The development of children's and adults' use of kinematic cues for visual anticipation and verbal prediction of action.

Expectations about how others' actions unfold in the future are crucial for our everyday social interactions. The current study examined the development of the use of kinematic cues for action anticipation and prediction in 3-year-olds, 4-year-olds, 10-year-olds, and adults in two experiments. Participants observed a hand repeatedly reaching for either a close or far object. The motor kinematics of the hand varied depending on whether the hand reached for the close or far object. We assessed whether participants would use kinematic cues to visually anticipate (Experiment 1; N=98) and verbally predict (Experiment 2; N=80) which object the hand was going to grasp. We found that only adults, but not 3- to 10-year-olds, based their visual anticipations on kinematic cues (Experiment 1). This speaks against claims that action anticipations are based on simulating others' motor processes and instead provides evidence that anticipations are based on perceptual mechanisms. Interestingly, 10-year-olds used kinematic cues to correctly verbally predict the target object, and 4-year-olds learned to do so over the trials (Experiment 2). Thus, kinematic cues are used earlier in life for explicit action predictions than for visual action anticipations. This adds to a recent debate on whether or not an implicit understanding of others' actions precedes their ability to verbally reason about the same actions.

The ontogeny of efficient second-order action planning: The developing interplay of controlled and habitual processes in goal-directed actions.

The ability to act efficiently plays an important role in everyday human life. The current study investigated efficient motor planning in 2- to 14-year-old children and adults (N = 246) in two different object manipulation tasks that involved everyday objects (a cup and a spoon). Importantly, we manipulated whether or not the efficient controlled grasp was incongruent with the habitual use of the object. We assessed to what extent participants planned their grasping action in an anticipatory controlled manner or relied on the habitual use of an object. We found the ability of efficient movement planning to be correlated between the two conceptually different tasks. Furthermore, the interplay of controlled and habitual processes of action control showed different developmental patterns for the two tasks and does not indicate a simple linear developmental trend. Thus, this study expands our knowledge on the ontogeny of efficient motor planning and highlights the developmental dynamics of the interplay of controlled and habitual processes in goal-directed action control.