Action perception in infancy: the plasticity of 7-month-olds' attention to grasping actions.

The present study investigates the plasticity of 7-month-old infants' orienting of attention during their perception of grasping actions. Previous research has shown that when infants observe a grasping hand, they shift their attention in line with the grasping direction, which is indicated by a reliable priming effect in this direction. The mechanisms behind this priming effect are largely unknown, and it is unclear how malleable this priming effect is with respect to a brief exposure to novel action-target contingencies. In a spatial-cueing paradigm, we presented a series of training trials prior to a series of test trials. These training sequences significantly modulated infants' attention. This suggests that action perception, when assessed through shifts of attention, is not solely based on the infants' grasping experience but quickly adapts to context-specific observed regularities.

Infants' object processing is guided specifically by social cues.

Previous studies showed that the movements of another person's eyes and head guides infants' attention and promotes social learning by leading to enhanced encoding of cued objects. However, it is an open question whether social features like eyes are required or if the lateral movement of any arbitrary stimulus can elicit similar effects. The current experiments investigate the effects of the movement of a nonsocial cue and a perceptually similar social cue on object processing in 4-month-olds using event-related potentials (ERPs). Infants were presented with one of two central cues, either a box with a checkerboard pattern or a box with eye-like features on the front, which turned to one side. The cue thereby either turned toward a novel object or turned away from it. Afterwards, the object was presented again and ERPs in response to these previously cued or uncued objects were compared. When the nonsocial box served as the cue, no difference in neural processing of previously cued and uncued objects was found. In contrast, when the box with eyes served as the cue, we found an enhanced positive slow wave (PSW) for uncued as compared to cued objects. While the turning of the box with eyes promoted the encoding of cued objects, uncued objects needed enhanced activity for processing when presented for a second time. Results suggest that not every dynamic cue can influence infants' object processing but that the presence of a basic social characteristic like isolated schematic eyes is sufficient to enhance social learning processes in early infancy. This hints on a specific sensitivity of the infant brain to social information which helps infants to focus on relevant information in the environment during social learning.

Effects of movement distance, duration, velocity, and type on action prediction in 12-month-olds.

The goal of the present study was to test the influence of the spatial and temporal dynamics of observed manual actions on infants' action prediction. Twelve-month-old infants were presented with reach-and-transport actions performed by a human agent. Movement distance, duration, and - resulting from the two - movement velocity were systematically varied. Action prediction was measured via the latency of gaze arrival at target in relation to agent's hand. The results showed a general effect of all parameters on the infants' perception of goal-directed actions: Infants were more likely to predict the action goal the longer the movement distance was, the longer the movement duration was, and the slower the movement velocity was. In addition, they were more likely to predict the goal of a reaching than a transport action. The present findings extent previous findings by showing that infants are not only sensitive to differences in distances, durations, and velocities at early age but that these factors have a strong impact on the prediction of the goal of observed actions.

Spatial orienting following dynamic cues in infancy: grasping hands versus inanimate objects.

Movement perception facilitates spatial orienting of attention in infants (Farroni, Johnson, Brockbank, & Simion, 2000). In a series of 4 experiments, we investigated how orienting of attention in infancy is modulated by dynamic stimuli. Experiment 1 (N = 36) demonstrated that 5-month-olds as well as 7-month-olds orient to the direction of a dynamically grasping human hand. Experiment 2 (N = 36) showed that 7-month-olds orient covertly to direction of a geometrical shape moving on the trajectory of the grasping movement, but 5-month-olds do not. Experiment 3 (N = 18) showed that mere linear translating object movement does not elicit covert orienting of attention in 7-month-olds. In Experiment 4 (N = 18), we found that 7-month-olds process both grasping direction and movement direction, which resulted in increased reaction times when these cues conflicted. These findings suggest that orienting of attention reflects rapid detection of goal-directed agents. Five-month-olds need the information of both movement and grasping direction, whereas 7-month-olds can use each of these directional cues in isolation.