Structural regularities in language have often been attributed to symbolic or statistical general purpose computations, whereas perceptual factors influencing such generalizations have received less interest. Here, we use phonotactic-like constraints as a case study to ask whether the structural properties of specific perceptual and memory mechanisms may facilitate the acquisition of grammatical-like regularities. Participants learned that the consonants C[subscript 1] and C[subscript 2] had to come from distinct sets in words of the form C[subscript 1]VccVC[subscript 2] (where the critical consonants were in word "edges") but not in words of the form cVC[subscript 1]C[subscript 2]Vc (where the critical consonants were in word middles). Control conditions ruled out attentional or psychophysical difficulties in word "middles." Participants did, however, learn such regularities in word middles when natural consonant classes were used instead of arbitrary consonant sets. We conclude that positional generalizations may be learned preferentially using edge-based positional codes, but that participants can also use other mechanisms when other linguistic cues are given. (Contains 4 footnotes and 4 figures.)