Although we have discussed the ways in which infants may take advantage of phonotactics to pro- mote vocabulary development, another direction of influence is likely to occur as well. The association between vocabulary size and phonotactic representations may occur because building a vocabulary provides infants with the data necessary to detect phonotactic patterns. By 18 or 19 months of age, infants may store a sufficient inventory of word forms to generalize about the frequency of various sound combinations. Developing this inventory supports the detection of new words that fit with prior experience as well as novel sound sequences that violate the phonotactic generalizations. In consid- ering this direction of influence, we are not arguing that rich vocabulary knowledge is the sole driver of phonotactic representations because by 9 months of age infants distinguish phonotactically legal versus illegal sequences and common versus rare sequences At these ages, infants have started to store representations of word forms and have started to comprehend words, but they do not yet have rich lexicons. The average comprehension vocabulary size is only approximately 40 words at 9 months of age. However, the presence of early phonotactic sensitivities in infants also does not mean that phonotactic repre- sentations are fully formed during infancy. Although early representations of native phonotactics may be an important foundation for word segmentation and word learning, there is ample room for further enrichment as vocabulary acquisition promotes the strengthening of phonotactic representa- tions and phonological representations more broadly.