The process of learning tool-use movements in monkeys: the initial process of picking up and using forceps

The initial process of learning forceps-use movements was studied in two monkeys who had already learned to pick a piece of food using a hand-held forceps. When the task was changed and the monkeys had to reach-to-grasp the forceps themselves, they did not perform the movement and required help to initiate the movement. When prompted, they performed an act mimicking the use of forceps but with empty hands. After around 160 guided trials, they initiated the process themselves. Self-initiation occurred initially sporadically along with the guided trials and was always after another 100 trials. The self-initiated actions were characterized by a consistent basic pattern of movements accompanied by a specific gaze, and the whole sequence of actions was completed whenever self-initiated actions occurred. We suggest that the learning process until the establishment of self-initiation consisted of understanding the task, shaping the basic scheme of action, and realizing the scheme as a series of movements; thus, providing a basis for further learning. Comparison of movement segments with and without experience suggested that experience remains effective in one particular segment but in learning an action composed of many such segments, these have to be practiced together for the action to constitute a functional entity.