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.

Six-month-old infants expect agents to minimize the cost of their actions

Substantial evidence indicates that infants expect agents to move directly to their goals when no obstacles block their paths, but the representations that articulate this expectation and its robustness have not been characterized. Across three experiments (total N=60), 6-month-old infants responded to a novel, curvilinear action trajectory on the basis of its efficiency, in accord with the expectation that an agent will move to its goal on the least costly path that the environment affords. Infants expected minimally costly action when presented with a novel constraint, and extended this expectation to agents who had previously acted inefficiently. Infants' understanding of goal-directed action cannot be explained alone by sensitivity to specific features of agent's actions (e.g. agents tend to move on straight paths, along supporting surfaces, when facing their goals directly) or extrapolations of agents' past actions to their future ones (e.g. if an agent took the shortest path to an object in the past, it will continue to do so in the future). Instead, infants' reasoning about efficiency accords with the overhypothesis that agents minimize the cost of their actions.

Understanding human original actions directed at real-world goals: the role of the lateral prefrontal cortex

Adaptive, original actions, which can succeed in multiple contextual situations, require understanding of what is relevant to a goal. Recognizing what is relevant may also help in predicting kinematics of observed, original actions. During action observation, comparisons between sensory input and expected action kinematics have been argued critical to accurate goal inference. Experimental studies with laboratory tasks, both in humans and nonhuman primates, demonstrated that the lateral prefrontal cortex (LPFC) can learn, hierarchically organize, and use goal-relevant information. To determine whether this LPFC capacity is generalizable to real-world cognition, we recorded functional magnetic resonance imaging (fMRI) data in the human brain during comprehension of original and usual object-directed actions embedded in video-depictions of real-life behaviors. We hypothesized that LPFC will contribute to forming goal-relevant representations necessary for kinematic predictions of original actions. Additionally, resting-state fMRI was employed to examine functional connectivity between the brain regions delineated in the video fMRI experiment. According to behavioral data, original videos could be understood by identifying elements relevant to real-life goals at different levels of abstraction. Patterns of enhanced activity in four regions in the left LPFC, evoked by original, relative to usual, video scenes, were consistent with previous neuroimaging findings on representing abstract and concrete stimuli dimensions relevant to laboratory goals. In the anterior left LPFC, the activity increased selectively when representations of broad classes of objects and actions, which could achieve the perceived overall behavioral goal, were likely to bias kinematic predictions of original actions. In contrast, in the more posterior regions, the activity increased even when concrete properties of the target object were more likely to bias the kinematic prediction. Functional connectivity was observed between contiguous regions along the rostro-caudal LPFC axis, but not between the regions that were not immediately adjacent. These findings generalize the representational hierarchy account of LPFC function to diverse core principles that can govern both production and comprehension of flexible real-life behavior.

Preverbal infants identify emotional reactions that are incongruent with goal outcomes

Identifying the goal of another agent's action allows an observer to make inferences not only about the outcomes the agent will pursue in the future and the means to be deployed in a given context, but also about the emotional consequences of goal-related outcomes. While numerous studies have characterized the former abilities in infancy, expectations about emotions have gone relatively unexplored. Using a violation of expectation paradigm, we present infants with an agent who attains or fails to attain a demonstrated goal, and reacts with positive or negative affect. Across several studies, we find that infants' attention to a given emotional display differs depending on whether that reaction is congruent with the preceding goal outcome. Specifically, infants look longer at a negative emotional display when it follows a completed goal compared to when it follows a failed goal. The present results suggest that infants' goal representations support expectations not only about future actions but also about emotional reactions, and that infants in the first year of life can relate different emotional reactions to conditions that elicit them.