Validation of an open source, remote web-based eye-tracking method (WebGazer) for research in early childhood.

Measuring eye movements remotely via the participant's webcam promises to be an attractive methodological addition to in-person eye-tracking in the lab. However, there is a lack of systematic research comparing remote web-based eye-tracking with in-lab eye-tracking in young children. We report a multi-lab study that compared these two measures in an anticipatory looking task with toddlers using WebGazer.js and jsPsych. Results of our remotely tested sample of 18-27-month-old toddlers (N = 125) revealed that web-based eye-tracking successfully captured goal-based action predictions, although the proportion of the goal-directed anticipatory looking was lower compared to the in-lab sample (N = 70). As expected, attrition rate was substantially higher in the web-based (42%) than the in-lab sample (10%). Excluding trials based on visual inspection of the match of time-locked gaze coordinates and the participant's webcam video overlayed on the stimuli was an important preprocessing step to reduce noise in the data. We discuss the use of this remote web-based method in comparison with other current methodological innovations. Our study demonstrates that remote web-based eye-tracking can be a useful tool for testing toddlers, facilitating recruitment of larger and more diverse samples; a caveat to consider is the larger drop-out rate.

Chimpanzees prepare for alternative possible outcomes.

When facing uncertainty, humans often build mental models of alternative outcomes. Considering diverging scenarios allows agents to respond adaptively to different actual worlds by developing contingency plans (covering one's bases). In a pre-registered experiment, we tested whether chimpanzees (Pan troglodytes) prepare for two mutually exclusive possibilities. Chimpanzees could access two pieces of food, but only if they successfully protected them from a human competitor. In one condition, chimpanzees could be certain about which piece of food the human experimenter would attempt to steal. In a second condition, either one of the food rewards was a potential target of the competitor. We found that chimpanzees were significantly more likely to protect both pieces of food in the second relative to the first condition, raising the possibility that chimpanzees represent and prepare effectively for different possible worlds.

Do chimpanzees reason logically?

Psychologists disagree about the development of logical concepts such as or and not. While some theorists argue that infants reason logically, others maintain that logical inference is contingent on linguistic abilities and emerges around age 4. In this Registered Report, we conducted five experiments on logical reasoning in chimpanzees. Subjects (N = 16; 10 females; M = 24 years) participated in the same setup that has been administered to children: the two-, three-, and four-cup-task. Chimpanzees performed above chance in the two-cup-, but not in the three-cup-task. Furthermore, chimpanzees selected the logically correct option more often in the test than the control condition of the four-cup-task. We discuss possible interpretations of these findings and conclude that our results are most consistent with non-deductive accounts.

Chimpanzees consider freedom of choice in their evaluation of social action.

Judgements of wrongdoing in humans often hinge upon an assessment of whether a perpetrator acted out of free choice: whether they had more than one option. The classic inhibitors of free choice are constraint (e.g. having your hands tied together) and ignorance (e.g. being unaware that an alternative exists). Here, across two studies, we investigate whether chimpanzees consider these factors in their evaluation of social action. Chimpanzees interacted with a human experimenter who handed them a non-preferred item of food, either because they were physically constrained from accessing the preferred item (Experiment 1) or because they were ignorant of the availability of the preferred item (Experiment 2). We found that chimpanzees were more likely to accept the non-preferred food and showed fewer negative emotional responses when the experimenter was physically constrained compared with when they had free choice. We did not, however, find an effect of ignorance on chimpanzee's evaluation. Freedom of choice factors into chimpanzees' evaluation of how they are treated, but it is unclear whether mental state reasoning is involved in this assessment.

Children understand subjective (undesirable) desires before they understand subjective (false) beliefs.

Our folk psychology is built around the ascription of beliefs (and related cognitive states) and desires (and related conative states). How and when children develop a concept of these different kinds of propositional attitudes has been the subject of a long-standing debate. Asymmetry accounts assume that children develop a conception of desires earlier than they develop a concept of beliefs. In contrast, the symmetry account assumes that conceptions of both kinds of attitudes are based on the same underlying capacity to ascribe subjective perspectives. Accordingly, a genuine subjective understanding of desires develops in tandem with subjective belief understanding. So far, existing evidence that tested these two accounts remains inconclusive, with inconsistent findings resulting from diverging methods. Therefore, the current study tested between the two accounts in a more systematic way. First, we used a particularly clear test case-value-incompatible (wicked) desires. Such desires are strongly subjective because they are desirable only from the agent's perspective but not from an objective perspective. Second, we probed children's ascription of such desires in the most direct and simplified ways. Third, we directly compared children's desire understanding with their ascription of subjective beliefs. Results revealed that young children were better in reasoning about subjective desires than about subjective beliefs. Desire reasoning was not correlated with subjective belief reasoning, and children did not have more difficulties in reasoning about strongly subjective wicked desires than about neutral desires. All in all, these findings are not in line with the predictions of the symmetry account but speak in favor of the asymmetry account.

How is the moral stance related to the intentional stance and group thinking?

The natural history of our moral stance told here in this commentary reveals the close nexus of morality and basic social-cognitive capacities. Big mysteries about morality thus transform into smaller and more manageable ones. Here, I raise questions regarding the conceptual, ontogenetic, and evolutionary relations of the moral stance to the intentional and group stances and to shared intentionality.

The ontogeny of intent-based normative judgments.

When evaluating norm transgressions, children begin to show some sensitivity to the agent's intentionality around preschool age. However, the specific developmental trajectories of different forms of such intent-based judgments and their cognitive underpinnings are still largely unclear. The current studies, therefore, systematically investigated the development of intent-based normative judgments as a function of two crucial factors: (a) the type of the agent's mental state underlying a normative transgression, and (b) the type of norm transgressed (moral versus conventional). In Study 1, 5- and 7-year-old children as well as adults were presented with vignettes in which an agent transgressed either a moral or a conventional norm. Crucially, she did so either intentionally, accidentally (not intentionally at all) or unknowingly (intentionally, yet based on a false belief regarding the outcome). The results revealed two asymmetries in children's intent-based judgments. First, all age groups showed greater sensitivity to mental state information for moral compared to conventional transgressions. Second, children's (but not adults') normative judgments were more sensitive to the agent's intention than to her belief. Two subsequent studies investigated this asymmetry in children more closely and found evidence that it is based on performance factors: children are able in principle to take into account an agent's false belief in much the same way as her intentions, yet do not make belief-based judgments in many existing tasks (like that of Study 1) due to their inferential complexity. Taken together, these findings contribute to a more systematic understanding of the development of intent-based normative judgment.

The Out-Group Homogeneity Effect Across Development: A Cross-Cultural Investigation.

The present studies investigated the out-group homogeneity effect in 5- and 8-year-old Israeli and German children (n = 150) and adults (n = 96). Participants were asked to infer whether a given property (either biological or psychological) was true of an entire group-either the participants' in-group ("Jews" or "Germans") or their out-group ("Arabs" or "Turks"). To that end, participants had to select either a homogenous or a heterogeneous sample of group members. It was found that across ages and countries, participants selected heterogeneous samples less often when inferring the biological properties of out-compared to in-group members. No effect was found regarding psychological properties. These findings have important implications for our understanding of the origins of intergroup bias.

Children's understanding of the aspectuality of intentions.

When children come to grasp the concept of intention is a central question in theory of mind research. Existing studies, however, present a puzzling picture. On the one hand, infants distinguish between intentional and accidental actions. On the other hand, previous work suggests that until 8 years of age children do not yet understand an essential property of intentions-their aspectuality. Intentions are aspectual in the sense that they refer to objects and actions only under specific aspects. For example, Oedipus married Jocasta without knowing that she was his mother. Thus, he intentionally married Jocasta but did not intentionally marry his mother. However, the negative findings from these studies may indicate performance limitations rather than competence limitations. The rationale of the current set of studies, therefore, was to test children's understanding of the aspectuality of intentions in a simplified, cognitively less demanding design. The participants, 5- and 6-year-olds (Study 1) and 4-year-olds (Study 2), were involved in simple games where they (or another agent) intentionally acted on objects that had an obvious first identity and a hidden second identity. Children either did or did not know about the toy's second identity at the moment of acting. After their actions, children were asked about their intentions regarding the toys' different identities. Results revealed that the 5- and 6-year-olds, but not the 4-year-olds, systematically considered how they (or another agent) represented the objects when making intentionality judgments. Thus, an understanding of aspectual intentions seems to develop at around the late preschool years-much earlier than previously assumed.

Eighteen-Month-Old Infants Correct Non-Conforming Actions by Others.

At around their third birthday, children begin to enforce social norms on others impersonally, often using generic normative language, but little is known about the developmental building blocks of this abstract norm understanding. Here, we investigate whether even toddlers show signs of enforcing on others interpersonally how "we" do things. In an initial dyad, 18-month-old infants learnt a simple game-like action from an adult. In two experiments, the adult either engaged infants in a normative interactive activity (stressing that this is the way "we" do it) or, as a non-normative control, marked the same action as idiosyncratic, based on individual preference. In a test dyad, infants had the opportunity to spontaneously intervene when a puppet partner performed an alternative action. Infants intervened, corrected, and directed the puppet more in the normative than in the non-normative conditions. These findings suggest that, during the second year of life, infants develop second-personal normative expectations about their partner's behavior ("You should do X!") in social interactions, thus making an important step toward understanding the normative structure of human cultural activities. These simple normative expectations will later be scaled up to group-minded and abstract social norms.

Is Implicit Theory of Mind a Real and Robust Phenomenon? Results From a Systematic Replication Study.

Recently, theory-of-mind research has been revolutionized by findings from novel implicit tasks suggesting that at least some aspects of false-belief reasoning develop earlier in ontogeny than previously assumed and operate automatically throughout adulthood. Although these findings are the empirical basis for far-reaching theories, systematic replications are still missing. This article reports a preregistered large-scale attempt to replicate four influential anticipatory-looking implicit theory-of-mind tasks using original stimuli and procedures. Results showed that only one of the four paradigms was reliably replicated. A second set of studies revealed, further, that this one paradigm was no longer replicated once confounds were removed, which calls its validity into question. There were also no correlations between paradigms, and thus, no evidence for their convergent validity. In conclusion, findings from anticipatory-looking false-belief paradigms seem less reliable and valid than previously assumed, thus limiting the conclusions that can be drawn from them.

Children's selective trust decisions: rational competence and limiting performance factors.

Recent research has amply documented that even preschoolers learn selectively from others, preferring, for example, reliable over unreliable and competent over incompetent models. It remains unclear, however, what the cognitive foundations of such selective learning are, in particular, whether it builds on rational inferences or on less sophisticated processes. The current study, therefore, was designed to test directly the possibility that children are in principle capable of selective learning based on rational inference, yet revert to simpler strategies such as global impression formation under certain circumstances. Preschoolers (N = 75) were shown pairs of models that either differed in their degree of competence within one domain (strong vs. weak or knowledgeable vs. ignorant) or were both highly competent, but in different domains (e.g., strong vs. knowledgeable model). In the test trials, children chose between the models for strength- or knowledge-related tasks. The results suggest that, in fact, children are capable of rational inference-based selective trust: when both models were highly competent, children preferred the model with the competence most predictive and relevant for a given task. However, when choosing between two models that differed in competence on one dimension, children reverted to halo-style wide generalizations and preferred the competent models for both relevant and irrelevant tasks. These findings suggest that the rational strategies for selective learning, that children master in principle, can get masked by various performance factors.

Are there signature limits in early theory of mind?

Current theory-of-mind research faces the challenge of reconciling two sets of seemingly incompatible findings: Whereas children come to solve explicit verbal false belief (FB) tasks from around 4years of age, recent studies with various less explicit measures such as looking time, anticipatory looking, and spontaneous behavior suggest that even infants can succeed on some FB tasks. In response to this tension, two-systems theories propose to distinguish between an early-developing system, tracking simple forms of mental states, and a later-developing system, based on fully developed concepts of belief and other propositional attitudes. One prediction of such theories is that the early-developing system has signature limits concerning aspectuality. We tested this prediction in two experiments. The first experiment showed (in line with previous findings) that 2- and 3-year-olds take into account a protagonist's true or false belief about the location of an object in their active helping behavior. In contrast, toddlers' helping behavior did not differentiate between true and false belief conditions when the protagonist's belief essentially involved aspectuality. Experiment 2 replicated these findings with a more stringent method designed to rule out more parsimonious explanations. Taken together, the current findings are compatible with the possibility that early theory-of-mind reasoning is subject to signature limits as predicted by the two-systems account.

Are great apes able to reason from multi-item samples to populations of food items?

Inductive learning from limited observations is a cognitive capacity of fundamental importance. In humans, it is underwritten by our intuitive statistics, the ability to draw systematic inferences from populations to randomly drawn samples and vice versa. According to recent research in cognitive development, human intuitive statistics develops early in infancy. Recent work in comparative psychology has produced first evidence for analogous cognitive capacities in great apes who flexibly drew inferences from populations to samples. In the present study, we investigated whether great apes (Pongo abelii, Pan troglodytes, Pan paniscus, Gorilla gorilla) also draw inductive inferences in the opposite direction, from samples to populations. In two experiments, apes saw an experimenter randomly drawing one multi-item sample from each of two populations of food items. The populations differed in their proportion of preferred to neutral items (24:6 vs. 6:24) but apes saw only the distribution of food items in the samples that reflected the distribution of the respective populations (e.g., 4:1 vs. 1:4). Based on this observation they were then allowed to choose between the two populations. Results show that apes seemed to make inferences from samples to populations and thus chose the population from which the more favorable (4:1) sample was drawn in Experiment 1. In this experiment, the more attractive sample not only contained proportionally but also absolutely more preferred food items than the less attractive sample. Experiment 2, however, revealed that when absolute and relative frequencies were disentangled, apes performed at chance level. Whether these limitations in apes' performance reflect true limits of cognitive competence or merely performance limitations due to accessory task demands is still an open question.

Are apes essentialists? Scope and limits of psychological essentialism in great apes.

Human reasoning is characterized by psychological essentialism (Gelman in The essential child: origins of essentialism in everyday thought. Oxford University Press, New York, 2003): when reasoning about objects, we distinguish between deep essential properties defining the object's kind and identity, and merely superficial features that can be changed without altering the object's identity. To date, it is unclear whether psychological essentialism is based on the acquisition of linguistic means (such as kind terms) and therefore uniquely human, or whether it is a more fundamental cognitive capacity which might be present also in the absence of language. In the present study, we addressed this question by testing whether, and if so, under which circumstances non-human apes also rely on psychological essentialism to identify objects. For this purpose, we adapted classical verbal transformation scenarios used in research on psychological essentialism (Keil in Concepts, kinds, and cognitive development. MIT Press, Cambridge, 1989) and implemented them in two nonverbal tasks: first, a box task, typically used to test object individuation (Experiment 1), and second, an object choice task, typically used to test object discrimination, object preferences and logical inferences (Experiments 2-4). Taken together, the results of the four experiments suggest that under suitable circumstances (when memory and other task demands are minimized), great apes engage in basic forms of essentialist reasoning. Psychological essentialism is thus possible also in the absence of language.

Young Children Understand the Role of Agreement in Establishing Arbitrary Norms-But Unanimity Is Key.

Human cultural groups value conformity to arbitrary norms (e.g., rituals, games) that are the result of collective "agreement." Ninety-six 3-year-olds had the opportunity to agree upon arbitrary norms with puppets. Results revealed that children normatively enforced these novel norms only on a deviator who had actually entered into the agreement (not on dissenting or ignorant individuals). Interestingly, any dissent during the norm-setting process (even if a majority of 90% preferred one course of action) prevented children from seeing a norm as established for anyone at all. These findings suggest that even young children understand something of the role of agreement in establishing mutually binding social norms, but that their notion of norm formation may be confined to conditions of unanimity.

Young children understand the normative force of standards of equal resource distribution.

Much recent research has shown that children are sensitive to basic principles of fair distribution of resources much earlier than previously assumed. Under appropriate circumstances, toddlers and sometimes even infants both expect that others will follow principles of equal distribution of resources and do so themselves. But from these findings it remains unclear whether young children understand and follow such principles of fairness as normative rules. The current study tested for such an understanding of the normative force of principles of resource distribution with a novel method. In the study, 3- and 5-year-olds witnessed how a (puppet) agent distributed resources jointly earned by herself and a fellow agent in equal or unequal ways. In one condition, the child herself or himself was this fellow agent, and in another condition it was an unrelated third party. Children spontaneously protested frequently against unfair distributions both when they themselves were affected and when another third party was affected (and never did so after fair distributions), with 5-year-olds doing so in more explicitly normative terms than 3-year-olds. These findings suggest that young children indeed understand principles of fair distribution as normatively binding regardless of whether they are personally affected or not.

Children protest moral and conventional violations more when they believe actions are freely chosen.

Young children spontaneously engage in normative evaluations of others' actions and actively enforce social norms. It is unclear, however, how flexible and integrated this early norm psychology is. The current study explored this question by testing whether children in their "real-life" normative evaluation of actions consider the actor's freedom of choice. Children witnessed different appropriate acts or mistakes (conventional or moral) by an agent under free or constrained circumstances. Across the two types of norms, participants protested less if a mistake occurred under constrained conditions than if it occurred under free conditions. Furthermore, they laid different weight on the actor's free choice in the two conditions. While refraining from blaming the agent for inappropriate constrained acts in the moral scenario, children still criticized a social conventional mistake under constrained conditions (although less than under free conditions), indicating that free choice is a more prominent factor in moral evaluations than in conventional evaluations. Thus, two domains of social cognition, normativity and theory of mind, are functionally integrated already early in development.

Explicit theory of mind is even more unified than previously assumed: belief ascription and understanding aspectuality emerge together in development.

Existing evidence suggests that children, when they first pass standard theory-of-mind tasks, still fail to understand the essential aspectuality of beliefs and other propositional attitudes: such attitudes refer to objects only under specific aspects. Oedipus, for example, believes Yocaste (his mother) is beautiful, but this does not imply that he believes his mother is beautiful. In three experiments, 3- to 6-year-olds' (N = 119) understanding of aspectuality was tested with a novel, radically simplified task. In contrast to all previous findings, this task was as difficult as and highly correlated with a standard false belief task. This suggests that a conceptual capacity more unified than previously assumed emerges around ages 4-5, a full-fledged metarepresentational scheme of propositional attitudes.