Neurocognitive mechanisms underlying social learning in infancy: infants' neural processing of the effects of others' actions

Visual attention for linguistic and non-linguistic body actions in non-signing and native signing children

Evidence from adult studies of deaf signers supports the dissociation between neural systems involved in processing visual linguistic and non-linguistic body actions. The question of how and when this specialization arises is poorly understood. Visual attention to these forms is likely to change with age and be affected by prior language experience. The present study used eye-tracking methodology with infants and children as they freely viewed alternating video sequences of lexical American sign language (ASL) signs and non-linguistic body actions (self-directed grooming action and object-directed pantomime). In Experiment 1, we quantified fixation patterns using an area of interest (AOI) approach and calculated face preference index (FPI) values to assess the developmental differences between 6 and 11-month-old hearing infants. Both groups were from monolingual English-speaking homes with no prior exposure to sign language. Six-month-olds attended the signer's face for grooming; but for mimes and signs, they were drawn to attend to the "articulatory space" where the hands and arms primarily fall. Eleven-month-olds, on the other hand, showed a similar attention to the face for all body action types. We interpret this to reflect an early visual language sensitivity that diminishes with age, just before the child's first birthday. In Experiment 2, we contrasted 18 hearing monolingual English-speaking children (mean age of 4.8 years) vs. 13 hearing children of deaf adults (CODAs; mean age of 5.7 years) whose primary language at home was ASL. Native signing children had a significantly greater face attentional bias than non-signing children for ASL signs, but not for grooming and mimes. The differences in the visual attention patterns that are contingent on age (in infants) and language experience (in children) may be related to both linguistic specialization over time and the emerging awareness of communicative gestural acts.

Social context shapes neural processing of others' actions in 9-month-old infants

From infancy, neural processes for perceiving others' actions and producing one's own actions overlap (neural mirroring). Adults and children show enhanced mirroring in social interactions. Yet, whether social context affects mirroring in infancy, a time when processing others' actions is crucial for action learning, remains unclear. We examined whether turn-taking, an early form of social interaction, enhanced 9-month-olds' neural mirroring. We recorded electroencephalography while 9-month-olds were grasping (execution) and observing live grasps (observation). In this design, half of the infants observed and acted in alternation (turn-taking condition), whereas the other half observed several times in a row before acting (blocked condition). Replicating previous findings, infants showed significant 6- to 9-Hz mu suppression (indicating motor activation) during execution and observation (n = 24). In addition, a condition (turn-taking or blocked) by time (action start or end) interaction indicated that infants engaged in turn-taking (n = 9), but not in the blocked context (n = 15), showed more mirroring when observing the action start compared with the action end. Exploratory analyses further suggest that (a) there is higher visual-motor functional connectivity in turn-taking toward the action's end, (b) mirroring relates to later visual-motor connectivity, and (c) visual attention as indexed by occipital alpha is enhanced in turn-taking compared with the blocked context. Together, this suggests that the neural processing of others' actions is modulated by the social context in infancy and that turn-taking may be particularly effective in engaging infants' action perception system.

Social learning of action-effect associations: Modulation of action control following observation of virtual action's effects

A core assumption of ideomotor theory is that learned bidirectional associations between actions and their effects enable agents to select and initiate actions by anticipating their sensory consequences. Although the acquisition of bidirectional action-effect (A-E) associations built on the experience of one's own movements has received considerable empirical support, the available evidence for A-E learning through the observation of others' actions and their effects remains limited. In two experiments, we tested whether A-E associations could be acquired through social learning in an experimental setup involving observation of virtual actions. In an acquisition phase, participants repeatedly observed finger movements on a screen, and each movement was consistently followed by a specific effect tone. In the subsequent test phase, tones were presented as imperative stimuli in a reaction-time task. In both experiments, reaction times were shorter when tones required the same response with which they had been linked in the preceding observation phase, compared with when they required a different response, revealing the impact of A-E associations acquired through observation. Similar results were obtained whether the movements observed during the acquisition phase were spatially aligned (Experiment 1) or not (Experiment 2) with participants' responses in the test phase, ruling out the possibility that the results merely reflect spatial compatibility effects. Our findings add new evidence for an acquisition of A-E associations through observation. Importantly, we generalize this acquisition process to the observation of virtual actions. These findings further confirm effect-based action control, as proposed by ideomotor theory.

Traces of culture: The feedback loop between behavior, brain, and disorder

Culture is part of an extensive series of feedback loops, which involve multiple organismic levels including social contexts, cognitive mediations, neural processes, and behavior. Recent studies in neuroscience show that culturally contingent social processes shape some neural pathways. Studying the influence of cultural context on neural processes may yield new insights into psychiatric disorders. New methodologies in the neurosciences offer innovative ways to assess the impact of culture on mental health and illness. However, implementing these methodologies raises important theoretical and ethical concerns, which must be resolved to address patient individuality and the complexity of cultural diversity. This article discusses cultural context as a major influence on (and consequence of) human neural plasticity and advocates a culture-brain-behavior (CBB) interaction model for conceptualizing the relationship between culture, brain, and psychiatric disorders. Recommendations are made for integrating neuroscientific techniques into transcultural psychiatric research by taking a systems approach to evaluating disorders.

Training of 7-month-old infants' manual object exploration skills: Effects of active and observational experience

In the present study, a fine motor training was developed and evaluated in which infants were trained to manually explore objects in an advanced manner. Fifty 7-month-old infants were randomly assigned to three different training conditions: (1) to an active manual exploration training, in which they learned to explore objects efficiently, (2) to an observational manual exploration training, in which they observed how an adult performed sophisticated actions on objects, or (3) to a control group receiving no training. The results impressively indicate that infants with a low level of object exploration skill prior to the training showed the most training effects as compared to infants with proficient object exploratory actions. Interestingly, this differential training effect was true for both the active and observational training, highlighting the role of social learning in infancy. Importantly, our study shows for the first time the impact of normal individual variation in infants' manual object exploration skills on the effects of a fine motor training.

Effects of active and observational experience on EEG activity during early childhood

While it is accepted that action experience facilitates action understanding, it is debated whether first-hand motor and visual experience differentially influence this ability. Action understanding relies on relatively broad cortical activity, including that of the neural mirroring and visual attention systems. Infant and adult research has demonstrated that prior motor and visual experience have distinct effects on cortical activity during action perception, though this has yet to be investigated in young children. We used a within-subject design and an at-home training paradigm to manipulate 3- to 6-year-olds' experience with two relatively novel actions. On Days 1-4, children received brief active training with one tool (i.e., motor experience) and observational training with the other tool (i.e., visual experience: video of a demonstrator modeling the action). On Day 5, we measured children's EEG mu/alpha (8-10 Hz) and beta rhythm (16-20 Hz) activity during observation and execution of these actions in the laboratory. Although central-parietal mu and beta rhythm activity did not differ as a function of training condition, desynchronization of the occipital alpha rhythm was greater during perception of the active training task than of the observational training task. Our findings suggest that, during early childhood, action experience may modulate visual attention during subsequent action perception. Further, children exhibited neural mirroring-central-parietal desynchronization during both tool-use action observation and execution-within the mu rhythm, but not the beta rhythm. These findings have significant implications for our understanding of the broad cortical activity that supports action perception during this period.

Intergenerational transmission of traumatization: Theoretical framework and implications for prevention

Intergenerational transmission of traumatization (ITT) occurs when traumatized parents have offspring with increased risk for emotional and behavioral problems. Although fetal exposure to the maternal biological milieu is known to be one factor in ITT, PTSD-driven parent-child interactions represent an additional important and potentially modifiable contributor. The Perinatal Interactional Model of ITT presented herein proposes that PTSD leads to social learning and suboptimal parent-child interactions, which undermine child regulatory capacity and increase distress, largely explaining poor social-emotional outcomes for offspring of parents with PTSD. Psychosocial intervention, particularly when delivered early in pregnancy, holds the possibility of disrupting ITT.

Independent Development of Imagination and Perception of Fitts' Law in Late Childhood and Adolescence

Recent neurophysiological and behavioral research suggests perception-action systems are tightly coupled. Accordingly, Fitts' law has been observed when individuals execute, perceive, and imagine actions. Developmental research has found that (a) children demonstrate Fitts' law in imagined actions and (b) imagined movement time (MT) becomes closer to actual MT as age increases. However, action execution, imagination, and perception have yet to be assessed together in children. The authors investigated how imagined and perceived MTs related to actual MTs in children and adolescents. It was found that imagined MTs were longer than execution MTs were. Perception MTs were lower than execution MTs for children and more consistent with execution MTs for adolescents. These results suggest potential mechanistic differences in action imagination and perception.

Infants' Understanding of Object-Directed Action: An Interdisciplinary Synthesis

Recognizing that the object-directed actions of others are governed by goals and intentions is a crucial component of human interaction. These actions often occur rapidly and without explanation, yet we learn from and predict the actions of others with remarkable speed and accuracy, even during the first year of life. This review paper will serve as a bridge between several disparate literatures that, we suggest, can each contribute to our understanding of how infants interpret action. Specifically, we provide a review not just of research on infant goal attribution per se, but also incorporate findings from studies on the mirror neuron system and infant object cognition. The integration of these various research approaches allows for a novel construal of the extents and limits of early goal attribution – one in which the importance of the entire action context is considered – and points to specific future research directions.

Clarifying the range of social-cognitive processes subserving human teaching

An evolutionary framework on human teaching is not well equipped to explain the nature of human teaching unless it specifies the subserving cognitive and motivational mechanisms. Only a theory that speculates on the psychological processes provides testable predictions and stimulates further empirical research.

Short-term Motor Training, but Not Observational Training, Alters Neurocognitive Mechanisms of Action Processing in Infancy

The role of motor experience in the processing of perceived actions is hotly debated on both behavioral (e.g., action understanding) and neural (e.g., activation of the motor system) levels of interpretation. Whereas some researchers focus on the role of motor experience in the understanding of and motor activity associated with perceived actions, others emphasize the role of visual experience with the perceived actions. The question of whether prior firsthand motor experience is critical to motor system activation during perception of actions performed by others is best addressed through studies with infants who have a limited repertoire of motor actions. In this way, infants can receive motor or visual training with novel actions that are not mere recombinations of previously acquired actions. In this study, 10-month-old infants received active training with a motorically unfamiliar action that resulted in a distinct sound effect. They received observational experience with a second, similarly unfamiliar action. Following training, we assessed infants' neural motor activity via EEG while they listened to the sounds associated with the actions relative to a novel sound. We found a greater decrease in mu power to sounds associated with the motorically learned action than to those associated with the observed action that the infants had never produced. This effect was directly related to individual differences in the degree of motor learning via motor training. These findings indicate a unique effect of active experience on neural correlates of action perception.

Infant frontal asymmetry predicts child emotional availability

While factors influencing maternal emotional availability (EA) have been well investigated, little is known about the development of child EA. The present longitudinal study investigated the role of frontal brain asymmetry in young children with regard to child EA (child responsiveness and involvement) in mother–child interaction in a sample of 28 children at 7, 14, and 50 months of age. When infants were 7 months of age, mother–child interaction quality was assessed using the EA-Scales. At 14 months, infants’ resting asymmetric frontal activity was assessed by means of the electroencephalogram (EEG). When children were 50 months old, mother–child interaction quality was measured again. Analyses showed that relatively higher left frontal EEG activation was related to higher child involvement at 50 months, but not to child responsiveness. Those findings suggest a specific relation between individual differences in frontal asymmetry, and child approach and initiating behaviors in mother–child interaction.

What are you doing? How active and observational experience shape infants' action understanding

From early in life, infants watch other people's actions. How do young infants come to make sense of actions they observe? Here, we review empirical findings on the development of action understanding in infancy. Based on this review, we argue that active action experience is crucial for infants' developing action understanding. When infants execute actions, they form associations between motor acts and the sensory consequences of these acts. When infants subsequently observe these actions in others, they can use their motor system to predict the outcome of the ongoing actions. Also, infants come to an understanding of others' actions through the repeated observation of actions and the effects associated with them. In their daily lives, infants have plenty of opportunities to form associations between observed events and learn about statistical regularities of others' behaviours. We argue that based on these two forms of experience-active action experience and observational experience-infants gradually develop more complex action understanding capabilities.

Neural mirroring mechanisms and imitation in human infants

Studying human infants will increase our understanding of the nature, origins and function of neural mirroring mechanisms. Human infants are prolific imitators. Infant imitation indicates observation-execution linkages in the brain prior to language and protracted learning. Investigations of neural aspects of these linkages in human infants have focused on the sensorimotor mu rhythm in the electroencephalogram, which occurs in the alpha frequency range over central electrode sites. Recent results show that the infant mu rhythm is desynchronized during action execution as well as action observation. Current work is elucidating properties of the infant mu rhythm and how it may relate to prelinguistic action processing and social understanding. Here, we consider this neuroscience research in relation to developmental psychological theory, particularly the 'Like-Me' framework, which holds that one of the chief cognitive tasks of the human infant is to map the similarity between self and other. We elucidate the value of integrating neuroscience findings with behavioural studies of infant imitation, and the reciprocal benefit of examining mirroring mechanisms from an ontogenetic perspective.

The Infant EEG Mu Rhythm: Methodological Considerations and Best Practices

The EEG mu rhythm, recorded from scalp regions overlying the sensorimotor cortex, appears to exhibit mirroring properties: It is reactive when performing an action and when observing another perform the same action. Recently, there has been an exponential increase in developmental mu rhythm research, partially due to the mu rhythm's potential role in our understanding of others' actions as well as a variety of other social and cognitive processes (e.g., imitation, theory of mind, language). Unfortunately, various methodological issues impede integrating these findings into a comprehensive theory of mu rhythm development. The present manuscript provides a review of the infant mu rhythm literature while focusing on current methodological problems that impede between study comparisons. By highlighting these issues and providing an in depth description and analysis we aim to heighten awareness and propose guidelines (when possible) that will promote rigorous infant mu rhythm research and facilitate between study comparisons. This paper is intended as a resource for developmental scientists, regardless of EEG expertise.

The joint role of trained, untrained, and observed actions at the origins of goal recognition

Recent findings across a variety of domains reveal the benefits of self-produced experience on object exploration, object knowledge, attention, and action perception. The influence of active experience may be particularly important in infancy, when motor development is undergoing great changes. Despite the importance of self-produced experience, we know that infants and young children are eventually able to gain knowledge through purely observational experience. In the current work, three-month-old infants were given experience with object-directed actions in one of three forms and their recognition of the goal of grasping actions was then assessed in a habituation paradigm. All infants were given the chance to manually interact with the toys without assistance (a difficult task for most three-month-olds). Two of the three groups were then given additional experience with object-directed actions, either through active training (in which Velcro mittens helped infants act more efficiently) or observational training. Findings support the conclusion that self-produced experience is uniquely informative for action perception and suggest that individual differences in spontaneous motor activity may interact with observational experience to inform action perception early in life.

Early rationality in action perception and production? A theoretical exposition

Within recent years, the question of early rationality in action perception and production has become a topic of great interest in developmental psychology. On the one hand, studies have provided evidence for rational action perception and action imitation even in very young infants. On the other hand, scholars have recently questioned these interpretations and proposed that the ability to rationally evaluate actions is not yet in place in infancy. Others have examined the development of the ability to make rational action choices and have indicated limitations of young children's ability to act rationally. This editorial to the special issue on Early Rationality in Action Perception and Production? introduces the reader to the current debate. It elucidates the underlying theoretical assumptions that drive the debate on whether or not young children's action perception and production is rational. Finally, it summarizes the papers and their contributions to the theoretical debate.