Disentangling the Role of Biphone Probability From Neighborhood Density in the Perception of Nonwords.

In six experiments we explored how biphone probability and lexical neighborhood density influence listeners' categorization of vowels embedded in nonword sequences. We found independent effects of each. Listeners shifted categorization of a phonetic continuum to create a higher probability sequence, even when neighborhood density was controlled. Similarly, listeners shifted categorization to create a nonword from a denser neighborhood, even when biphone probability was controlled. Next, using a visual world eye-tracking task, we determined that biphone probability information is used rapidly by listeners in perception. In contrast, task complexity and irrelevant variability in the stimuli interfere with neighborhood density effects. These results support a model in which both biphone probability and neighborhood density independently affect word recognition, but only biphone probability effects are observed early in processing.

Short-term exposure alters adult listeners' perception of segmental phonotactics.

This study evaluates the malleability of adults' perception of probabilistic phonotactic (biphone) probabilities, building on a body of literature on statistical phonotactic learning. It was first replicated that listeners categorize phonetic continua as sounds that create higher-probability sequences in their native language. Listeners were also exposed to skewed distributions of biphone contexts, which resulted in the enhancement or reversal of these effects. Thus, listeners dynamically update biphone probabilities (BPs) and bring this to bear on perception of ambiguous acoustic information. These effects can override long-term BP effects rooted in native language experience.

Vowel perception under prominence: Examining the roles of F0, duration, and distributional information.

This study investigates how prosodic prominence mediates the perception of American English vowels, testing the effects of F0 and duration. In Experiment 1, the perception of four vowel continua varying in duration and formants (high: /i-ɪ/, /u-ʊ/, non-high: /ɛ-ae/, /ʌ-ɑ/), was examined under changes in F0-based prominence. Experiment 2 tested if cue usage varies as the distributional informativity of duration as a cue to prominence is manipulated. Both experiments show that duration is a consistent vowel-intrinsic cue. F0-based prominence affected perception of vowels via compensation for peripheralization of prominent vowels in the vowel space. Longer duration and F0-based prominence further enhanced the perception of formant cues. The distributional manipulation in Experiment 2 exerted a minimal impact. Findings suggest that vowel perception is mediated by prominence in a height-dependent manner which reflects patterns in the speech production literature. Further, duration simultaneously serves as an intrinsic cue and serves a prominence-related function in enhancing perception of formant cues.

Vowel-internal cues to vowel quality and prominence in speech perception.

This study examines how variation in F0 and intensity impacts the perception of American English vowels. Both properties vary intrinsically as a function of vowel features in the speech production literature, raising the question of the perceptual impact of each. In addition to considering listeners' interpretation of either cue as an intrinsic property of the vowel, the possible prominence-marking function of each is considered. Two patterns of prominence strengthening in vowels, sonority expansion and hyperarticulation, are tested in light of recent findings that contextual prominence impacts vowel perception in line with these effects (i.e. a prominent vowel is expected by listeners to be realized as if it had undergone prominence strengthening). Across four vowel contrasts with different height and frontness features, listeners categorized phonetic continua with variation in formants, F0 and intensity. Results show that variation in level F0 height is interpreted as an intrinsic cue by listeners. Higher F0 cues a higher vowel, following intrinsic F0 effects in the production literature. In comparison, intensity is interpreted as a prominence-lending cue, for which effect directionality is dependent on vowel height. Higher intensity high vowels undergo perceptual re-calibration in line with (acoustic) hyperarticulation, whereas higher intensity non-high vowels undergo perceptual re-calibration in line with sonority expansion.

An automated method for detecting F 0 measurement jumps based on sample-to-sample differences.

An algorithm for detecting sudden jumps in measured F0, which are likely to be inaccurate measures, is introduced. The method computes sample-to-sample differences in F0 and, based on a user-defined threshold, determines whether a difference is larger than naturally produced F0 velocities, thus, flagging it as an error. Various parameter settings are evaluated on a corpus of 30 American English speakers producing different intonational patterns, for which F0 tracking errors were manually checked. The paper concludes in recommending settings for the algorithm and ways in which it can be used to facilitate analyses of F0 in speech research.

Asymmetrical roles of segment and pitch accent in Japanese spoken word recognition.

This study examines the roles of segment and pitch accent in Japanese spoken word recognition. In a lexical decision task, it replicates the finding of Cutler and Otake [(1999) J. Acoust. Soc. Am. 105(3), 1877-1888] that pitch accent restricts word activation with a more comprehensive, rigorous experimental design. Furthermore, results uncover an asymmetrical role of segment and pitch accent in word recognition in Japanese: words primed by a pitch accent-matching prime are recognized more slowly and less accurately than words primed by a segment-matching prime.

Infants' developing sensitivity to native language phonotactics: A meta-analysis.

We used Bayesian modeling to aggregate experiments investigating infants' sensitivity to native language phonotactics. Our findings were based on data from 83 experiments on about 2000 infants learning 8 languages, tested using 4 different methods. Our results showed that, unlike with artificial languages, infants do exhibit sensitivity to native language phonotactic patterns in a lab setting. However, the exact developmental trajectory depends on the phonotactic pattern being tested. Before 8 months, infants tuned into non-local dependencies between vowels: specifically, vowel harmony. Between 8- and 10-months, infants demonstrated a consistent sensitivity to both local dependencies and non-local consonant dependencies. Sensitivity to non-local vowel dependencies that are not based on harmony emerged only after 10-months. These findings provide a benchmark for future experimental and computational research on the acquisition of phonotactics.

Tonal cues to prosodic structure in rate-dependent speech perception.

This study explores how listeners integrate tonal cues to prosodic structure with their perception of local speech rate and consequent interpretation of durational cues. In three experiments, we manipulate the pitch and duration of speech segments immediately preceding a target sound along a vowel duration continuum (cueing coda stop voicing), testing how listeners' categorization of vowel duration shifts based on temporal and tonal context. We find that listeners perceive the presence of a phrasal boundary tone on a lengthened syllable as signaling a slowdown in speech rate, shifting perception of vowel duration, with effects that are additive when crossed in a 2 × 2 (pitch × duration) design. However, an asymmetrical effect of pitch and duration is found in an explicit duration judgement task in which listeners judge how long a pre-target syllable sounds to them. In explicit rate judgement, only durational information is consequential, unlike the categorization task, suggesting that integration of tonal and durational prosodic cues in rate-dependent perception is limited to implicit processing of speech rate. Results are discussed in terms of linguistic information in rate-dependent speech processing, the integration of prosodic cues, and implicit and explicit rate processing tasks.

Rhythmic and speech rate effects in the perception of durational cues.

Listeners' perception of temporal contrasts in spoken language is highly sensitive to contextual information, such as variation in speech rate. The present study tests how rate-dependent perception is also mediated by distal (i.e., temporally removed) rhythmic patterns. In four experiments the role of rhythmic alternations and their interaction with speech rate effects are tested. Experiment 1 shows proximal speech rate (contrast) effects obtain based on changes in local context. Experiment 2 shows that these effects disappear with the addition of distal rhythmic alternations, indicating that rhythmic grouping shifts listeners' perception, even when proximal context conflicts. Experiments 3 and 4 explore how orthogonal variation in overall speech rate impacts these effects and finds that trial-to-trial (i.e., global) speech rate variation eliminates rhythmic grouping effects, both with and without variation in proximal (immediately preceding) context. Together, these results suggest a role for rhythmic patterning in listeners' processing of durational cues in speech, which interacts in various ways with proximal, distal, and global rate contexts.

Contextual prominence in vowel perception: Testing listener sensitivity to sonority expansion and hyperarticulation.

High front vowels have been shown to undergo two competing forms of acoustic (and articulatory) modulation due to prosodic prominence-(1) hyperarticulation: more extreme high/front articulations under prominence and (2) sonority expansion: more open articulations, allowing more energy to radiate from the mouth. This study explores how these effects translate into listeners' perception of the contrast between the vowels /i/ and /ɪ/. Results show that listeners uniformly expect a hyperarticulated vowel (acoustically) under prominence, and adjust categorization of an F1/F2 continuum accordingly. Results are discussed in relation to production findings and possible accounts of why listeners favor hyperarticulation in perception.

Intonational Structure Influences Perception of Contrastive Vowel Length: The Case of Phrase-Final Lengthening in Tokyo Japanese.

Recent research has proposed that listeners use prosodic information to guide their processing of phonemic contrasts. Given that prosodic organization of the speech signal systematically modulates durational patterns (e.g., accentual lengthening and phrase-final (PF) lengthening), listeners' perception of durational contrasts has been argued to be influenced by prosodic factors. For example, given that sounds are generally lengthened preceding a prosodic boundary, listeners may adjust their perception of durational cues accordingly, effectively compensating for prosodically-driven temporal patterns. In the present study we present two experiments designed to test the importance of pitch-based cues to prosodic structure for listeners' perception of contrastive vowel length (CVL) in Tokyo Japanese along these lines. We tested if, when a target sound is cued as being PF, listeners compensatorily adjust categorization of vowel duration, in accordance with PF lengthening. Both experiments were a two-alternative forced choice task in which listeners categorized a vowel duration continuum as a phonemically short or long vowel. We manipulated only pitch surrounding the target sound in a carrier phrase to cue it as intonational phrase final, or accentual phrase medial. In Experiment 1 we tested perception of an accented target word, and in Experiment 2 we tested perception of an unaccented target word. In both experiments, we found that contextual changes in pitch influenced listeners' perception of CVL, in accordance with their function as signaling intonational structure. Results therefore suggest that listeners use tonal information to compute prosodic structure and bring this to bear on their perception of durational contrasts in speech.

Perceptual integration of pitch and duration: Prosodic and psychoacoustic influences in speech perception.

Two experiments explored how pitch influences perception of vowel duration as a cue to voicing in light of (1) psychoacoustic interactions between pitch and duration and (2) predicted compensatory effects based on the patterning of pitch and duration in the accentual/prominence-marking system of English. Listeners categorized a "coat"-"code" vowel duration continuum with pitch height on the vowel manipulated. In experiment 1 the expected psychoacoustic effect was observed. In experiment 2 the continuum was altered, highlighting pitch as a prosodic property, resulting in predicted compensatory effects. Results thus indicate prosodic patterns can mediate the perception of durational cues in isolated words.

Phrase-final lengthening modulates listeners' perception of vowel duration as a cue to coda stop voicing.

The present study addresses how listeners may be sensitive to temporal regularities associated with prosody in their perception of durational segmental cues. Specifically, this study tests whether expectations about phrase-final lengthening mediate listeners' categorization of a "coat"∼"code" vowel duration continuum, where vowel duration cues stop voicing. Prosodic position of the target was manipulated such that it was either medial, or final in a carrier phrase. Results indicate that this prosodic manipulation influences categorization such that listeners effectively require longer vowel duration for a "code" response when the target is phrase-final, suggesting that prosodic patterns can modulate listeners' processing of temporal cues.