David M. Sobel

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 3and 4year-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. Fouryear-olds, but not 3-year-olds were able to make this inference.

Action Understanding in the Superior Temporal Sulcus Region

The posterior superior temporal sulcus (STS) region plays an important role in the perception of social acts, although its full role has not been completely clarified. This functional magnetic resonance imaging experiment examined activity in the STS region as participants viewed actions that were congruent or incongruent with intentions established by a previous emotional context. Participants viewed an actress express either a positive or a negative emotion toward one of two objects and then subsequently pick up one of them. If the object that was picked up had received positive regard, or if the object that was not picked up had received negative regard, the action was congruent; otherwise, the action was incongruent. Activity in the right posterior STS region was sensitive to the congruency between the action and the actresss emotional expression (i.e., STS activity was greater on incongruent than on congruent trials). These findings suggest that the posterior STS represents not only biological motion, but also how another persons motion is related to his or her intentions.

Children's beliefs about the fantasy/reality status of hypothesized machines

Four-year-olds, 6-year-olds, and adults were asked to make judgments about the reality status of four different types of machines: real machines that children and adults interact with on a daily basis, real machines that children and adults interact with rarely (if at all), and impossible machines that violated a real-world physical or biological causal law. Adults generally categorized all of the machines accurately. Both groups of children categorized familiar possible machines as real, but were agnostic as to the fantasy status of unfamiliar possible machines. Children generally responded that both kinds of impossible machines were make-believe, but 4-year-olds were more likely to make these accurate judgments for the physical than biological items, different from the older children and adults (whose responses were similar). These data suggest that childrens judgments about the possibility of machines are not strictly limited by first-hand experience. Young childrens domain-specific causal knowledge interacts with their understanding of the fantasy/reality distinction to constrain their inferences in a rational way.

Exploring the coherence of young children' s explanatory abilities: Evidence from generating counterfactuals

Researchers who advocate the hypothesis that cognitive development is akin to theory formation have also suggested that young children possess distinct systems for explaining physical, psychological, and biological principles (see, e.g., Wellman & Gelman, 1992). One way this has been investigated is by examining how children explain human action: Children explain intentional and accidental actions by appealing to psychological principles, and explain impossible physical or biological action in terms of the underlying principles of those domains (Schult & Wellman, 1997). The current investigation examined the coherence of children’ s explanatory systems by eliciting explanations of possible and impossible physical, psychological, and biological events. Then, in a separate set of stories, children were asked to generate counterfactual alternatives for characters who wanted to perform an event, but did not, either because of a mishap or because the event was impossible. Overall, children were better at generating explanations for why events were impossible than recognizing that no alternative could be generated for impossible events. However, there was some evidence that children’ s explanatory abilities predicted whether they could correctly reject cases where no counterfactual alternative could be generated. The results lend support to the hypothesis that children’ s causal knowledge is coherently organized in domain-specific knowledge structures.

Infants Track the Reliability of Potential Informants

Across two eye-tracking experiments, we showed that infants are sensitive to the statistical reliability of informative cues and selective in their use of information generated by such cues. We familiarized 8-month-olds with faces (Experiment 1) or arrows (Experiment 2) that cued the locations of animated animals with different degrees of reliability. The reliable cue always cued a box containing an animation, whereas the unreliable cue cued a box that contained an animation only 25% of the time. At test, infants searched longer in the boxes that were reliably cued, but did not search longer in the boxes that were unreliably cued. At generalization, when boxes were cued that never contained animations before, only infants in the face experiment followed the reliable cue. These results provide the first evidence that even young infants can track the reliability of potential informants and use this information judiciously to modify their future behavior.

Domain Generality and Specificity in Children's Causal Inference About Ambiguous Data

In 5 experiments the authors examined childrens understanding of causal mechanisms and their reasoning about base rates across domains of knowledge. Experiment 1 showed that 3-year-olds interpret objects activating a machine differently from a novel agent liking each object; children are more likely to treat the latter as indicating the objects with the causal property possessed an internal property. Experiment 2 suggested that 3-year-olds potentially use this mechanistic knowledge to reason about ambiguous data in terms of base rate information. Experiments 3, 4a, and 4b showed that these inferences are not the result of children being more interested in an agents desires. Instead, children integrate domain-specific knowledge (i.e., reasoning about an agent vs. a machine) with the nature of that inference within that domain (i.e., reasoning about desires vs. other mental states). The authors suggest that a particular computational approach, based on Bayesian inference, best describes these inferences. This approach offers a description of how children might integrate domain-specific mechanism knowledge into a more general model of causal inference based on observing covariation data among events.

60 GHz CMOS radio for Gb/s wireless LAN

The availability of 7 GHz of unlicensed spectrum in the 60 GHz band motivates the design of a low-cost 60 GHz wireless LAN (WLAN) system. System and circuit barriers to a low cost implementation are discussed and various solutions are proposed.

Ambiguous Figure Perception and Theory of Mind Understanding in Children with Autistic Spectrum Disorders.

Researchers in early social-cognition have found that the ability to reverse an ambiguous figure is correlated with success on theory of mind tasks (e.g. Gopnik & Rosati, 2001). The present experiment examined children with autistic spectrum disorders (ASD) without mental delay to see whether a similar relationship existed. Ropar, Mitchell, and Ackroyd (2003) demonstrated that children with ASD with mental delay were impaired on theory of mind tasks, but were as likely as mentally delayed controls to generate both interpretations of an ambiguous figure when informed of its ambiguity. The present study replicated this finding on children with ASD without mental delay. However, overall perception of ambiguous figures was different. These children were less likely to spontaneously generate both interpretations of the figure, and more likely to perseverate on a single interpretation than the comparison children. Like Ropar et al., we found no correlation between theory of mind and informed reversals, but spontaneous reversals were correlated with performance on an advanced theory of mind task. These data suggest that reversals of ambiguous figures are linked to higher-level representational abilities, which might also be involved in social functioning, and impaired in children with ASD.

The importance of decision making in causal learning from interventions

Recent research has focused on how interventions benefit causal learning. This research suggests that the main benefit of interventions is in the temporal and conditional probability information that interventions provide a learner. But when one generates interventions, one must also decide what interventions to generate. In three experiments, we investigated the importance of these decision demands to causal learning. Experiment 1 demonstrated that learners were better at learning causal models when they observed intervention data that they had generated, as opposed to observing data generated by another learner. Experiment 2 demonstrated the same effect between self-generated interventions and interventions learners were forced to make. Experiment 3 demonstrated that when learners observed a sequence of interventions such that the decision-making process that generated those interventions was more readily available, learning was less impaired. These data suggest that decision making may be an important part of causal learning from interventions.

“They Danced Around in My Head and I Learned Them”: Children's Developing Conceptions of Learning

Two studies examined how 3–6-year-olds understand the process of learning. In study 1 examined how children spontaneously talk about learning via a CHILDES language analysis. Talk about the learning process increased between the ages of 3–5. Talk specifically about learning in terms of desire decreased during this period. This suggests the possibility that desire is important to childrens initial understanding of learning, and children develop an understanding that various mental states including desire, attention, and intention, play a role in the learning process. In Study 2, we presented 4- and 6-year-olds with a set of stories designed to test their understanding of the role of these mental states. In both their judgments about whether someone learns and their justifications of their responses, younger children relied more on the characters desires whereas older children were more likely to integrate desire, attention, and intention together. These data suggest that childrens understanding of the process of learning is developing during the early elementary school years.