the other monitor presented the ignore event. Infants then chose which event they wanted to watch again by touching the corresponding monitor. Infants significantly chose the ignore over the comfort event, and this effect was eliminated if the baby laughed. Thus, across ages and methods, infants provided converging evidence that they expected the adult to comfort the crying baby. These results indicate that expectations about individuals' actions toward others in need are already present in the first year of life, and, as such, they constrain theoretical accounts of early prosociality and morality.

Four-month-old infants individuate and track simple tools following functional demonstrations.

Two experiments examined whether 4-month-olds (n = 120) who were induced to assign two objects to different categories would then be able to take advantage of these contrastive categorical encodings to individuate and track the objects. In each experiment, infants first watched functional demonstrations of two tools, a masher and tongs (Experiment 1) or a marker and a knife (Experiment 2). Next, half the infants saw the two tools brought out alternately from behind a screen, which was then lowered to reveal only one of the tools (different-objects condition); the other infants saw similar events except that the same tool was shown on either side of the screen (same-object condition). In both experiments, infants in the different-objects condition looked reliably longer than those in the same-object condition, and this effect was eliminated if the demonstrations involved similar but non-functional actions. Together, these results indicate that infants (a) were led by the functional demonstrations they observed to assign the two tools to distinct categories, (b) recruited these categorical encodings to individuate and track the tools, and hence (c) detected a violation in the different-objects condition when the screen was lowered to reveal only one tool. Categorical information thus plays a privileged role in individuation and identity tracking from a very young age.

Explanation-based learning in infancy.

In explanation-based learning (EBL), domain knowledge is leveraged in order to learn general rules from few examples. An explanation is constructed for initial exemplars and is then generalized into a candidate rule that uses only the relevant features specified in the explanation; if the rule proves accurate for a few additional exemplars, it is adopted. EBL is thus highly efficient because it combines both analytic and empirical evidence. EBL has been proposed as one of the mechanisms that help infants acquire and revise their physical rules. To evaluate this proposal, 11- and 12-month-olds (n = 260) were taught to replace their current support rule (that an object is stable when half or more of its bottom surface is supported) with a more sophisticated rule (that an object is stable when half or more of the entire object is supported). Infants saw teaching events in which asymmetrical objects were placed on a base, followed by static test displays involving a novel asymmetrical object and a novel base. When the teaching events were designed to facilitate EBL, infants learned the new rule with as few as two (12-month-olds) or three (11-month-olds) exemplars. When the teaching events were designed to impede EBL, however, infants failed to learn the rule. Together, these results demonstrate that even infants, with their limited knowledge about the world, benefit from the knowledge-based approach of EBL.

Infants possess an abstract expectation of ingroup support.

One pervasive facet of human interactions is the tendency to favor ingroups over outgroups. Remarkably, this tendency has been observed even when individuals are assigned to minimal groups based on arbitrary markers. Why is mere categorization into a minimal group sufficient to elicit some degree of ingroup favoritism? We consider several accounts that have been proposed in answer to this question and then test one particular account, which holds that ingroup favoritism reflects in part an abstract and early-emerging sociomoral expectation of ingroup support. In violation-of-expectation experiments with 17-mo-old infants, unfamiliar women were first identified (using novel labels) as belonging to the same group, to different groups, or to unspecified groups. Next, one woman needed instrumental assistance to achieve her goal, and another woman either provided the necessary assistance (help event) or chose not to do so (ignore event). When the two women belonged to the same group, infants looked significantly longer if shown the ignore as opposed to the help event; when the two women belonged to different groups or to unspecified groups, however, infants looked equally at the two events. Together, these results indicate that infants view helping as expected among individuals from the same group, but as optional otherwise. As such, the results demonstrate that from an early age, an abstract expectation of ingroup support contributes to ingroup favoritism in human interactions.

Early False-Belief Understanding.

Intense controversy surrounds the question of when children first understand that others can hold false beliefs. Results from traditional tasks suggest that false-belief understanding does not emerge until about 4 years of age and constitutes a major developmental milestone in social cognition. By contrast, results from nontraditional tasks, which have steadily accumulated over the past 10 years, suggest that false-belief understanding is already present in infants (under age 2 years) and toddlers (age 2-3 years) and thus forms an integral part of social cognition from early in life. Here we first present an overview of the findings from nontraditional tasks. We then return to traditional tasks and argue that processing difficulties, rather than limitations in false-belief understanding, account for young children's failure at these tasks.

Two-and-a-half-year-olds succeed at a traditional false-belief task with reduced processing demands.

When tested with traditional false-belief tasks, which require answering a standard question about the likely behavior of an agent with a false belief, children perform below chance until age 4 y or later. When tested without such questions, however, children give evidence of false-belief understanding much earlier. Are traditional tasks difficult because they tap a more advanced form of false-belief understanding (fundamental-change view) or because they impose greater processing demands (processing-demands view)? Evidence that young children succeed at traditional false-belief tasks when processing demands are reduced would support the latter view. In prior research, reductions in inhibitory-control demands led to improvements in young children's performance, but often only to chance (instead of below-chance) levels. Here we examined whether further reductions in processing demands might lead to success. We speculated that: (i) young children could respond randomly in a traditional low-inhibition task because their limited information-processing resources are overwhelmed by the total concurrent processing demands in the task; and (ii) these demands include those from the response-generation process activated by the standard question. This analysis suggested that 2.5-y-old toddlers might succeed at a traditional low-inhibition task if response-generation demands were also reduced via practice trials. As predicted, toddlers performed above chance following two response-generation practice trials; toddlers failed when these trials either were rendered less effective or were used in a high-inhibition task. These results support the processing-demands view: Even toddlers succeed at a traditional false-belief task when overall processing demands are reduced.