A large body of empirical research demonstrates that people exploit a wide variety of cues for the segmentation of continuous speech in artificial languages, including rhythmic properties, phrase boundary cues, and statistical regularities. However, less is known regarding how the different cues interact. In this study we addressed the question of the relative importance of lexical stress, phrasal prominence, and transitional probabilities (TP) between adjacent syllables for the segmentation of an artificial language. We explored how duration increase, pitch rise, and the combination of duration and pitch on the antepenultimate, the penultimate, and the final syllable of a three-syllabic word affect segmentation by native speakers of Italian. Our results indicate that, if the most frequent location of stress in the participants' native language and a lengthened syllable in the artificial language do not coincide, segmentation is disrupted. If there is no conflict between the location of stress in the native language of the participant and the lengthened syllable in the artificial language, segmentation is neither impeded nor facilitated. Pitch marked the edges of the TP-defined words in a continuous speech stream. When TPs and pitch cues are in conflict, segmentation fails; if pitch rise coincides with the edges of TP words, segmentation succeeds, but is not facilitated. Phrasal prominence comprising both pitch and duration facilitates segmentation when aligned with the word edges. Our findings show that language-specific peculiarities of how nuclear pitch accents are realized in the native language of the listener might interact with statistical cues in the segmentation of an unfamiliar language.

The development of speech rhythm in second language (L2) acquisition was investigated. Speech rhythm was defined as durational variability that can be captured by the interval-based rhythm metrics. These metrics were used to examine the differences in durational variability between proficiency levels in L2 English spoken by French and German learners. The results reveal that durational variability increased as L2 acquisition progressed in both groups of learners. This indicates that speech rhythm in L2 English develops from more syllable-timed toward more stress-timed patterns irrespective of whether the native language of the learner is rhythmically similar to or different from the target language. Although both groups showed similar development of speech rhythm in L2 acquisition, there were also differences: German learners achieved a degree of durational variability typical of the target language, while French learners exhibited lower variability than native British speakers, even at an advanced proficiency level.

It is widely accepted that duration can be exploited as phonological phrase final lengthening in the segmentation of a novel language, i.e., in extracting discrete constituents from continuous speech. The use of final lengthening for segmentation and its facilitatory effect has been claimed to be universal. However, lengthening in the world languages can also mark lexically stressed syllables. Stress-induced lengthening can potentially be in conflict with right edge phonological phrase boundary lengthening. Thus the processing of durational cues in segmentation can be dependent on the listener's linguistic background, e.g. on the specific correlates and unmarked location of lexical stress in the native language of the listener. We tested this prediction and found that segmentation by both German and Basque speakers is facilitated when lengthening is aligned with the word final syllable and is not affected by lengthening on either the penultimate or the antepenultimate syllables. Lengthening of the word final syllable, however, does not help Italian and Spanish speakers to segment continuous speech, and lengthening of the antepenultimate syllable impedes their performance. We have also found a facilitatory effect of penultimate lengthening on segmentation by Italians.These results confirm our hypothesis that processing of lengthening cues is not universal, and interpretation of lengthening as a phonological phrase final boundary marker in a novel language of exposure can be overridden by the phonology of lexical stress in the native language of the listener.3