Synchrony refers to the coordinated interplay of behavioural and physiological signals that reflect the bi-directional attunement of one partner to the other’s psychophysiological, cognitive, emotional, and behavioral state. In mother-child relationships, a synchronous pattern of interaction indicates parental sensitivity. Parenting stress has been shown to undermine mother-child behavioural synchrony. However, it has yet to be discerned whether parenting stress affects brain-to-brain synchrony during everyday joint activities. Here, we show that greater parenting stress is associated with less brain-to-brain synchrony in the medial left cluster of the prefrontal cortex when mother and child engage in a typical dyadic task of watching animation videos together. This brain region overlaps with the inferior frontal gyrus, the frontal eye field, and the dorsolateral prefrontal cortex, which are implicated in inference of mental states and social cognition. Our result demonstrates the adverse effect of parenting stress on mother-child attunement that is evident at a brain-to-brain level. Mother-child brain-to-brain asynchrony may underlie the robust association between parenting stress and poor dyadic co-regulation. We anticipate our study to form the foundation for future investigations into mechanisms by which parenting stress impairs the mother-child relationship.

Significance We provide an experimental demonstration that young infants possess abstract biological expectations about animals. Our findings represent a major breakthrough in the study of the foundations of human knowledge. In four experiments, 8-mo-old infants expected novel objects they categorized as animals to have filled insides. Thus, infants detected a violation when objects that were self-propelled and agentive were revealed to be hollow, or when an object that was self-propelled and furry rattled when shaken, as though mostly hollow. We describe possible characterizations of infants’ expectations about animals’ insides, including a characterization that emphasizes human predator–prey adaptations. We also discuss how infants’ expectation that animals have insides lays a foundation for the development of more advanced biological knowledge.

IntroductionConsider the following scene: A man wearing a backpack is pacing leisurely back and forth in a large airport room. As he strolls, he occasionally crosses his arms, twirls the dangling straps of his backpack, or stuffs his hands in his pant pockets. At one point, he sits down, takes off his backpack, and removes from it a bag filled with assorted gummy bears; as he peers intently inside the bag, he selects and eats, one at a time, five red gummy bears.As adults, we would have no difficulty interpreting the man's actions. We might view his initial actions-pacing, crossing his arms, and so on-as intentional (as opposed to accidental) though not as directed toward any particular goal. In contrast, we might perceive his subsequent actions-removing the bag of gummy bears from his backpack and eating five red ones in succession-as both intentional and goal-directed. In analyzing these actions, we might build an explanation that attributes to the man a causally coherent set of motivational and epistemic mental states: He wants to eat gummy bears, he is particularly fond of red ones, and so when he spies one in the bag, he removes it and eats it.Next, consider a new scene: As the man is happily chewing on red gummy bears, he notices a second man approaching who is carrying two heavy suitcases. At this point, our scene might unfold according to different scenarios. In one, the first man greets the second man, offers to carry one of the suitcases, and holds out his bag of gummy bears. In another scenario, the first man continues to watch the second man but makes no move to approach him. In yet another scenario, the first man sticks out a leg to trip the second man, causing him to fall heavily.As adults, we would interpret and evaluate the first man's actions in the three scenarios very differently. In the first scenario, we might infer that the two men have a social group in common: They might be friends, coworkers, or relatives, for example. In the second scenario, we 3 would conclude that the two men are strangers. In both the first and second scenarios, we would view the first man's behavior as acceptable: Offering help and sharing food are expected prosocial behaviors in interactions with ingroup, but not outgroup, individuals. In contrast, the first man's behavior in the third scenario would seem to us beyond the pale: Unprovoked harmful actions, even against outgroup individuals, are generally viewed as unacceptable. We would categorize the first man as an antisocial lout, and we might file away distinctive characteristics as possible markers of a social group to be avoided in the future.Our discussion of the two scenes above illustrates the rich analyses that adults spontaneously engage in when watching others act. What are the developmental origins of these interpretations? Over the past 25 years, there has been a great deal of research on social cognition in infancy. This research can be roughly organized into two sets of questions that map neatly onto the two scenes above. First, when watching an agen...

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.theory of mind | psychological reasoning | false-belief understanding | inhibitory control | information-processing resources

The psychological capacity to recognize that others may hold and act on false beliefs has been proposed to reflect an evolved, species-typical adaptation for social reasoning in humans; however, controversy surrounds the developmental timing and universality of this trait. Cross-cultural studies using elicited-response tasks indicate that the age at which children begin to understand false beliefs ranges from 4 to 7 years across societies, whereas studies using spontaneous-response tasks with Western children indicate that false-belief understanding emerges much earlier, consistent with the hypothesis that false-belief understanding is a psychological adaptation that is universally present in early childhood. To evaluate this hypothesis, we used three spontaneous-response tasks that have revealed early falsebelief understanding in the West to test young children in three traditional, non-Western societies: Salar (China), Shuar/Colono (Ecuador) and Yasawan (Fiji). Results were comparable with those from the West, supporting the hypothesis that false-belief understanding reflects an adaptation that is universally present early in development.