One of the most challenging tasks for language - learning infants and second language ( L2 ) - learning adults is to segment the continuous stream of speech that surrounds them , and , following this , to acquire a lexicon . Both speech segmentation and lexical acquisition are known to be facilitated by phonotactics , i.e . , language - specific restrictions on how phonemes may combine . This dissertation addresses questions regarding the representation and acquisition of such phonotactic knowledge in a native language and an L2 . Five experimental studies are presented . The first three studies , using the artificial language learning paradigm , reveal that segmentation is influenced by structural phonotactic knowledge of OCP - PLACE , a restriction against pairs of consonants sharing the feature [ Place ] . It is shown that this knowledge is used only by native listeners or advanced L2 learners of a language restricted by the constraint . This suggests a language - specific acquisition from the input . The third study , with infants , shows that this input is continuous speech rather than the lexicon . The remaining two studies demonstrate that abstract phonotactic knowledge of syllable structure is represented separately from specific probabilistic knowledge , as the two have separate effects on lexical acquisition in a short - term memory recall task . Moreover , results from L2 learners suggest that probabilistic knowledge can be acquired independently of structural knowledge of the L2 . While most studies have looked at the influence of specific representations of phonotactic probability , here it is shown that representations of abstract structural constraints also influence processing . Moreover , it is demonstrated that both types of phonotactic representations are acquired from the input .