Figure 2.

(A) Overview of the body-central directions (inward and outward, in blue) and the keyboard-central directions (ascending and descending, in green). (B) Predictions of the two hypotheses. If the irregularity traces mostly stem from neuromuscular constraints, we expect traces originating from the same movements to be similar. If they originate mostly from residual expression, we expect traces producing the same sounds to be similar. (C) Experimental results, in line with the neuromuscular hypothesis.