The seeds of social learning: Infants exhibit more social looking for plants than other object types.

Infants must negotiate encounters with a wide variety of different entities over the course of the first few years of life, yet investigations of their social referencing behavior have largely focused on a limited set of objects and situations such as unfamiliar toys and the visual cliff. Here we examine whether infants' social looking strategies differ when they are confronted with plants. Plants have been fundamental to human life throughout our evolutionary history, and learning about which plants are beneficial and which are dangerous is a task that, for humans, cannot be achieved alone. Using an object exploration paradigm, we found that 8- to 18-month-old infants exhibited more social looking toward adults when confronted with plants compared to other object types. Further, this increased social looking occurred when infants first encountered plants, in the time before touching them. This social looking strategy puts infants in the best position to glean information from others before making contact with potentially dangerous plants. These findings provide a new lens through which to view infants' social information seeking behavior.

Categories and Constraints in Causal Perception.

When object A moves adjacent to a stationary object, B, and in that instant A stops moving and B starts moving, people irresistibly see this as an event in which A causes B to move. Real-world causal collisions are subject to Newtonian constraints on the relative speed of B following the collision, but here we show that perceptual constraints on the relative speed of B (which align imprecisely with Newtonian principles) define two categories of causal events in perception. Using performance-based tasks, we show that triggering events, in which B moves noticeably faster than A, are treated as being categorically different from launching events, in which B does not move noticeably faster than A, and that these categories are unique to causal events (Experiments 1 and 2). Furthermore, we show that 7- to 9-month-old infants are sensitive to this distinction, which suggests that this boundary may be an early-developing component of causal perception (Experiment 3).

Goal saliency boosts infants' action prediction for human manual actions, but not for mechanical claws.

Previous research indicates that infants' prediction of the goals of observed actions is influenced by own experience with the type of agent performing the action (i.e., human hand vs. non-human agent) as well as by action-relevant features of goal objects (e.g., object size). The present study investigated the combined effects of these factors on 12-month-olds' action prediction. Infants' (N=49) goal-directed gaze shifts were recorded as they observed 14 trials in which either a human hand or a mechanical claw reached for a small goal area (low-saliency goal) or a large goal area (high-saliency goal). Only infants who had observed the human hand reaching for a high-saliency goal fixated the goal object ahead of time, and they rapidly learned to predict the action goal across trials. By contrast, infants in all other conditions did not track the observed action in a predictive manner, and their gaze shifts to the action goal did not change systematically across trials. Thus, high-saliency goals seem to boost infants' predictive gaze shifts during the observation of human manual actions, but not of actions performed by a mechanical device. This supports the assumption that infants' action predictions are based on interactive effects of action-relevant object features (e.g., size) and own action experience.

The neural basis of non-verbal communication-enhanced processing of perceived give-me gestures in 9-month-old girls.

This study investigated the neural basis of non-verbal communication. Event-related potentials were recorded while 29 nine-month-old infants were presented with a give-me gesture (experimental condition) and the same hand shape but rotated 90°, resulting in a non-communicative hand configuration (control condition). We found different responses in amplitude between the two conditions, captured in the P400 ERP component. Moreover, the size of this effect was modulated by participants' sex, with girls generally demonstrating a larger relative difference between the two conditions than boys.

The neuropsychology of infants' pro-social preferences.

The current study is the first to investigate neural correlates of infants' detection of pro- and antisocial agents. Differences in ERP component P400 over posterior temporal areas were found during 6-month-olds' observation of helping and hindering agents (Experiment 1), but not during observation of identically moving agents that did not help or hinder (Experiment 2). The results demonstrate that the P400 component indexes activation of infants' memories of previously perceived interactions between social agents. This leads to suggest that similar processes might be involved in infants' processing of pro- and antisocial agents and other social perception processes (encoding gaze direction, goal directed grasping and pointing).

Infants' online perception of give-and-take interactions.

This research investigated infants' online perception of give-me gestures during observation of a social interaction. In the first experiment, goal-directed eye movements of 12-month-olds were recorded as they observed a give-and-take interaction in which an object is passed from one individual to another. Infants' gaze shifts from the passing hand to the receiving hand were significantly faster when the receiving hand formed a give-me gesture relative to when it was presented as an inverted hand shape. Experiment 2 revealed that infants' goal-directed gaze shifts were not based on different affordances of the two receiving hands. Two additional control experiments further demonstrated that differences in infants' online gaze behavior were not mediated by an attentional preference for the give-me gesture. Together, our findings provide evidence that properties of social action goals influence infants' online gaze during action observation. The current studies demonstrate that infants have expectations about well-formed object transfer actions between social agents. We suggest that 12-month-olds are sensitive to social goals within the context of give-and-take interactions while observing from a third-party perspective.

Goal certainty modulates infants' goal-directed gaze shifts.

We investigated whether 12-month-old infants rely on information about the certainty of goal selection in order to predict observed reaching actions. Infants' goal-directed gaze shifts were recorded as they observed action sequences in a multiple-goals design. We found that 12-month-old infants exhibited gaze shifts significantly earlier when the observed hand reached for the same goal object in all trials (frequent condition) compared with when the observed hand reached for different goal objects across trials (nonfrequent condition). Infants in the frequent condition were significantly more accurate at predicting the action goal than infants in the nonfrequent condition. In addition, findings revealed rapid learning in the case of certainty and no learning in the case of uncertainty of goal selection over the course of trials. Together, our data indicate that by the end of their first year of life, infants rely on information about the certainty of goal selection to make inferences about others' action goals.

The motor cortex is causally related to predictive eye movements during action observation.

We examined the hypothesis that predictive gaze during observation of other people's actions depends on the activation of corresponding action plans in the observer. Using transcranial magnetic stimulation and eye-tracking technology we found that stimulation of the motor hand area, but not of the leg area, slowed gaze predictive behavior (compared to no TMS). This result shows that predictive eye movements to others' action goals depend on a somatotopical recruitment of the observer's motor system. The study provides direct support for the view that a direct matching process implemented in the mirror-neuron system plays a functional role for real-time goal prediction.

Goal salience affects infants' goal-directed gaze shifts.

Around their first year of life, infants are able to anticipate the goal of others' ongoing actions. For instance, 12-month-olds anticipate the goal of everyday feeding actions and manual actions such as reaching and grasping. However, little is known whether the salience of the goal influences infants' online assessment of others' actions. The aim of the current eye-tracking study was to elucidate infants' ability to anticipate reaching actions depending on the visual salience of the goal object. In Experiment 1, 12-month-old infants' goal-directed gaze shifts were recorded as they observed a hand reaching for and grasping either a large (high-salience condition) or a small (low-salience condition) goal object. Infants exhibited predictive gaze shifts significantly earlier when the observed hand reached for the large goal object compared to when it reached for the small goal object. In addition, findings revealed rapid learning over the course of trials in the high-salience condition and no learning in the low-salience condition. Experiment 2 demonstrated that the results could not be simply attributed to the different grip aperture of the hand used when reaching for small and large objects. Together, our data indicate that by the end of their first year of life, infants rely on information about the goal salience to make inferences about the action goal.

Humans Anticipate the Goal of other People's Point-Light Actions.

This eye tracking study investigated the degree to which biological motion information from manual point-light displays provides sufficient information to elicit anticipatory eye movements. We compared gaze performance of adults observing a biological motion point-light display of a hand reaching for a goal object or a non-biological version of the same event. Participants anticipated the goal of the point-light action in the biological motion condition but not in a non-biological control condition. The present study demonstrates that kinematic information from biological motion can be used to anticipate the goal of other people's point-light actions and that the presence of biological motion is sufficient for anticipation to occur.