This may be because low frequency words are generally longer than high frequency words. Preschool children appear to stutter more on function words than on content words. More stutters occur on the first word of sentences than on other words. More stutters are observed on the first three words than on subsequent words. More stutters occur on initial sentences and paragraphs and at the beginning of discourse than in later parts.
More stutters occur on longer sentences than on shorter ones.
Same words read as a list tend to be stuttered less than when they are read as part of a sentence. There are many well-known conditions in which stuttering temporarily disappears or is significantly reduced. Nearly all stutterers experience this temporary amelioration indicating that the beneficial effects of these conditions are somehow related to the nature of stuttering itself rather than the persons who stutter. In contrast, the conditions that increase stuttering are less well established, tend to vary widely among stutterers and, for the most part, produce relatively small and inconsistent increases in stutters. This suggests that conditions that increase stuttering are tied to the particular experiences of individual stutterers and how they react to and deal with their experiences.