Is stuttering due to a deficient comprehension of linguistic structures?

The results of two studies with 19 stutterers of two educational levels show that stutterers with more education stutter less but judge boundary depths in sentences better than stutterers with less education. This finding suggests that, among stutterers, the amount of stuttering and the comprehension of linguistic structures correlate negatively. These results gave rise to the loaded assumption that stuttering may be based on a deficiency in central linguistic processes. However, a third study with 20 nonstutterers leads to the conclusion that this does not hold for the imaginable continuum from nonstuttering to stuttering: for both educational levels nonstutterers do not differ from stutterers in judging constituent boundaries. This outcome does not support that stuttering may be based on a shortcoming in central linguistic processes but rather on a shortcoming in speech production at the level of articulation.