Closer perceptual inspection of the individual utterances reveals that from 15% noise and higher, the model’s speech output is highly deteriorated. This finding applies to both deficits, but manifests itself differently, which seems to be related to the quality of the systemic mapping. In the case of MPD, the quality of the speech output starts to decrease at noise levels of 15% and higher. In the case of MPD+APD, the quality of the systemic mapping shows a very strong and consistent decrease with increased noise level, and at a noise level of 15% the sum-squared Euclidean error is already twice as large as in the baseline condition. Under these circumstances, the systemic mapping becomes so unspecified that every utterance is strongly neutralized and reduces to schwa. Hence the inverse relation between speech quality and intelligible for noise levels of 15% and higher: the model’s productions reduce to schwa, but these schwa’s are produced well without much distortion or irregularities. In the case of MPD, results do not show this strong effect of underspecification of the systemic mapping and correspondingly no strong neutralization effect in the speech production after imitation learning. Under circumstances of a motor processing deficit only (MPD), systemic mapping quality decreases from noise levels of 15% and up, but only relatively mildly. Thus, the effect of increased severity is different from the effect regarding MPD+APD. For MPD, the increase in severity causes primarily a strong decrease in speech quality. When noise levels exceed 10%, the speech production features so much distortion and irregularities that it does not resemble speech anymore. For these reasons, we limited the further analysis of both implemented deficits to the first two levels of severity (noise levels of 5% and 10%).