Tool-Use Training in a Species of Rodent: The Emergence of an Optimal Motor Strategy and Functional Understanding
Figure 1
Performance example of tool use and levels of training.
A. An example of the performance by one degu at Level 2a. Right column: Video frames depicting representative epochs during a single attempt at food retrieval using a rake tool. In the beginning, the degu failed to draw in the sunflower seed (1,100 ms). The animal then adjusted the position of the tool carefully after it observed the position of the food (2,000 ms) and pulled in the reward successfully (3,200 ms). Left column: Trajectories of the tip of the tool between the previous and following frames (red lines) are superimposed on the trajectory during the entire course of retrieval (gray lines, identical for all frames). Orientation and position of the rake (green squares and bars) and the location of food (orange dots) are also shown (traced from the photographs in the right column). B. Levels of training. At Level 1a, the animal can simply pull the tool toward itself. At Level 1b, the distance to pull is increased. At Level 2a, the animal has to make a lateral movement before pulling the tool toward itself
. At Level 2b, the animal has to place the tool beyond the reward before pulling.