Person:

Schachner, Adena Michelle

Dance is a universal and ancient human behavior; however, our understanding of the basis of this behavior is surprisingly weak. In this dissertation, I explore the cognitive and evolutionary foundations of human dance, providing evidence of two ways in which the production and perception of dance actions are rooted in the functions of more general cognitive systems.In doing so, I aim to both inform our understanding of dance, and use the study of dance to elucidate broader issues in cognition. Chapter 1 demonstrates that the ability to entrain, or move in time with an auditory beat, is not unique to humans. In addition, across hundreds of species, I find that all animals able to entrain can also vocally imitate sound. This supports the hypothesis that entrainment relies on cognitive machinery that originally evolved to support vocal imitation. Chapter 2 investigates the perception of dance-like actions. Previous work shows that we infer the goals of observed actions by calculating their efficiency as a means to external effects, like reaching an object or location. However, dance actions typically lack an external effect or external goal. In two experiments, I show that for dance-like actions, adults infer that the agents’ goal is simply to produce the movements themselves. Furthermore, this inference is driven by the actions’ inefficiency as a means to external goals. This inefficiency effectively rules out external goals, making movement-based goals the best explanation. Thus, perception of both dance and non-dance actions appears to rely the same type of efficiency-based goal inference. Chapter 3 builds on these findings, showing that the inference that the movements are the goal is closely related to our concept of dance. First, I find that participants view movement-based goals as more consistent with dance than with other activities. Second, I find that simply construing actions as having movement-based goals leads participants to view the actions as more dancelike, even when all participants have seen the exact same actions. Thus, even our categorization of actions as dance versus non-dance is rooted in the same cognitive processes as support our understanding of other intentional actions.

Recent reports have suggested that many published results are unreliable. To increase the reliability and accuracy of published papers, multiple changes have been proposed, such as changes in statistical methods. We support such reforms. However, we believe that the incentive structure of scientific publishing must change for such reforms to be successful. Under the current system, the quality of individual scientists is judged on the basis of their number of publications and citations, with journals similarly judged via numbers of citations. Neither of these measures takes into account the replicability of the published findings, as false or controversial results are often particularly widely cited. We propose tracking replications as a means of post-publication evaluation, both to help researchers identify reliable findings and to incentivize the publication of reliable results. Tracking replications requires a database linking published studies that replicate one another. As any such data- base is limited by the number of replication attempts published, we propose establishing an open-access journal dedicated to publishing replication attempts. Data quality of both the database and the affiliated journal would be ensured through a combination of crowd- sourcing and peer review. As reports in the database are aggregated, ultimately it will be possible to calculate replicability scores, which may be used alongside citation counts to evaluate the quality of work published in individual journals. In this paper, we lay out a detailed description of how this system could be implemented, including mechanisms for compiling the information, ensuring data quality, and incentivizing the research community to participate.

Infants and adults are thought to infer the goals of observed actions by calculating the actions’ efficiency as a means to particular external effects, like teaching an object or location. However, many intentional actions lack an external effect or external goal (e.g. dance). We show that for these actions, adults infer that the agents’ goal is to produce the movements themselves: Movements are seen as the intended outcome, not just a means to an end. We test what drives observers to infer such movement-based goals, hypothesizing that observers infer movement-based goals to explain actions that are clearly intentional, but are not an efficient means to any plausible external goal. In three experiments, we separately manipulate intentionality and efficiency, equating for movement trajectory, perceptual features, and external effects. We find that participants only infer movement based goals when the actions are intentional and are not an efficient means to external goals. Thus, participants appear to infer that movements are the goal in order to explain otherwise mysterious intentional actions. These findings expand models of goal inference to account for intentional yet ‘irrational’ actions, and suggest a novel explanation for over imitation as emulation of movement-based goals.

Young children regularly engage in musical activities, but the effects of early music education on children’s cognitive development are unknown. While some studies have found associations between musical training in childhood and later nonmusical cognitive outcomes, few randomized controlled trials (RCTs) have been employed to assess causal effects of music lessons on child cognition and no clear pattern of results has emerged. We conducted two RCTs  with preschool children investigating the cognitive effects of a brief series of music classes, as  compared to a similar but non-musical form of arts instruction (visual arts classes, Experiment 1) or to a no-treatment control (Experiment 2). Consistent with typical preschool arts enrichment programs, parents attended classes with their children, participating in a variety of developmentally appropriate arts activities. After six weeks of class, we assessed children’s skills  in four distinct cognitive areas in which older arts-trained students have been reported to excel: spatial-navigational reasoning, visual form analysis, numerical discrimination, and receptive vocabulary. We initially found that children from the music class showed greater spatial-navigational ability than did children from the visual arts class, while children from the visual arts class showed greater visual form analysis ability than children from the music class (Experiment 1). However, a partial replication attempt comparing music training to a no-treatment control failed to confirm these findings (Experiment 2), and the combined results of  the two experiments were negative: overall, children provided with music classes performed no better than those with visual arts or no classes on any assessment. Our findings underscore the need for replication in RCTs, and suggest caution in interpreting the positive findings from past studies of cognitive effects of music instruction.