Introduction When a child is taught to correct an error sound essentially two processes are involved. A new sound (the standard sound) is acquired either as an isolated element or in a syllable. After the sound is well learned, children are instructed to use their new sound in words. This phase is a difficult point in, the training program, since the incorrect sound competes with the standard sound causing difficulty in “carry-over.” Recently, it has been observed that recall of speech sounds to pictorial stimuli is increased when the substituted sound and the original sound are phonetically similar (Winitz and Bellerose, 1972a), suggesting that the original sound (the error sound) may act as a facilitator rather than as a competitor. Apparently, facilitation takes place because the error sound reinstates all but a few of the distinctive features of the standard sound. We know that newly acquired sounds are difficult to maintain over time (e.g., Shelton, Johnson and Amdt, 1972). It is very possible, then, that facilitation produces interference. Interference is defined as competition between the error sound and the standard sound (Winitz and Bellerose, 1972a,b). The resulting competition is, however, nonmotor, as previous research indicates that over long intervals of time retrieval is difficult, although there is little loss in imitative ability (Winitz and Bellerose, 1972a,b). An example will be helpful here. A young child, who initially substituted 101 for is/, has been taught to produce a correct Is/, imitatively, in response to pictures, and when reading and speaking. The latter three test situations, reading, describing pictures and talking, will be referred to as retrieval functions. This child has no difficulty imitating the /s/ sound correctly at the beginning of each clinical session, but generally has difficulty with /s/ in tests of retrieval in the clinic and outside of the clinic. Our interpretation (Winitz and Bellerose, 1972a) is that /O/ facilitates the recall of Is/, but, since /O/ and /s/ are phonetically similar, the higher habit strength of