The key grouping structures relevant to metrical stress theory are the categories of the prosodic hierarchy. Prosodic categories can be divided into two types: interface categories and rhythmic categories. The interface categories are the utterance, the intonational phrase, the phonological phrase, and the prosodic word. The rhythmic categories are the foot, the syllable, and the mora. The key principles governing prosodic grouping are Constituency, Strict Succession, and Headedness. Constituency insists that prosodic groupings occur in the dominance relationship specified by the prosodic hierarchy. Strict Succession insists that phonological representations not skip prosodic categories moving lower to higher in hierarchy. Headedness insists that every instance of a prosodic category designate one of its immediate constituents as its head (its most prominent constituent). The combination of Headedness and Strict Succession insists that phonological representations not skip prosodic categories moving in the either direction, either lower to higher or higher to lower. Two special configurations play key roles in the theory: recursion and overlap. Interface categories may exhibit recursion, but recursion of rhythmic categories is prohibited by the Simple Layering condition. Instances of the same prosodic category may overlap so that they share a constituent.

The relationship between the metrical grid and the prosodic hierarchy and the relation between prosodic structure and syntactic structure are both relationships and relations of Correspondence. Correspondence is a representational link between two representational objects. Entries on the metrical grid and instances of prosodic categories may correspond, and instances of prosodic categories and instances of syntactic categories may correspond. Mapping is the correspondence relation between instances of prosodic categories and entries on the metrical grid. The mapping relation is one of the key factors influencing the grid’s construction. Mapping is governed by a handful of key principles, including Hierarchy Coordination. The prosodic hierarchy and the metrical grid are both hierarchies and they map to each other as hierarchies. Mapping is required by the violable MAP family of constraints, constraints that require prosodic categories to map to grid entries. The MATCH family of constraints requires faithful correspondence between prosodic categories and syntactic or morphological categories. It requires both that the correspondence relation exist and that that correspondents share key elements. Simple MATCH constraints require correspondents to have exactly the same set of terminal elements. LexMatch constraints require correspondents to have the same set of lexical terminal elements. LexMatch constraints ignore functional terminal elements.

The present study investigated the production of lexical stress by native speakers of English (NE), Arabic learners of English (ALE), and native speakers of Arabic (NA). In the first experiment, minimal pairs (e.g., ‘con.flict, con.’flict) were recorded by 8 native speakers of English and 16 (8 advanced and 8 beginning) learners. For comparison, a second experiment examined acoustic cues used to indicate stress in 8 native Arabic speakers. In both experiments, four acoustic cues were examined: duration, fundamental frequency, amplitude, and second formant frequency. Results showed that NE consistently used all four cues to signal stress, with longer duration, higher fundamental frequency, higher amplitude, and less reduced vowel quality for stressed syllables. Advanced ALE, but not the beginning ALE, made distinctions in duration and amplitude similar to the duration and amplitude cues used by NE. For fundamental frequency, both advanced and beginning ALE produced even higher fundamental frequency values for stressed syllables than NE and both learner groups produced full (unreduced) vowels in stressed and unstressed syllables. Implications for acoustic cues to lexical stress in English as a second language are discussed.

In this study, segmental and prosodic properties of word-length stimuli were assessed together. Six talkers from 5 L1 backgrounds (American English, Hindi, Korean, Mandarin, and Spanish) were recorded reading English stop-initial trochaic words. The productions were played for 20 monolingual American English-speaking listeners rated the accentedness of each talker. For each token, the deviation from native English productions was determined for segmental (VOT, vowel quality) and three prosodic properties (ratios of duration, intensity, f0 across the two syllables). For each non-native language background, a linear mixed-effects regression model was created to predict accentedness ratings from the phonetic deviations, and the significance of each fixed effect was examined. In each model, the significant predictors included both segmental and prosodic properties. For Hindi and Spanish talkers, the single best predictor was segmental; however, for Korean and Mandarin talkers, the single best predictor was prosodic. Thus, even for short stimuli, both segmental and prosodic information must be considered in accounting for accentedness judgments. We conclude that listeners are sensitive to the different ways that foreign accent may be manifested across different non-native backgrounds.