Causal learning across domains

Five studies investigated (a) children's ability to use the dependent and independent probabilities of events to make causal inferences and (b) the interaction between such inferences and domain-specific knowledge. In Experiment 1, preschoolers used patterns of dependence and independence to make accurate causal inferences in the domains of biology and psychology. Experiment 2 replicated the results in the domain of biology with a more complex pattern of conditional dependencies. In Experiment 3, children used evidence about patterns of dependence and independence to craft novel interventions across domains. In Experiments 4 and 5, children's sensitivity to patterns of dependence was pitted against their domain-specific knowledge. Children used conditional probabilities to make accurate causal inferences even when asked to violate domain boundaries.     

The Role of Probability and Intentionality in Preschoolers' Causal Generalizations

Three experiments examined whether preschoolers recognize that the causal properties of objects generalize to new members of the same set given either deterministic or probabilistic data. Experiment 1 found that 3- and 4-year-olds were able to make such a generalization given deterministic data but were at chance when they observed probabilistic information. Five-year-olds reliably generalized in both situations. Experiment 2 found that 4-year-olds could make some probabilistic inferences, particularly when comparing sets that had no efficacy with sets in which some members had efficacy. Children had some difficulty discriminating between completely effective sets and stochastic ones. Experiment 3 examined whether 3- and 4-year-olds could reason about probabilistic data when provided with information about the experimenter's beliefs about causal outcomes. Children who were more successful on standard false-belief measures were more likely to respond as if the data were deterministic. These data suggest that children's probabilistic inferences develop into early elementary school, but preschoolers might have some understanding of probability when reasoning about causal generalization.     

The Blicket Within: Preschoolers' Inferences About Insides and Causes

Four experiments examined children's inferences about the relation between objects' internal parts and their causal properties. In Experiment 1, 4-year-olds recognized that objects with different internal parts had different causal properties, and those causal properties transferred if the internal part moved to another object. In Experiment 2, 4-year-olds made inferences from an object's internal parts to its causal properties without being given verbal labels for objects or being shown that insides and causal properties covaried. Experiment 3 found that 4-year-olds chose an object with the same internal part over one with the same external property when asked which object had the same causal property as the target (which had both the internal part and external property). Finally, Experiment 4 demonstrated that 4-year-olds made similar inferences from causal properties to internal parts, but 3-year-olds relied more on objects' external perceptual appearance. These results suggest that by the age of 4, children have developed an understanding of a relation between an artifact's internal parts and its causal properties.     

Young children infer causal strength from probabilities and interventions

We examine the interaction of two cues that children use to make judgments about cause-effect relations: probabilities and interventions. Children were shown a "detector" that lit up and played music when a block was placed on its surface. We varied the probabilistic effectiveness of the block, as well as whether the experimenter or the child was performing the interventions. In Experiment 1, we found that children can use probabilistic evidence to make inferences about causal strength. However, when the results of their own interventions are in conflict with the overall frequencies, preschoolers favor the results of their own interventions. In Experiment 2, children used probabilistic evidence to infer a hidden causal mechanism. Though they again gave preference to their own interventions, they did not do so when their interventions were explicitly confounded by an alternative cause.     

Bridging the gap: Causality-at-a-distance in children's categorization and inferences about internal properties

Previous research has shown that preschoolers extend labels and internal properties of objects based on those objects’ causal properties, even when the causal properties conflict with the objects’ perceptual appearance [Nazzi, T., & Gopnik, A. (2000). A shift in children's use of perceptual and causal cues to categorization. Developmental Science, 3, 389–396; Sobel, D. M., Yoachim, C. M., Gopnik, A., Meltzoff, A. N., & Blumenthal, E. J. (2007). The blicket within: Preschoolers’ inferences about insides and causes. Journal of Cognition and Development, 8, 159–182]. These studies, however, only presented causal relations that acted on contact. In two studies, contact causality was replaced by distance causality. In contrast to the contact causality case, 4- and 5-year-olds extended labels to objects with similar perceptual properties over objects with similar causal properties when those properties acted at a distance. When children were asked to make inferences about object's internal properties, they were more likely to make causal responses, with 5-year-olds doing so to a greater extent than 4-year-olds. In a second study, 4-year-olds registered causal properties that acted at a distance and used them to make inferences when no perceptual conflict was present. These results support a hypothesis that young children develop an understanding of the specific mechanisms that link causal relations.     

Serious fun: preschoolers engage in more exploratory play when evidence is confounded

Researchers, educators, and parents have long believed that children learn cause and effect relationships through exploratory play. However, previous research suggests that children are poor at designing informative experiments; children fail to control relevant variables and tend to alter multiple variables simultaneously. Thus, little is known about how children's spontaneous exploration might support accurate causal inferences. Here the authors suggest that children's exploratory play is affected by the quality of the evidence they observe. Using a novel free-play paradigm, the authors show that preschoolers (mean age: 57 months) distinguish confounded and unconfounded evidence, preferentially explore causally confounded (but not matched unconfounded) toys rather than novel toys, and spontaneously disambiguate confounded variables in the course of free play.     

Children’s causal inferences from indirect evidence: Backwards blocking and Bayesian reasoning in preschoolers

Previous research suggests that children can infer causal relations from patterns of events. However, what appear to be cases of causal inference may simply reduce to children recognizing relevant associations among events, and responding based on those associations. To examine this claim, in Experiments 1 and 2, children were introduced to a “blicket detector,” a machine that lit up and played music when certain objects were placed upon it. Children observed patterns of contingency between objects and the machine’s activation that required them to use indirect evidence to make causal inferences. Critically, associative models either made no predictions, or made incorrect predictions about these inferences. In general, children were able to make these inferences, but some developmental differences between 3- and 4-year-olds were found. We suggest that children’s causal inferences are not based on recognizing associations, but rather that children develop a mechanism for Bayesian structure learning. Experiment 3 explicitly tests a prediction of this account. Children were asked to make an inference about ambiguous data based on the base rate of certain events occurring. Four-year-olds, but not 3-year-olds were able to make this inference.     

Are Causal Structure and Intervention Judgments Inextricably Linked? A Developmental Study

The application of the formal framework of causal Bayesian Networks to children’s causal learning provides the motivation to examine the link between judgments about the causal structure of a system, and the ability to make inferences about interventions on components of the system. Three experiments examined whether children are able to make correct inferences about interventions on different causal structures. The first two experiments examined whether children’s causal structure and intervention judgments were consistent with one another. In Experiment 1, children aged between 4 and 8 years made causal structure judgments on a three‐component causal system followed by counterfactual intervention judgments. In Experiment 2, children’s causal structure judgments were followed by intervention judgments phrased as future hypotheticals. In Experiment 3, we explicitly told children what the correct causal structure was and asked them to make intervention judgments. The results of the three experiments suggest that the representations that support causal structure judgments do not easily support simple judgments about interventions in children. We discuss our findings in light of strong interventionist claims that the two types of judgments should be closely linked.     

How fantasy benefits young children's understanding of pretense

Sobel and Lillard (2001) demonstrated that 4-year-olds' understanding of the role that the mind plays in pretending improved when children were asked questions in a fantasy context. The present study investigated whether this fantasy effect was motivated by children recognizing that fantasy contains violations of real-world causal structure. In Experiment 1, 4-year-olds were shown a fantasy character engaged in ordinary actions or actions that violated causal knowledge. Children were more likely to say that a troll doll who was acting like but ignorant of the character was not pretending to be that character when read the violation story. Experiment 2 suggested that this difference was not caused by a greater interest in the violation story. Experiment 3 demonstrated a similar difference for characters engaged in social and functional violations that were possible in the real world. These data are consistent with the hypothesis that preschoolers use actions and appearance more than mental states to make judgments about pretense, but that those judgments can be influenced by the context in which the questions are presented.     

Children and Adults Use Gender and Age Stereotypes in Ownership Judgments

In everyday life, we are often faced with the problem of judging who owns an object. The current experiments show that children and adults base ownership judgments on group stereotypes, which relate kinds of people to kinds of objects. Moreover, the experiments show that reliance on stereotypes can override another means by which people make ownership judgments—inferring ownership from first possession. Experiment 1 replicates previous findings in showing that children and adults are strongly biased to assume that the first person to possess an object is its owner, while also demonstrating that the first-possession bias shows specificity to ownership. Experiment 2 shows that preschoolers and adults used gender stereotypes to make ownership judgments, and they do this even when stereotypes conflict with first possession. Experiment 3 reports similar findings but with age stereotypes. These findings reveal that stereotypes are a powerful means for making ownership judgments.     

Generalizing Kant's Distinction between Perfect and Imperfect Duties to Trust in Different Situations

Based on previous research that violations of perfect duties cause stronger correspondent inferences than violations of imperfect ones, the authors performed four experiments to generalize this effect to trust. In Experiment 1, abstract violations of perfect duties resulted in less trust than violations of imperfect ones for specific trust scenarios. In Experiments 2 and 3, the authors experimented with different levels of abstractness of the duty violations and obtained similar effects. Experiment 4 was concerned with generalizing further—from duty violations in one situation to trust in a different situation. Although mostly consistent with the findings from Experiments 1–3, the data also demonstrated partial generalization for violations of both perfect and imperfect duties.     

Spontaneous goal versus spontaneous trait inferences: How ideology shapes attributions and explanations

Past research documented liberals’ greater tendency than conservatives to take situational determinants of others’ actions into account when forming causal attributions, and conservatives’ greater tendency to seek consistency. We hypothesize that liberals (vs. conservatives) should be more likely to make spontaneous goal inferences (SGIs). Conservatives, however, should tend to implicitly infer invariant rather than variant characteristics from others’ behaviors, drawing spontaneous trait inferences (STIs) rather than SGIs. Experiment 1 and 2 supported those hypotheses by illustrating differences in the type of implicit inferences formed by liberals and conservatives in a false recognition paradigm common to the STI literature. Experiment 3 revealed similar differences in conservatives’ and liberals’ goal and trait inferences when making open-ended causal explanations for others’ actions.     

Word, thought, and deed: the role of object categories in children's inductive inferences and exploratory play

Previous research (e.g., S. A. Gelman & E. M. Markman, 1986; A. Gopnik & D. M. Sobel, 2000) suggests that children can use category labels to make inductive inferences about nonobvious causal properties of objects. However, such inductive generalizations can fail to predict objects' causal properties when (a) the property being projected varies within the category, (b) the category is arbitrary (e.g., things smaller than a bread box), or (c) the property being projected is due to an exogenous intervention rather than intrinsic to the object kind. In 4 studies, the authors showed that preschoolers (M = 48 months; range = 42-57 months) were sensitive to these constraints on induction and selectively engaged in exploration when evidence about objects' causal properties conflicted with inductive generalizations from the objects' kind to their causal powers. This suggests that the exploratory actions children generate in free play could support causal learning.     

Identifying expectations about the strength of causal relationships

When we try to identify causal relationships, how strong do we expect that relationship to be? Bayesian models of causal induction rely on assumptions regarding people’s a priori beliefs about causal systems, with recent research focusing on people’s expectations about the strength of causes. These expectations are expressed in terms of prior probability distributions. While proposals about the form of such prior distributions have been made previously, many different distributions are possible, making it difficult to test such proposals exhaustively. In Experiment 1 we used iterated learning—a method in which participants make inferences about data generated based on their own responses in previous trials—to estimate participants’ prior beliefs about the strengths of causes. This method produced estimated prior distributions that were quite different from those previously proposed in the literature. Experiment 2 collected a large set of human judgments on the strength of causal relationships to be used as a benchmark for evaluating different models, using stimuli that cover a wider and more systematic set of contingencies than previous research. Using these judgments, we evaluated the predictions of various Bayesian models. The Bayesian model with priors estimated via iterated learning compared favorably against the others. Experiment 3 estimated participants’ prior beliefs concerning different causal systems, revealing key similarities in their expectations across diverse scenarios.     

The role of preschoolers' social understanding in evaluating the informativeness of causal interventions

Preschoolers use information from interventions, namely intentional actions, to make causal inferences. We asked whether children consider some interventions to be more informative than others based on two components of an actor’s knowledge state: whether an actor possesses causal knowledge, and whether an actor is allowed to use their knowledge in a given situation. Three- and four-year-olds saw a novel toy that activated in the presence of certain objects. Two actors, one knowledgeable about the toy and one ignorant, each tried to activate the toy with an object. In Experiment 1, either the actors chose objects or the child chose for them. In Experiment 2, the actors chose objects blindfolded. Objects were always placed on the toy simultaneously, and thus were equally associated with the effect. Preschoolers’ causal inferences favored the knowledgeable actor’s object only when he was allowed to choose it (Experiment 1). Thus, children consider both personal and situational constraints on knowledge when evaluating the informativeness of causal interventions.     

Diversity-Based Reasoning in Children

One of the hallmarks of inductive reasoning by adults is the diversity effect, namely that people draw stronger inferences from a diverse set of evidence than from a more homogenous set of evidence. However, past developmental work has not found consistent diversity effects with children age 9 and younger. We report robust sensitivity to diversity in children as young as 5, using everyday stimuli such as pictures of objects with people. Experiment 1 showed the basic diversity effect in 5- to 9-year-olds. Experiment 2 showed that, like adults, children restrict their use of diversity information when making inferences about remote categories. Experiment 3 used other stimulus sets to overcome an alternate explanation in terms of sample size rather than diversity effects. Finally, Experiment 4 showed that children more readily draw on diversity when reasoning about objects and their relations with people than when reasoning about objects' internal, hidden properties, thus partially explaining the negative findings of previous work. Relations to cross-cultural work and models of induction are discussed.     

Semantic similarity of labels and inductive generalization: Taking a second look

Prior research suggests that preschoolers can generalize object properties based on category information conveyed by semantically-similar labels. However, previous research did not control for co-occurrence probability of labels in natural speech. The current studies re-assessed children’s generalization with semantically-similar labels. Experiment 1 indicated that adults made category-based inferences regardless of co-occurrence probability; however, 4-year-olds generalized with semantically-similar labels that co-occurred in child-directed speech (e.g., bunny–rabbit) but not with non-co-occurring labels (e.g., crocodile–alligator). Experiment 2 indicated that generalization with semantically-similar labels increased gradually between 4- and 6-years of age. These results are discussed in relation to theories of early learning.     

The role of learning data in causal reasoning about observations and interventions

Recent studies have shown that people have the capacity to derive interventional predictions for previously unseen actions from observational knowledge, a finding that challenges associative theories of causal learning and reasoning (e.g., Meder, Hagmayer, & Waldmann, 2008). Although some researchers have claimed that such inferences are based mainly on qualitative reasoning about the structure of a causal system (e.g., Sloman, 2005), we propose that people use both the causal structure and its parameters for their inferences. We here employ an observational trial-by-trial learning paradigm to test this prediction. In Experiment 1, the causal strength of the links within a given causal model was varied, whereas in Experiment 2, base rate information was manipulated while keeping the structure of the model constant. The results show that learners’ causal judgments were strongly affected by the observed learning data despite being presented with identical hypotheses about causal structure. The findings show furthermore that participants correctly distinguished between observations and hypothetical interventions. However, they did not adequately differentiate between hypothetical and counterfactual interventions.     

Going beyond the evidence: abstract laws and preschoolers' responses to anomalous data

Given minimal evidence about novel objects, children might learn only relationships among the specific entities, or they might make a more abstract inference, positing classes of entities and the relations that hold among those classes. Here we show that preschoolers (mean: 57 months) can use sparse data about perceptually unique objects to infer abstract physical causal laws. These newly inferred abstract laws were robust to potentially anomalous evidence; in the face of apparent counter-evidence, children (correctly) posited the existence of an unobserved object rather than revise the abstract laws. This suggests that children's ability to learn robust, abstract principles does not depend on extensive prior experience but can occur rapidly, on-line, and in tandem with inferences about specific relations.     

Where science starts: spontaneous experiments in preschoolers' exploratory play

Probabilistic models of expected information gain require integrating prior knowledge about causal hypotheses with knowledge about possible actions that might generate data relevant to those hypotheses. Here we looked at whether preschoolers (mean: 54 months) recognize “action possibilities” (affordances) in the environment that allow them to isolate variables when there is information to be gained. By manipulating the physical properties of the stimuli, we were able to affect the degree to which candidate variables could be isolated; by manipulating the base rate of candidate causes, we were able to affect the potential for information gain. Children’s exploratory play was sensitive to both manipulations: given unambiguous evidence children played indiscriminately and rarely tried to isolate candidate causes; given ambiguous evidence, children both selected (Experiment 1) and designed (Experiment 2) informative interventions.