Event-related potentials to intact and disrupted actions in children and adults

Reading minds or reading scripts? De-intellectualising theory of mind

Understanding the origins of human social cognition is a central challenge in contemporary science. In recent decades, the idea of a 'Theory of Mind' (ToM) has emerged as the most popular way of explaining unique features of human social cognition. This default view has been progressively undermined by research on 'implicit' ToM, which suggests that relevant precursor abilities may already be present in preverbal human infants and great apes. However, this area of research suffers from conceptual difficulties and empirical limitations, including explanatory circularity, over-intellectualisation, and inconsistent empirical replication. Our article breaks new ground by adapting 'script theory' for application to both linguistic and non-linguistic agents. It thereby provides a new theoretical framework able to resolve the aforementioned issues, generate novel predictions, and provide a plausible account of how individuals make sense of the behaviour of others. Script theory is based on the premise that pre-verbal infants and great apes are capable of basic forms of agency-detection and non-mentalistic goal understanding, allowing individuals to form event-schemata that are then used to make sense of the behaviour of others. We show how script theory circumvents fundamental problems created by ToM-based frameworks, explains patterns of inconsistent replication, and offers important novel predictions regarding how humans and other animals understand and predict the behaviour of others.

Neural event segmentation of continuous experience in human infants

How infants experience the world is fundamental to understanding their cognition and development. A key principle of adult experience is that, despite receiving continuous sensory input, we perceive this input as discrete events. Here we investigate such event segmentation in infants and how it differs from adults. Research on event cognition in infants often uses simplified tasks in which (adult) experimenters help solve the segmentation problem for infants by defining event boundaries or presenting discrete actions/vignettes. This presupposes which events are experienced by infants and leaves open questions about the principles governing infant segmentation. We take a different, data-driven approach by studying infant event segmentation of continuous input. We collected whole-brain functional MRI (fMRI) data from awake infants (and adults, for comparison) watching a cartoon and used a hidden Markov model to identify event states in the brain. We quantified the existence, timescale, and organization of multiple-event representations across brain regions. The adult brain exhibited a known hierarchical gradient of event timescales, from shorter events in early visual regions to longer events in later visual and associative regions. In contrast, the infant brain represented only longer events, even in early visual regions, with no timescale hierarchy. The boundaries defining these infant events only partially overlapped with boundaries defined from adult brain activity and behavioral judgments. These findings suggest that events are organized differently in infants, with longer timescales and more stable neural patterns, even in sensory regions. This may indicate greater temporal integration and reduced temporal precision during dynamic, naturalistic perception.

Kinematic boundary cues modulate 12-month-old infants' segmentation of action sequences: An ERP study

Human infants can segment action sequences into their constituent actions already during the first year of life. However, work to date has almost exclusively examined the role of infants' conceptual knowledge of actions and their outcomes in driving this segmentation. The present study examined electrophysiological correlates of infants' processing of lower-level perceptual cues that signal a boundary between two actions of an action sequence. Specifically, we tested the effect of kinematic boundary cues (pre-boundary lengthening and pause) on 12-month-old infants' (N = 27) processing of a sequence of three arbitrary actions, performed by an animated figure. Using the Event-Related Potential (ERP) approach, evidence of a positivity following the onset of the boundary cues was found, in line with previous work that has found an ERP positivity (Closure Positive Shift, CPS) related to boundary processing in auditory stimuli and action sequences in adults. Moreover, an ERP negativity (Negative Central, Nc) indicated that infants' encoding of the post-boundary action was modulated by the presence or absence of prior boundary cues. We therefore conclude that 12-month-old infants are sensitive to lower-level perceptual kinematic boundary cues, which can support segmentation of a continuous stream of movement into individual action units.

Children's reasoning about the efficiency of others' actions: The development of rational action prediction

The relative efficiency of an action is a central criterion in action control and can be used to predict others' behavior. Yet, it is unclear when the ability to predict on and reason about the efficiency of others' actions develops. In three main and two follow-up studies, 3- to 6-year-old children (n = 242) were confronted with vignettes in which protagonists could take a short (efficient) path or a long path. Children predicted which path the protagonist would take and why the protagonist would take a specific path. The 3-year-olds did not take efficiency into account when making decisions even when there was an explicit goal, the task was simplified and made more salient, and children were questioned after exposure to the agent's action. Four years is a transition age for rational action prediction, and the 5-year-olds reasoned on the efficiency of actions before relying on them to predict others' behavior. Results are discussed within a representational redescription account.

Eighteen-month-olds integrate verbal cues into their action processing: Evidence from ERPs and mu power

Behavioral research has shown that infants use both behavioral cues and verbal cues when processing the goals of others' actions. For instance, 18-month-olds selectively imitate an observed goal-directed action depending on its (in)congruence with a model's previous verbal announcement of a desired action goal. This EEG-study analyzed the electrophysiological underpinnings of these behavioral findings on the two functional levels of conceptual action processing and motor activation. Mid-latency mean negative ERP amplitude and mu-frequency band power were analyzed while 18-month-olds (N = 38) watched videos of an adult who performed one out of two potential actions on a novel object. In a within-subjects design, the action demonstration was preceded by either a congruent or an incongruent verbally announced action goal (e.g., "up" or "down" and upward movement). Overall, ERP negativity did not differ between conditions, but a closer inspection revealed that in two subgroups, about half of the infants showed a broadly distributed increased mid-latency ERP negativity (indicating enhanced conceptual action processing) for either the congruent or the incongruent stimuli, respectively. As expected, mu power at sensorimotor sites was reduced (indicating enhanced motor activation) for congruent relative to incongruent stimuli in the entire sample. Both EEG correlates were related to infants' language skills. Hence, 18-month-olds integrate action-goal-related verbal cues into their processing of others' actions, at the functional levels of both conceptual processing and motor activation. Further, cue integration when inferring others' action goals is related to infants' language proficiency.

The organization of words and environmental sounds in the second year: Behavioral and electrophysiological evidence

The majority of research examining early auditory-semantic processing and organization is based on studies of meaningful relations between words and referents. However, a thorough investigation into the fundamental relation between acoustic signals and meaning requires an understanding of how meaning is associated with both lexical and non-lexical sounds. Indeed, it is unknown how meaningful auditory information that is not lexical (e.g., environmental sounds) is processed and organized in the young brain. To capture the structure of semantic organization for words and environmental sounds, we record event-related potentials as 20-month-olds view images of common nouns (e.g., dog) while hearing words or environmental sounds that match the picture (e.g., "dog" or barking), that are within-category violations (e.g., "cat" or meowing), or that are between-category violations (e.g., "pen" or scribbling). Results show both words and environmental sounds exhibit larger negative amplitudes to between-category violations relative to matches. Unlike words, which show a greater negative response early and consistently to within-category violations, such an effect for environmental sounds occurs late in semantic processing. Thus, as in adults, the young brain represents semantic relations between words and between environmental sounds, though it more readily differentiates semantically similar words compared to environmental sounds.

Meaningful Memory? Eighteen-Month-Olds Only Remember Cartoons With a Meaningful Storyline

In two studies we investigated the importance of a storyline for remembering cartoons across a delay of 2 weeks in 18-month-old infants by means of the visual paired-comparison (VPC) paradigm. In Study 1 seventy-one 18-month-olds were tested using similar cartoons as in a recent study from our lab while varying the richness of the storyline information. In a VPC task half of the infants watched uncompromised versions of the cartoons used in the recent study (Storyline Condition), whereas the other half watched Pixelized versions of the cartoons (number of pixels reduced by 98% covering up the narrative, but leaving perceptual details, e.g., colors, movements, the same, and Pixelized Condition). Two weeks later they were presented with the familiar cartoon and a novel cartoon from the same version (Storyline or Pixelized) simultaneously, while being eye-tracked. Results showed that only the infants in the Storyline Condition remembered the target cartoon, thus suggesting that the storyline is important for memory. However, an alternative interpretation of the results could be that what made the infants in the Storyline Condition remember the target cartoon was not the storyline, but the static conceptual information of the objects and agents present in the cartoon (which was not visible in the Pixelized version). To test this possibility, a control study was created. In Study 2 thirty-six infants were therefore presented with a version of the cartoon in which we broke down the temporal presentation into 1 s segments and presented these out of order. This was done to preserve the static conceptual information (e.g., objects and agents) while still disturbing the storyline. Results showed that the infants in this condition still did not remember the target cartoon, suggesting that the meaningfulness of the storyline - and not only static conceptual information - is important for later memory.

Reduced Mu Power in Response to Unusual Actions Is Context-Dependent in 1-Year-Olds

During social interactions infants predict and evaluate other people's actions. Previous behavioral research found that infants' imitation of others' actions depends on these evaluations and is context-dependent: 1-year-olds predominantly imitated an unusual action (turning on a lamp with one's forehead) when the model's hands were free compared to when the model's hands were occupied or restrained. In the present study, we adapted this behavioral paradigm to a neurophysiological study measuring infants' brain activity while observing usual and unusual actions via electroencephalography. In particular, we measured differences in mu power (6 - 8 Hz) associated with motor activation. In a between-subjects design, 12- to 14-month-old infants watched videos of adult models demonstrating that their hands were either free or restrained. Subsequent test frames showed the models turning on a lamp or a soundbox by using their head or their hand. Results in the hands-free condition revealed that 12- to 14-month-olds displayed a reduction of mu power in frontal regions in response to unusual and thus unexpected actions (head touch) compared to usual and expected actions (hand touch). This may be explained by increased motor activation required for updating prior action predictions in response to unusual actions though alternative explanations in terms of general attention or cognitive control processes may also be considered. In the hands-restrained condition, responses in mu frequency band did not differ between action outcomes. This implies that unusual head-touch actions compared to hand-touch actions do not necessarily evoke a reduction of mu power. Thus, we conclude that reduction of mu frequency power is context-dependent during infants' action perception. Our results are interpreted in terms of motor system activity measured via changes in mu frequency band as being one important neural mechanism involved in action prediction and evaluation from early on.

Not so secret agents: Event-related potentials to semantic roles in visual event comprehension

Research across domains has suggested that agents, the doers of actions, have a processing advantage over patients, the receivers of actions. We hypothesized that agents as "event builders" for discrete actions (e.g., throwing a ball, punching) build on cues embedded in their preparatory postures (e.g., reaching back an arm to throw or punch) that lead to (predictable) culminating actions, and that these cues afford frontloading of event structure processing. To test this hypothesis, we compared event-related brain potentials (ERPs) to averbal comic panels depicting preparatory agents (ex. reaching back an arm to punch) that cued specific actions with those to non-preparatory agents (ex. arm to the side) and patients that did not cue any specific actions. We also compared subsequent completed action panels (ex. agent punching patient) across conditions, where we expected an inverse pattern of ERPs indexing the differential costs of processing completed actions asa function of preparatory cues. Preparatory agents evoked a greater frontal positivity (600-900ms) relative to non-preparatory agents and patients, while subsequent completed actions panels following non-preparatory agents elicited a smaller frontal positivity (600-900ms). These results suggest that preparatory (vs. non-) postures may differentially impact the processing of agents and subsequent actions in real time.

Bound to remember: Infants show superior memory for objects presented at event boundaries

Following Event Segmentation Theory (EST) adult memory is enhanced at event boundaries (EB). The present study set out to explore this in infancy. Sixty-eight 21-month-olds watched a cartoon with one of two objects (counterbalanced) inserted for 3s either at EB or between EB. Ten minutes later they watched both objects (familiar and novel) in a 10s Visual Paired Comparison (VPC) test while being eye-tracked. Furthermore, they were asked to point to the previous object. Based on EST, we hypothesized that objects inserted at EB would be processed more fully, resulting in improved memory compared to objects inserted between EB. Only infants with objects at EB exhibited memory evidenced by a transient familiarity preference for the first 3s of the test. Only 18 infants completed the pointing test, but all infants presented with objects at EB (10/10) pointed to the correct (familiar) object, which was not the case for the infants presented with objects between EB (5/8).

Occlusions at event boundaries during encoding have a negative effect on infant memory

The present study investigated the importance of Event Boundaries for 16- and 20-month-olds' (n=80) memory for cartoons. The infants watched one out of two cartoons with ellipses inserted covering the screen for 3s either at Event Boundaries or at Non-Boundaries. After a two-week delay both cartoons (one familiar and one novel) were presented simultaneously without ellipses while eye-tracking the infants. According to recent evidence a familiarity preference was expected. However, following Event Segmentation Theory ellipses at Event Boundaries were expected to cause greater disturbance of the encoding and hence a weaker memory trace evidenced by reduced familiarity preference, relative to ellipses at Non-Boundaries. The results suggest that overall this was the case, documenting the importance of Boundaries for infant memory. Furthermore, planned analyses revealed that whereas the same pattern was found when looking at the 20-month-old infants, no significant difference was found between the two conditions in the youngest age-group.

Action Interrupted: Processing of Movement and Breakpoints in Toddlers and Adults

From early in development, segmenting events unfolding in the world in meaningful ways renders input more manageable and facilitates interpretation and prediction. Yet, little is known about how children process action structure in events comprised of multiple coarse-grained actions. More importantly, little is known about the time-course of action processing in young children or about the specific features that recruit attention. This is particularly true when we consider action that pauses unexpectedly-as actions sometimes do-violating the expectation of a continuous unfolding of motion. We assessed visual preference to intact and disrupted actions embedded within a multi-action event in toddlers and adults. In one condition, pauses were inserted at intact action boundaries whereas in the other condition they disrupted action. Attention in both groups was recruited to the disrupted relative to intact events. Time-course analyses, however, revealed developmental differences in sensitivity to the movement features (e.g., motion, pauses, and transitions) of disrupted events.

Dissociating associative and motor aspects of action understanding: Processing of dual-ended tools by 16-month-old infants

When learning about the functions of novel tools, it is possible that infants may use associative and motoric processes. This study investigated the ability of 16-month-olds to associate the orientation in which an actor held a dual-function tool with the actor's prior demonstrated interest in one of two target objects, and their use of the tool on that target. The actors' hand posture did not differ between conditions. The infants were shown stimuli in which two actors acted upon novel objects with a novel tool, each actor employing a different function of the tool. Using an eye-tracker, infants' looking time at images depicting the actors holding the tool in an orientation congruent or incongruent with the actor's goal was measured. Infants preferred to look at the specific part of the tool that was incongruent with the actor's goal. Results show that the association formed involves the specific part of the tool, the actor, and the object the actor acted upon, but not the orientation of the tool. The capacity to form such associations is demonstrated in this study in the absence of motor information that would allow 16-month-olds to generate a specific representation of how the tool should be held for each action via mirroring processes.