Reasoning about ‘irrational’ actions: When intentional movements cannot be explained, the movements themselves are seen as the goal

Toward a neuroaesthetics of interactions: Insights from dance on the aesthetics of individual and interacting bodies

Neuroaesthetics has advanced our understanding of the neural processes underlying human aesthetic evaluation of crafted and natural entities, including the human body. While much research has examined the neurocognitive mechanisms behind evaluating "single-body" forms and movements, the perception and aesthetic evaluation of multiple individuals moving together have only recently gained attention. This review examines the neural foundations of static and dynamic body perception and how neural representations of observed and executed movements influence their aesthetic evaluation. Focusing on dance, it describes the role of stimulus features and individual characteristics in movement aesthetics. We review neural systems supporting visual processing of social interactions and propose a role for these systems in the aesthetic evaluation of interpersonal interactions, defined as the neuroaesthetics of interactions. Our goal is to highlight the benefits of integrating insights and methods from social cognition, neuroscience, and neuroaesthetics to understand mechanisms underlying interaction aesthetics, while addressing future challenges.

15-Month-Olds' Understanding of Imitation in Social and Instrumental Contexts

From early in development, humans use imitation to express social engagement, to understand social affiliations, and to learn from others. Nevertheless, the social and instrumental goals that drive imitation in everyday and pedagogical contexts are highly intertwined. What cues might infants use to infer that a social goal is driving imitation? Here we use minimal and tightly controlled visual displays to evaluate 15-month-olds' attribution of social goals to imitation. In particular, we ask whether they see the very same simple, imitative actions shared between two agents as social or nonsocial when those actions occur in the absence or presence of intentional cues such as obstacles, object goals, and efficient, causally effective action. Our results suggest that infants' attributing social value to imitation only in the absence of such intentional cues may be a signature of humans' early understanding of imitation. We propose, moreover, that a systematic evaluation of a set of simple scenarios that probe candidate principles of early knowledge about social and instrumental actions and goals is possible and promises to inform our understanding of the foundational knowledge on which human social learning is built, as well as to aid the building of human-like artificial intelligence.

What is in an action? Preschool children predict that agents take previous paths and not previous goals

Developmental science has experienced a vivid debate on whether young children prioritize goals over means in their prediction of others' actions. Influential developmental theories highlight the role of goal objects for action understanding. Yet, recent infant studies report evidence for the opposite. The empirical evidence is therefore inconclusive. The current study advanced this debate by assessing preschool children's verbal predictions of others' actions. In five experiments (N = 302), we investigated whether preschool children and adults predict agents to move towards their previous goal (that is, show goal-related predictions) or predict agents to move along the same movement path that they pursued before. While Experiments 1a, 1b and 1c presented young children and adults with animated agents, Experiments 2a and 2b presented participants with human grasping action. An integrative analysis across experiments revealed that children were more likely to predict the agent to move along the same movement path, Z = -4.574, p ≤ 0.0001 (r = 0.304). That is, preschool children were more likely to predict that agents would move along the same trajectory even though this action would lead to a new goal object. Thus, our findings suggest that young children's action prediction relies on the detection of spatial and movement information. Overall, we discuss our findings in terms of theoretical frameworks that conceive of action understanding as an umbrella term that comprises different forms and facets in which humans understand others' actions. RESEARCH HIGHLIGHTS: We investigated whether preschool children predict agents to move towards their previous goal or to move along the same movement path that they pursued before. Unlike adults, preschool children predicted that agents would move along the same trajectory even though this action would lead to a new goal. Adults' goal-based predictions were affected from contextual details, whereas children systematically made path-based predictions. Young children's action prediction relies on the detection of spatial and movement information.

Infants rationally infer the goals of other people's reaches in the absence of first-person experience with reaching actions

Does knowledge of other people's minds grow from concrete experience to abstract concepts? Cognitive scientists have hypothesized that infants' first-person experience, acting on their own goals, leads them to understand others' actions and goals. Indeed, classic developmental research suggests that before infants reach for objects, they do not see others' reaches as goal-directed. In five experiments (N = 117), we test an alternative hypothesis: Young infants view reaching as undertaken for a purpose but are open-minded about the specific goals that reaching actions are aimed to achieve. We first show that 3-month-old infants, who cannot reach for objects, lack the expectation that observed acts of reaching will be directed to objects rather than to places. Infants at the same age learned rapidly, however, that a specific agent's reaching action was directed either to an object or to a place, after seeing the agent reach for the same object regardless of where it was, or to the same place regardless of what was there. In a further experiment, 3-month-old infants did not demonstrate such inferences when they observed an actor engaging in passive movements. Thus, before infants have learned to reach and manipulate objects themselves, they infer that reaching actions are goal-directed, and they are open to learning that the goal of an action is either an object or a place. RESEARCH HIGHLIGHTS: In the present experiments, 3-month-old prereaching infants learned to attribute either object goals or place goals to other people's reaching actions. Prereaching infants view agents' actions as goal-directed, but do not expect these acts to be directed to specific objects, rather than to specific places. Prereaching infants are open-minded about the specific goal states that reaching actions aim to achieve.

Aesthetic Motivation Impacts Judgments of Others' Prosociality and Mental Life

The ability to infer others' prosocial vs. antisocial behavioral tendencies from minimal information is core to social reasoning. Aesthetic motivation (the value or appreciation of aesthetic beauty) is linked with prosocial tendencies, raising the question of whether this factor is used in interpersonal reasoning and in the attribution of mental capacities. We propose and test a model of this reasoning, predicting that evidence of others' aesthetic motivations should impact judgments of others' prosocial (and antisocial) tendencies by signaling a heightened capacity for emotional experience. In a series of four pre-registered experiments (total N = 1440), participants saw pairs of characters (as photos/vignettes), and judged which in each pair showed more of a mental capacity of interest. Distractor items prevented participants from guessing the hypothesis. For one critical pair of characters, both characters performed the same activity (music listening, painting, cooking, exercising, being in nature, doing math), but one was motivated by the activities' aesthetic value, and the other by its functional value. Across all activities, participants robustly chose aesthetically-motivated characters as more likely to behave compassionately (Exp. 1; 3), less likely to behave selfishly/manipulatively (Exp. 1; 3), and as more emotionally sensitive, but not more intelligent (Exp. 2; 3; 4). Emotional sensitivity best predicted compassionate behavior judgements (Exp. 3). Aesthetically-motivated characters were not reliably chosen as more helpful; intelligence best predicted helpfulness judgements (Exp. 4). Evidence of aesthetic motivation conveys important social information about others, impacting fundamental interpersonal judgments about others' mental life and social behavior.

Seeing and understanding epistemic actions

Many actions have instrumental aims, in which we move our bodies to achieve a physical outcome in the environment. However, we also perform actions with epistemic aims, in which we move our bodies to acquire information and learn about the world. A large literature on action recognition investigates how observers represent and understand the former class of actions; but what about the latter class? Can one person tell, just by observing another person's movements, what they are trying to learn? Here, five experiments explore epistemic action understanding. We filmed volunteers playing a "physics game" consisting of two rounds: Players shook an opaque box and attempted to determine i) the number of objects hidden inside, or ii) the shape of the objects inside. Then, independent subjects watched these videos and were asked to determine which videos came from which round: Who was shaking for number and who was shaking for shape? Across several variations, observers successfully determined what an actor was trying to learn, based only on their actions (i.e., how they shook the box)-even when the box's contents were identical across rounds. These results demonstrate that humans can infer epistemic intent from physical behaviors, adding a new dimension to research on action understanding.

Infants are sensitive to the social signaling value of shared inefficient behaviors

Actions that are blatantly inefficient to achieve non-social goals are often used to convey information about agents' social affiliation, as in the case of rituals. We argue that when reproduced, actions that are individually inefficient acquire a social signaling value owing to the mechanisms that support humans' intuitive analysis of actions. We tested our hypothesis on 15-month-old infants who were familiarized with an agent that reproduced or merely observed the actions of efficient and inefficient individuals. Subsequently, we measured the infants' expectations of the agent's preferences for efficient and inefficient individuals. Our results confirmed that when agents act alone, infants expect a third-party to prefer efficient over inefficient agents. However, this pattern is entirely flipped if the third-party reproduces the agents' actions. In that case, infants expect inefficient agents to be preferred over efficient ones. Thus, reproducing actions whose rational basis is elusive can serve a critical social signaling function, accounting for why such behaviors are pervasive in human groups.

Finding Structure in Modern Dance

Research has shown that both adults and children organize familiar activity into discrete units with consistent boundaries, despite the dynamic, continuous nature of everyday experiences. However, less is known about how observers segment unfamiliar event sequences. In the current study, we took advantage of the novelty that is inherent in modern dance. Modern dance features natural human motion but does not contain canonical goals-therefore, observers cannot recruit prior goal-related knowledge to segment it. Our main aims were to identify whether observers segment modern dance into the steps intended by the dancers, and what types of cues contribute to segmentation under these circumstances. Experiment 1 used a classic event segmentation task and found that adults were able to consistently identify only a few of the dancers' intended steps. Experiment 2 tested adults in an offline labeling task. Results showed that steps which could more easily be labeled offline in Experiment 2 were more likely to be segmented online in Experiment 1.

Not Playing by the Rules: Exploratory Play, Rational Action, and Efficient Search

Recent studies suggest children's exploratory play is consistent with formal accounts of rational learning. Here we focus on the tension between this view and a nearly ubiquitous feature of human play: In play, people subvert normal utility functions, incurring seemingly unnecessary costs to achieve arbitrary rewards. We show that four-and-five-year-old children not only infer playful behavior from observed violations of rational action (Experiment 1), but themselves take on unnecessary costs during both retrieval (Experiment 2) and search (Experiments 3A-B) tasks, despite acting efficiently in non-playful, instrumental contexts. We discuss the value of such apparently utility-violating behavior and why it might serve learning in the long run.

Event-related potential and behavioural evidence of goal-based expectations for consistent actions among group members

PLACEHOLDER TEXT

ABSTRACT: People expect group members to act consistently. However, because actions are organized hierarchically, incorporating deep-level goals and shallow-level movements, it remains unclear what level of action is expected to be consistent among group members. We determined that these two levels of action representations can be dissociated in object-directed actions and measured the late positive potential (LPP), which indicates expectation. We found that participants identified a new agent's actions more quickly when this agent pursued a consistent goal while moving in a manner inconsistent with group members than when this agent pursued an inconsistent goal while moving in the same manner as group members. Moreover, this facilitation effect disappeared when the new agent was from a different group, revealing goal-based expectations for consistent actions among group members. The LPP amplitude during the action-expectation phase was greater for agents from the same group than for agents from a different group, suggesting that people implicitly generate clearer action expectations for group members than for other individuals. Additionally, the behavioural facilitation effect was observed when the goal of actions was clearly identifiable (i.e. performing rational actions to reach an external target) rather than when there was no clear association between actions and external targets (i.e. performing irrational actions). The LPP amplitude during the action-expectation phase was greater after observing rational actions than after observing irrational actions performed by two agents from the same group, and the expectation-related increase in LPP predicted the behavioural measurements of the facilitation effect. Hence, the behavioural and event-related potential evidence suggest that people implicitly expect group members to behave consistently according to goals rather than movements per se.

Commonsense psychology in human infants and machines

Human infants are fascinated by other people. They bring to this fascination a constellation of rich and flexible expectations about the intentions motivating people's actions. Here we test 11-month-old infants and state-of-the-art learning-driven neural-network models on the "Baby Intuitions Benchmark (BIB)," a suite of tasks challenging both infants and machines to make high-level predictions about the underlying causes of agents' actions. Infants expected agents' actions to be directed towards objects, not locations, and infants demonstrated default expectations about agents' rationally efficient actions towards goals. The neural-network models failed to capture infants' knowledge. Our work provides a comprehensive framework in which to characterize infants' commonsense psychology and takes the first step in testing whether human knowledge and human-like artificial intelligence can be built from the foundations cognitive and developmental theories postulate.

People infer communicative action through an expectation for efficient communication

Humans often communicate using body movements like winks, waves, and nods. However, it is unclear how we identify when someone’s physical actions are communicative. Given people’s propensity to interpret each other’s behavior as aimed to produce changes in the world, we hypothesize that people expect communicative actions to efficiently reveal that they lack an external goal. Using computational models of goal inference, we predict that movements that are unlikely to be produced when acting towards the world and, in particular, repetitive ought to be seen as communicative. We find support for our account across a variety of paradigms, including graded acceptability tasks, forced-choice tasks, indirect prompts, and open-ended explanation tasks, in both market-integrated and non-market-integrated communities. Our work shows that the recognition of communicative action is grounded in an inferential process that stems from fundamental computations shared across different forms of action interpretation.

Humans can quickly infer when someone’s body movements are meant to be communicative. Here, the authors show that this capacity is underpinned by an expectation that communicative actions will efficiently reveal that they lack an external goal.

Intelligent wearable allows out-of-the-lab tracking of developing motor abilities in infants

Background

Early neurodevelopmental care needs better, effective and objective solutions for assessing infants' motor abilities. Novel wearable technology opens possibilities for characterizing spontaneous movement behavior. This work seeks to construct and validate a generalizable, scalable, and effective method to measure infants' spontaneous motor abilities across all motor milestones from lying supine to fluent walking.

Methods

A multi-sensor infant wearable was constructed, and 59 infants (age 5-19 months) were recorded during their spontaneous play. A novel gross motor description scheme was used for human visual classification of postures and movements at a second-level time resolution. A deep learning -based classifier was then trained to mimic human annotations, and aggregated recording-level outputs were used to provide posture- and movement-specific developmental trajectories, which enabled more holistic assessments of motor maturity.

Results

Recordings were technically successful in all infants, and the algorithmic analysis showed human-equivalent-level accuracy in quantifying the observed postures and movements. The aggregated recordings were used to train an algorithm for predicting a novel neurodevelopmental measure, Baba Infant Motor Score (BIMS). This index estimates maturity of infants' motor abilities, and it correlates very strongly (Pearson's r = 0.89, p < 1e-20) to the chronological age of the infant.

Conclusions

The results show that out-of-hospital assessment of infants' motor ability is possible using a multi-sensor wearable. The algorithmic analysis provides metrics of motility that are transparent, objective, intuitively interpretable, and they link strongly to infants' age. Such a solution could be automated and scaled to a global extent, holding promise for functional benchmarking in individualized patient care or early intervention trials.

Adopted Utility Calculus: Origins of a Concept of Social Affiliation

To successfully navigate their social world, humans need to understand and map enduring relationships between people: Humans need a concept of social affiliation. Here I propose that the initial concept of social affiliation, available in infancy, is based on the extent to which one individual consistently takes on the goals and needs of another. This proposal grounds affiliation in intuitive psychology, as formalized in the naive-utility-calculus model. A concept of affiliation based on interpersonal utility adoption can account for findings from studies of infants' reasoning about imitation, similarity, helpful and fair individuals, "ritual" behaviors, and social groups without the need for additional innate mechanisms such as a coalitional psychology, moral sense, or general preference for similar others. I identify further tests of this proposal and also discuss how it is likely to be relevant to social reasoning and learning across the life span.

Behavioral and neural representations en route to intuitive action understanding

When we observe another person's actions, we process many kinds of information - from how their body moves to the intention behind their movements. What kinds of information underlie our intuitive understanding about how similar actions are to each other? To address this question, we measured the intuitive similarities among a large set of everyday action videos using multi-arrangement experiments, then used a modeling approach to predict this intuitive similarity space along three hypothesized properties. We found that similarity in the actors' inferred goals predicted the intuitive similarity judgments the best, followed by similarity in the actors' movements, with little contribution from the videos' visual appearance. In opportunistic fMRI analyses assessing brain-behavior correlations, we found suggestive evidence for an action processing hierarchy, in which these three kinds of action similarities are reflected in the structure of brain responses along a posterior-to-anterior gradient on the lateral surface of the visual cortex. Altogether, this work joins existing literature suggesting that humans are naturally tuned to process others' intentions, and that the visuo-motor cortex computes the perceptual precursors of the higher-level representations over which intuitive action perception operates.

Ritualization increases the perceived efficacy of instrumental actions

Across all cultures, people frequently engage in ritualized (non-instrumental) behaviors. How do those causally opaque actions affect perceptions of causal efficacy? Using real-life stimuli extracted from NCAA basketball games, we asked fans, players of the game, and subjects naive to the game to predict the outcome of free throw attempts. We found that the performance of personal pre-shot rituals increased the perception of shot efficacy irrespective of subjects' level of knowledge of and involvement in the game. Those effects became stronger when the score was less favorable for the shooter's team. Our findings suggest that even in non-religious contexts, people make intuitive judgements about ritual efficacy, and that those judgements are sensitive to ecological factors. The implications of those biases extend beyond sports, to various domains of public action, such as religion, courtrooms, college life, and political events.

Action Generalization Across Group Members: Action Efficiency Matters

Actions are usually generalized among social group members. Importantly, the efficiency of an action with respect to achieving an external target determines action understanding, and it may have different degrees of social relevance to social groups. Thus, this study explored the role of action efficiency in action generalization. We used computer animations to simulate actions in social groups initiated by visual action cues or category labels, and we measured differences in response times between identifying actions that were and were not consistent with group members, without explicit requirements regarding generalization. It was found that in both visually introduced and explicitly labeled social groups, when the group members acted inefficiently toward the external object, perceivers identified group-consistent actions faster than group-inconsistent actions, indicating that the exemplars' common inefficient actions are generalized to the unknown ingroup member, accordingly facilitating the identification of expected consistent inefficient action (Experiment 1). As this effect was not present when removing social group cues, it was determined to be specific to social groups (Experiment 2). Importantly, such generalization was not observed when the identical action was deemed efficient toward the external object (Experiment 3) and was specific to the demonstration of the action being completed by multiple group members rather than being repeated twice by one group member, supporting the group-based inference and ruling out the possibility of the increased memorability of inefficient actions leading to more generalization relative to efficient actions (Experiment 4). Therefore, the efficiency of an action bounds the generalization of the action across social group members through a process that is spontaneous and implicit. This constrained action generalization may be due to inefficient actions being represented as culture-specific conventional forms.

Learning From Gesture and Action: An Investigation of Memory for Where Objects Went and How They Got There

Speakers often use gesture to demonstrate how to perform actions-for example, they might show how to open the top of a jar by making a twisting motion above the jar. Yet it is unclear whether listeners learn as much from seeing such gestures as they learn from seeing actions that physically change the position of objects (i.e., actually opening the jar). Here, we examined participants' implicit and explicit understanding about a series of movements that demonstrated how to move a set of objects. The movements were either shown with actions that physically relocated each object or with gestures that represented the relocation without touching the objects. Further, the end location that was indicated for each object covaried with whether the object was grasped with one or two hands. We found that memory for the end location of each object was better after seeing the physical relocation of the objects, that is, after seeing action, than after seeing gesture, regardless of whether speech was absent (Experiment 1) or present (Experiment 2). However, gesture and action built similar implicit understanding of how a particular handgrasp corresponded with a particular end location. Although gestures miss the benefit of showing the end state of objects that have been acted upon, the data show that gestures are as good as action in building knowledge of how to perform an action.

Spontaneity and diversity of movement to music are not uniquely human

Spontaneous movement to music occurs in every human culture and is a foundation of dance [1]. This response to music is absent in most species (including monkeys), yet it occurs in parrots, perhaps because they (like humans, and unlike monkeys) are vocal learners whose brains contain strong auditory-motor connections, conferring sophisticated audiomotor processing abilities [2,3]. Previous research has shown that parrots can bob their heads or lift their feet in synchrony with a musical beat [2,3], but humans move to music using a wide variety of movements and body parts. Is this also true of parrots? If so, it would constrain theories of how movement to music is controlled by parrot brains. Specifically, as head bobbing is part of parrot courtship displays [4] and foot lifting is part of locomotion, these may be innate movements controlled by central pattern generators which become entrained by auditory rhythms, without the involvement of complex motor planning. This would be unlike humans, where movement to music engages cortical networks including frontal and parietal areas [5]. Rich diversity in parrot movement to music would suggest a strong contribution of forebrain regions to this behavior, perhaps including motor learning regions abutting the complex vocal-learning 'shell' regions that are unique to parrots among vocal learning birds [6]. Here we report that a sulphur-crested cockatoo (Cacatua galerita eleonora) responds to music with remarkably diverse spontaneous movements employing a variety of body parts, and suggest why parrots share this response with humans.

The role of context in "over-imitation": Evidence of movement-based goal inference in young children

Children, as well as adults, often imitate causally unnecessary actions. Three experiments investigated whether such "over-imitation" occurs because these actions are interpreted as performed for the movement's sake (i.e., having a "movement-based" goal). Experiment 1 (N = 30, 2-5-year-olds) replicated previous findings; children imitated actions with no goal more precisely than actions with external goals. Experiment 2 (N = 58, 2-5-year-olds) confirmed that the difference between these conditions was not due to the absence/presence of external goals but rather was also found when actions brought about external goals in a clearly inefficient way. Experiment 3 (N = 36, 3-5-year-olds) controlled for the possibility that imitation fidelity was affected by the number of actions and objects present during the demonstration and confirmed that identical actions were imitated more precisely when they appeared to be more inefficient toward an external goal. Our findings suggest that movement-based goal inference encourages over-imitation.

Steps Toward a Universal Grammar of Dance: Local Grouping Structure in Basic Human Movement Perception

The general goal of this paper is to investigate the structure of our unconscious mental representation of dance: we do not perceive dance as an unanalyzed flow of movement, but we unconsciously create a mental representation regulated by structural principles. Specifically, this article examines local grouping principles in dance perception inspired by Lerdahl and Jackendoff's (1983) approach to musical grouping. I spell out the basic perceptual dimensions at work in basic human movement perception, and on that basis, I propose six principles of change that determine group boundaries in dance (change of body part, orientation, level, direction, speed, quality). I experimentally test the relevance and interaction of these principles, and find that they are organized on a scale of relative strength. This experiment thus supports the hypothesis that grouping is a general cognitive capacity applying across domains and modalities, and shows how specific grouping principles are stated in relation to modality-specific and domain-specific dimensions. More generally, it takes a step toward the development of a generative theory of dance that should help extend the research avenue of comparing complex temporal cognitive activities across modalities (visual, auditory) and purposes (referential, non-referential), which so far involves spoken language, signed language and music.

Watching or Listening: How Visual and Verbal Information Contribute to Learning a Complex Dance Phrase

While learning from observation is generally regarded as major learning mode for motor actions, evidence from dance practice suggests that learning dance movement through verbal instruction might provide a promising way to support dancers' individual interpretation of and identification with the movement material. In this multidisciplinary project, we conducted a study on the learning of dance movement through two modalities, observation of a human model in a video clip and listening to the audio-recording of a verbal movement instruction. Eighteen second year dance students learned two dance phrases, one from observation and one from verbal instruction, and were video-recorded performing the learned material. In a second learning step, they were presented the complementary information from the other modality, and their performance was recorded again. A third recording was carried out in a retention test 10 days after learning. Completeness scores representing the recall of the dance phrases, expert ratings addressing the performance quality and questionnaires reflecting the participants' personal impressions were used to evaluate and compare the performance at different stages of the learning process. Results show that learning from observation resulted in better learning outcomes in terms of both recall and approximation of the model phrase, whereas individual interpretation of the learned movement material was rated equally good after initially verbal and initially visual learning. According to the questionnaires, most participants preferred learning initially from observation and found it more familiar, which points toward an influence of learning habit caused by common training practice. The findings suggest that learning dance movement initially from observation is more beneficial than from verbal instruction, and add aspects with regards to multimodal movement learning with potential relevance for dance teaching and training.

My Action, My Self: Recognition of Self-Created but Visually Unfamiliar Dance-Like Actions From Point-Light Displays

Previous research has shown that motor experience of an action can facilitate the visual recognition of that action, even in the absence of visual experience. We conducted an experiment in which participants were presented point-light displays of dance-like actions that had been recorded with the same group of participants during a previous session. The stimuli had been produced with the participant in such a way that each participant experienced a subset of phrases only as observer, learnt two phrases from observation, and created one phrase while blindfolded. The clips presented in the recognition task showed movements that were either unfamiliar, only visually familiar, familiar from observational learning and execution, or self-created while blind-folded (and hence not visually familiar). Participants assigned all types of movements correctly to the respective categories, showing that all three ways of experiencing the movement (observed, learnt through observation and practice, and created blindfolded) resulted in an encoding that was adequate for recognition. Observed movements showed the lowest level of recognition accuracy, whereas the accuracy of assigning blindfolded self-created movements was on the same level as for unfamiliar and learnt movements. Self-recognition was modulated by action recognition, as participants were more likely to identify themselves as the actor in clips they had assigned to the category "created" than in clips they had assigned to the category "learnt," supporting the idea of an influence of agency on self-recognition.

The Rationality of (Over)imitation

Imitation is a powerful and ubiquitous social learning strategy, fundamental for the development of individual skills and cultural traditions. Recent research on the cognitive foundations and development of imitation, though, presents a surprising picture: Although even infants imitate in selective, efficient, and rational ways, children and adults engage in overimitation. Rather than imitating selectively and efficiently, they sometimes faithfully reproduce causally irrelevant actions as much as relevant ones. In this article, we suggest a new perspective on this phenomenon by integrating established findings on children’s more general capacities for rational action parsing with newer findings on overimitation. We suggest that overimitation is a consequence of children’s growing capacities to understand causal and social constraints in relation to goals and that it rests on the human capacity to represent observed actions simultaneously on different levels of goal hierarchies.

Sensitivity to the Sampling Process Emerges From the Principle of Efficiency

Humans can seamlessly infer other people's preferences, based on what they do. Broadly, two types of accounts have been proposed to explain different aspects of this ability. The first account focuses on spatial information: Agents' efficient navigation in space reveals what they like. The second account focuses on statistical information: Uncommon choices reveal stronger preferences. Together, these two lines of research suggest that we have two distinct capacities for inferring preferences. Here we propose that this is not the case, and that spatial-based and statistical-based preference inferences can be explained by the assumption that agents are efficient alone. We show that people's sensitivity to spatial and statistical information when they infer preferences is best predicted by a computational model of the principle of efficiency, and that this model outperforms dual-system models, even when the latter are fit to participant judgments. Our results suggest that, as adults, a unified understanding of agency under the principle of efficiency underlies our ability to infer preferences.

Human infants' understanding of social imitation: Inferences of affiliation from third party observations

Imitation is ubiquitous in positive social interactions. For adult and child observers, it also supports inferences about the participants in such interactions and their social relationships, but the origins of these inferences are obscure. Do infants attach social significance to this form of interaction? Here we test 4- to 5.5-month-old infants' interpretation of imitation, asking if the imitative interactions they observe support inferences of social affiliation, across 10 experimental conditions that varied the modality of the imitation (movement vs. sound), the roles of specific characters (imitators vs. targets), the number of characters in the displays (3 vs. 5), and the number of parties initiating affiliative test events (1 vs. 2). These experiments, together with one experiment conducted with 12-month-old infants, yielded three main findings. First, infants expect that characters who engaged in imitation will approach and affiliate with the characters whom they imitated. Second, infants show no evidence of expecting that characters who were targets of imitation will approach and affiliate with their imitators. Third, analyzing imitative interactions is difficult for young infants, whose expectations vary in strength depending on the number of characters to be tracked and the number of affiliative actors to be compared. These findings have implications for our understanding of social imitation, and they provide methods for advancing understanding of other aspects of early social cognitive development.

Control blindness: Why people can make incorrect inferences about the intentions of others

There is limited evidence regarding the accuracy of inferences about intention. The research described in this article shows how perceptual control theory (PCT) can provide a “ground truth” for these judgments. In a series of 3 studies, participants were asked to identify a person’s intention in a tracking task where the person’s true intention was to control the position of a knot connecting a pair of rubber bands. Most participants failed to correctly infer the person’s intention, instead inferring complex but nonexistent goals (such as “tracing out two kangaroos boxing”) based on the actions taken to keep the knot under control. Therefore, most of our participants experienced what we call “control blindness.” The effect persisted with many participants even when their awareness was successfully directed at the knot whose position was under control. Beyond exploring the control blindness phenomenon in the context of our studies, we discuss its implications for psychological research and public policy.

Gesture as representational action: A paper about function

A great deal of attention has recently been paid to gesture and its effects on thinking and learning. It is well established that the hand movements that accompany speech are an integral part of communication, ubiquitous across cultures, and a unique feature of human behavior. In an attempt to understand this intriguing phenomenon, researchers have focused on pinpointing the mechanisms that underlie gesture production. One proposal--that gesture arises from simulated action (Hostetter & Alibali Psychonomic Bulletin & Review, 15, 495-514, 2008)--has opened up discussions about action, gesture, and the relation between the two. However, there is another side to understanding a phenomenon and that is to understand its function. A phenomenon's function is its purpose rather than its precipitating cause--the why rather than the how. This paper sets forth a theoretical framework for exploring why gesture serves the functions that it does, and reviews where the current literature fits, and fails to fit, this proposal. Our framework proposes that whether or not gesture is simulated action in terms of its mechanism--it is clearly not reducible to action in terms of its function. Most notably, because gestures are abstracted representations and are not actions tied to particular events and objects, they can play a powerful role in thinking and learning beyond the particular, specifically, in supporting generalization and transfer of knowledge.

Unpacking the Ontogeny of Gesture Understanding: How Movement Becomes Meaningful Across Development

Gestures, hand movements that accompany speech, affect children's learning, memory, and thinking (e.g., Goldin-Meadow, 2003). However, it remains unknown how children distinguish gestures from other kinds of actions. In this study, 4- to 9-year-olds (n = 339) and adults (n = 50) described one of three scenes: (a) an actor moving objects, (b) an actor moving her hands in the presence of objects (but not touching them), or (c) an actor moving her hands in the absence of objects. Participants across all ages were equally able to identify actions on objects as goal directed, but the ability to identify empty-handed movements as representational actions (i.e., as gestures) increased with age and was influenced by the presence of objects, especially in older children.

Parents scaffold flexible imitation during early childhood

Children use imitation flexibly to acquire the instrumental skills and conventions of their social groups. This study (N=69 parent and 3- to 6-year-old child dyads) examined the impact of instrumental versus conventional language on (a) children's imitative flexibility in the context of parent-child interaction and (b) how parents scaffold children's imitation. Children in dyads presented with conventional language imitated with higher fidelity than children in dyads presented with instrumental language. Parents in dyads presented with conventional language also provided their children with more instruction to imitate and engaged in more encouragement, demonstration, and monitoring than parents in dyads presented with instrumental language. The relation between language cue and children's imitative fidelity was mediated by parent scaffolding behavior. The results provide evidence that caregivers support the development of flexible imitation during early childhood by adjusting their scaffolding according to the goal of the behavior.

What makes a movement a gesture?

Theories of how adults interpret the actions of others have focused on the goals and intentions of actors engaged in object-directed actions. Recent research has challenged this assumption, and shown that movements are often interpreted as being for their own sake (Schachner & Carey, 2013). Here we postulate a third interpretation of movement-movement that represents action, but does not literally act on objects in the world. These movements are gestures. In this paper, we describe a framework for predicting when movements are likely to be seen as representations. In Study 1, adults described one of three scenes: (1) an actor moving objects, (2) an actor moving her hands in the presence of objects (but not touching them) or (3) an actor moving her hands in the absence of objects. Participants systematically described the movements as depicting an object-directed action when the actor moved objects, and favored describing the movements as depicting movement for its own sake when the actor produced the same movements in the absence of objects. However, participants favored describing the movements as representations when the actor produced the movements near, but not on, the objects. Study 2 explored two additional features-the form of an actor's hands and the presence of speech-like sounds-to test the effect of context on observers' classification of movement as representational. When movements are seen as representations, they have the power to influence communication, learning, and cognition in ways that movement for its own sake does not. By incorporating representational gesture into our framework for movement analysis, we take an important step towards developing a more cohesive understanding of action-interpretation.

Learning from gesture: How early does it happen?

Iconic gesture is a rich source of information for conveying ideas to learners. However, in order to learn from iconic gesture, a learner must be able to interpret its iconic form-a nontrivial task for young children. Our study explores how young children interpret iconic gesture and whether they can use it to infer a previously unknown action. In Study 1, 2- and 3-year-old children were shown iconic gestures that illustrated how to operate a novel toy to achieve a target action. Children in both age groups successfully figured out the target action more often after seeing an iconic gesture demonstration than after seeing no demonstration. However, the 2-year-olds (but not the 3-year-olds) figured out fewer target actions after seeing an iconic gesture demonstration than after seeing a demonstration of an incomplete-action and, in this sense, were not yet experts at interpreting gesture. Nevertheless, both age groups seemed to understand that gesture could convey information that can be used to guide their own actions, and that gesture is thus not movement for its own sake. That is, the children in both groups produced the action displayed in gesture on the object itself, rather than producing the action in the air (in other words, they rarely imitated the experimenter's gesture as it was performed). Study 2 compared 2-year-olds' performance following iconic vs. point gesture demonstrations. Iconic gestures led children to discover more target actions than point gestures, suggesting that iconic gesture does more than just focus a learner's attention, it conveys substantive information about how to solve the problem, information that is accessible to children as young as 2. The ability to learn from iconic gesture is thus in place by toddlerhood and, although still fragile, allows children to process gesture, not as meaningless movement, but as an intentional communicative representation.

Perceptions of intentionality for goal-related action: behavioral description matters

Perceptions of intentionality critically guide everyday social interactions, though the literature provides diverging portraits of how such judgments are made. One view suggests that people have an "intentionality bias," predisposing them toward labeling behaviors as intentional. A second view focuses on a more complex pattern of reasoning whereby judgments of intentionality are shaped by information about social context and mental states. Drawing on the theory of action-identification, we attempt to integrate these two perspectives. We propose that people parse intentionality into two categories: judgments about concrete, low-level behaviors and judgments about relatively more abstract, high-level behaviors. Evidence from five studies supports this distinction. Low-level behaviors were perceived as intentional regardless of mental state information, supporting the "intentionality bias" view. In contrast, judgments about the intentionality of high-level behaviors varied depending on social context and mental states, supporting the systematic view of intentionality.

Segmentation of dance movement: effects of expertise, visual familiarity, motor experience and music

According to event segmentation theory, action perception depends on sensory cues and prior knowledge, and the segmentation of observed actions is crucial for understanding and memorizing these actions. While most activities in everyday life are characterized by external goals and interaction with objects or persons, this does not necessarily apply to dance-like actions. We investigated to what extent visual familiarity of the observed movement and accompanying music influence the segmentation of a dance phrase in dancers of different skill level and non-dancers. In Experiment 1, dancers and non-dancers repeatedly watched a video clip showing a dancer performing a choreographed dance phrase and indicated segment boundaries by key press. Dancers generally defined less segment boundaries than non-dancers, specifically in the first trials in which visual familiarity with the phrase was low. Music increased the number of segment boundaries in the non-dancers and decreased it in the dancers. The results suggest that dance expertise reduces the number of perceived segment boundaries in an observed dance phrase, and that the ways visual familiarity and music affect movement segmentation are modulated by dance expertise. In a second experiment, motor experience was added as factor, based on empirical evidence suggesting that action perception is modified by visual and motor expertise in different ways. In Experiment 2, the same task as in Experiment 1 was performed by dance amateurs, and was repeated by the same participants after they had learned to dance the presented dance phrase. Less segment boundaries were defined in the middle trials after participants had learned to dance the phrase, and music reduced the number of segment boundaries before learning. The results suggest that specific motor experience of the observed movement influences its perception and anticipation and makes segmentation broader, but not to the same degree as dance expertise on a professional level.