Figure 3.

The dual processor model (DPM) involves a cognitive processor (CP) and a motor processor (MP) that together drive three distinct modes of sequence execution, through long-term sequential knowledge and the temporary storage in a motor buffer (in the case of motor chunking). S_n and R_n denote the current stimulus and corresponding response within the sequence, respectively. Black arrows and boxes denote the relevant processing routes. (A) In the reaction mode, responses are selected by the cognitive processor (CP) on the basis of S-R translation. (B) Ongoing response selection by the CP is facilitated by the first, still weak, sequence knowledge that develops. (C) Motor chunks have developed, and the CP selects these motor chunks, loads them in the motor buffer, from where the motor processor can execute them. Please note (I) that panel C also depicts the assumption of DPM that there can be a race between two response processes: the triggering of responses by the motor processor reading response related codes from the motor buffer, and response selection by the cognitive processor on basis of continued S-R translation or explicit sequence knowledge (dark gray arrow with black lining). Also note (II) that a fourth theoretical possibility is not depicted here, namely that the CP can load the motor buffer not by selecting motor chunks, but rather by (the slower process of) selecting and loading individual response elements of a (relatively) unfamiliar sequence.