Horizontal: number of moves. Vertical: execution time (normalized). A: unbounded memory, U(N). B: bounded memory, B(N), I(task) (grey zone) and I(N), i.e., average of I(task), C: detail: all indicators together, N< = 4. According to Shallice (1982), with 4 moves or more, the supervisory attentional system is engaged.