These two videos of Rona (4y 9m) and Will (3y 2m) were originally made to illustrate the emergence of planning for end-state-comfort concept. This they do well with Rona showing a transition to end state comfort planning over repeated trials of turning beakers over. Will on the other hand stays with his preferred action despite twice starting the action with the hands initially positioned to allow for a comfortable end position.
Turning the beakers over with one hand is a novel experience and requires more attention, ongoing visual monitoring and elicits exploration of different options. When instructed to use only one hand they need to develop a different strategy. Both children manage to turn the beakers over with one hand. Will sticks to using his preferred pattern but Rona starts to explore changing her start position to achieve a comfortable end position.
Will ending action in an uncomfortable position
Rona adapting initial grasp to end action in a comfortable position
Interestingly Will initiates the turning over action with the forearm in pronation to allow for a comfortable end position, but before he grasps the beaker he reverts to grasping with the forearm in a more comfortable mid-range position.
Rona (4y 9m) turning over cups
Notice the difference in visual information pickup
Besides observing Roan's emergent tendency to plan for end state comfort, I was also struck by the different use of visual information pick up between the well practised two handed sequence of movements and the novel one handed action.
In the two handed action the hands movements are smoothly coordinated in space and time and brief periods of visual fixation on the beaker is all that are needed to get the needed information about the position of the beaker. On the other hand when using the unpracticed one hand strategy, Roan appears to need online visual guidance for controlling the action.
Will (3y 2m) turning over beakers