Figure 8.

Difference between the mean projection errors obtained by using the random sets, e_ri, and the projection errors corresponding to three sets of synergies, e_si (i.e., I_i = e_ri − e_si for each set i), for solving the reversal testing tasks. The sets of synergies correspond to increasingly more general classes of tasks; i.e., two, four, and six free task-parameters (right diagonal blue, green, and left diagonal red bars, respectively). This difference reduces for increasingly more general tasks, showing that the effectiveness of the reduction phase decreases as the actuations become less regular.