Publications

Abstract

This study tests whether potential differences in the perceptual robustness of speech sounds influence continuous-speech processes. Two phoneme-monitoring experiments examined place assimilation in Korean. In Experiment 1, Koreans monitored for targets which were either labials (/p,m/) or alveolars (/t,n/), and which were either unassimilated or assimilated to a following /k/ in two-word utterances. Listeners detected unaltered (unassimilated) labials faster and more accurately than assimilated labials; there was no such advantage for unaltered alveolars. In Experiment 2, labial–velar differences were tested using conditions in which /k/ and /p/ were illegally assimilated to a following /t/. Unassimilated sounds were detected faster than illegally assimilated sounds, but this difference tended to be larger for /k/ than for /p/. These place-dependent asymmetries suggest that differences in the perceptual robustness of segments play a role in shaping phonological patterns.

Abstract

Listeners heard an ambiguous /f-s/ in nonword contexts where only one of /f/ or /s/ was legal (e.g., frul/*srul or *fnud/snud). In later categorisation of a phonetic continuum from /f/ to /s/, their category boundaries had shifted; hearing -rul led to expanded /f/ categories, -nud expanded /s/. Thus phonotactic sequence information alone induces perceptual retuning of phoneme category boundaries; lexical access is not required.

Abstract

A Bayesian model of continuous speech recognition is presented. It is based on Shortlist ( D. Norris, 1994; D. Norris, J. M. McQueen, A. Cutler, & S. Butterfield, 1997) and shares many of its key assumptions: parallel competitive evaluation of multiple lexical hypotheses, phonologically abstract prelexical and lexical representations, a feedforward architecture with no online feedback, and a lexical segmentation algorithm based on the viability of chunks of the input as possible words. Shortlist B is radically different from its predecessor in two respects. First, whereas Shortlist was a connectionist model based on interactive-activation principles, Shortlist B is based on Bayesian principles. Second, the input to Shortlist B is no longer a sequence of discrete phonemes; it is a sequence of multiple phoneme probabilities over 3 time slices per segment, derived from the performance of listeners in a large-scale gating study. Simulations are presented showing that the model can account for key findings: data on the segmentation of continuous speech, word frequency effects, the effects of mispronunciations on word recognition, and evidence on lexical involvement in phonemic decision making. The success of Shortlist B suggests that listeners make optimal Bayesian decisions during spoken-word recognition.

Abstract

Dutch listeners' looks to printed words were tracked while they listened to instructions to click with their mouse on one of them. When presented with targets from word pairs where the first two syllables were segmentally identical but differed in stress location, listeners used stress information to recognize the target before segmental information disambiguated the words. Furthermore, the amount of lexical competition was influenced by the presence or absence of word-initial stress.

Abstract

Segmental as well as suprasegmental information is used by Dutch listeners to recognize words. The time-course of the effect of suprasegmental stress information on spoken-word recognition was investigated in a previous study, in which we tracked Dutch listeners' looks to arrays of four printed words as they listened to spoken sentences. Each target was displayed along with a competitor that did not differ segmentally in its first two syllables but differed in stress placement (e.g., 'CENtimeter' and 'sentiMENT'). The listeners' eye-movements showed that stress information is used to recognize the target before distinct segmental information is available. Here, we examine the role of durational information in this effect. Two experiments showed that initial-syllable duration, as a cue to lexical stress, is not interpreted dependent on the speaking rate of the preceding carrier sentence. This still held when other stress cues like pitch and amplitude were removed. Rather, the speaking rate of the preceding carrier affected the speed of word recognition globally, even though the rate of the target itself was not altered. Stress information modulated lexical competition, but did so independently of the rate of the preceding carrier, even if duration was the only stress cue present.

Abstract

This study aimed first to determine whether there is a delay associated with processing words in an unfamiliar regional accent compared to words in a familiar regional accent, and second to establish whether short-term exposure to an unfamiliar accent affects the speed and accuracy of comprehension of words spoken in that accent. Listeners performed an animacy decision task for words spoken in their own and in an unfamiliar accent. Next, they were exposed to approximately 20 minutes of speech in one of these two accents. After exposure, they repeated the animacy decision task. Results showed a considerable delay in word processing for the unfamiliar accent, but no effect of short-term exposure.

Abstract

We present results from an experiment which shows that voice perception is influenced by the phonetic content of speech. Dutch listeners were presented with thirteen speakers pronouncing CVC words with systematically varying segmental content, and they had to discriminate the speakers’ voices. Results show that certain segments help listeners discriminate voices more than other segments do. Voice information can be extracted from every segmental position of a monosyllabic word and is processed rapidly. We also show that although relative discriminability within a closed set of voices appears to be a stable property of a voice, it is also influenced by segmental cues – that is, perceived uniqueness of a voice depends on what that voice says.

Abstract

We explore the role of the acoustic consequences of domain-initial strengthening in spoken-word recognition. In two cross-modal identity-priming experiments, listeners heard sentences and made lexical decisions to visual targets, presented at the onset of the second word in two-word sequences containing lexical ambiguities (e.g., bus tickets, with the competitor bust). These sequences contained Intonational Phrase (IP) or Prosodic Word (Wd) boundaries, and the second word's initial Consonant and Vowel (CV, e.g., [tI]) was spliced from another token of the sequence in IP- or Wd-initial position. Acoustic analyses showed that IP-initial consonants were articulated more strongly than Wd-initial consonants. In Experiment 1, related targets were post-boundary words (e.g., tickets). No strengthening effect was observed (i.e., identity priming effects did not vary across splicing conditions). In Experiment 2, related targets were pre-boundary words (e.g., bus). There was a strengthening effect (stronger priming when the post-boundary CVs were spliced from IP-initial than from Wd-initial position), but only in Wd-boundary contexts. These were the conditions where phonetic detail associated with domain-initial strengthening could assist listeners most in lexical disambiguation. We discuss how speakers may strengthen domain-initial segments during production and how listeners may use the resulting acoustic correlates of prosodic strengthening during word recognition.

Abstract

Experiments 1 and 2 examined the time-course of retrieval of phonological, visual-shape and semantic knowledge as Dutch participants listened to sentences and looked at displays of four pictures. Given a sentence with beker, `beaker', for example, the display contained phonological (a beaver, bever), shape (a bobbin, klos), and semantic (a fork, vork) competitors. When the display appeared at sentence onset, fixations to phonological competitors preceded fixations to shape and semantic competitors. When display onset was 200 ms before (e.g.) beker, fixations were directed to shape and then semantic competitors, but not phonological competitors. In Experiments 3 and 4, displays contained the printed names of the previously-pictured entities; only phonological competitors were fixated preferentially. These findings suggest that retrieval of phonological, shape and semantic knowledge in the spoken-word and picture-recognition systems is cascaded, and that visual attention shifts are co-determined by the time-course of retrieval of all three knowledge types and by the nature of the information in the visual environment.

Abstract

Listeners use lexical knowledge to adjust their prelexical representations of speech sounds in response to the idiosyncratic pronunciations of particular speakers. We used an exposure-test paradigm to investigate whether this type of perceptual learning transfers across syllabic positions. No significant learning effect was found in Experiment 1, where exposure sounds were onsets and test sounds were codas. Experiments 2-4 showed that there was no learning even when both exposure and test sounds were onsets. But a trend was found when exposure sounds were codas and test sounds were onsets (Experiment 5). This trend was smaller than the robust effect previously found for the coda-to-coda case. These findings suggest that knowledge about idiosyncratic pronunciations may be position specific: Knowledge about how a speaker produces sounds in one position, if it can be acquired at all, influences perception of sounds in that position more strongly than of sounds in another position.

Abstract

Words repeated in the same voice are better recognized than when they are repeated in a different voice. Such findings have been taken as evidence for the storage of talker-specific lexical episodes. But results on perceptual learning suggest that talker-specific adjustments concern sublexical representations. This study thus investigates whether voice-specific repetition effects in auditory lexical decision are lexical or sublexical. The same critical set of items in Block 2 were, depending on materials in Block 1, either same-voice or different-voice word repetitions, new words comprising re-orderings of phonemes used in the same voice in Block 1, or new words with previously unused phonemes. Results show a benefit for words repeated by the same talker, and a smaller benefit for words consisting of phonemes repeated by the same talker. Talker-specific information thus appears to influence word recognition at multiple representational levels.

Abstract

Listeners use suprasegmental auditory lexical stress information to resolve the competition words engage in during spoken-word recognition. The present study investigated whether (a) visual speech provides lexical stress information, and, more importantly, (b) whether this visual lexical stress information is used to resolve lexical competition. Dutch word pairs that differ in the lexical stress realization of their first two syllables, but not segmentally (e.g., 'OCtopus' and 'okTOber'; capitals marking primary stress) served as auditory-only, visual-only, and audiovisual speech primes. These primes either matched (e.g., 'OCto-'), mismatched (e.g., 'okTO-'), or were unrelated to (e.g., 'maCHI-') a subsequent printed target (octopus), which participants had to make a lexical decision to. To the degree that visual speech contains lexical stress information, lexical decisions to printed targets should be modulated through the addition of visual speech. Results show, however, no evidence for a role of visual lexical stress information in audiovisual spoken-word recognition.

Abstract

Eye movements of Dutch participants were tracked as they looked at arrays of four words on a computer screen and followed spoken instructions (e.g., "Klik op het woord buffel": Click on the word buffalo). The arrays included the target (e.g., buffel), a phonological competitor (e.g., buffer, buffer), and two unrelated distractors. Targets were monosyllabic or bisyllabic, and competitors mismatched targets only on either their onset or offset phoneme and only by one distinctive feature. Participants looked at competitors more than at distractors, but this effect was much stronger for offset-mismatch than onset-mismatch competitors. Fixations to competitors started to decrease as soon as phonetic evidence disfavouring those competitors could influence behaviour. These results confirm that listeners continuously update their interpretation of words as the evidence in the speech signal unfolds and hence establish the viability of the methodology of using eye movements to arrays of printed words to track spoken-word recognition.

Abstract

This chapter is a review of the literature in experimental psycholinguistics on spoken word recognition. It is organized around eight questions. 1. Why are psycholinguists interested in spoken word recognition? 2. What information in the speech signal is used in word recognition? 3. Where are the words in the continuous speech stream? 4. Which words did the speaker intend? 5. When, as the speech signal unfolds over time, are the phonological forms of words recognized? 6. How are words recognized? 7. Whither spoken word recognition? 8. Who are the researchers in the field?

Abstract

We investigated perception of words with reduced word-final /t/ using an adapted eyetracking paradigm. Dutch listeners followed spoken instructions to click on printed words which were accompanied on a computer screen by simple shapes (e.g., a circle). Targets were either above or next to their shapes, and the shapes uniquely identified the targets when the spoken forms were ambiguous between words with or without final /t/ (e.g., bult, bump, vs. bul, diploma). Analysis of listeners’ eye-movements revealed, in contrast to earlier results, that listeners use the following segmental context when compensating for /t/-reduction. Reflecting that /t/-reduction is more likely to occur before bilabials, listeners were more likely to look at the /t/-final words if the next word’s first segment was bilabial. This result supports models of speech perception in which prelexical phonological processes use segmental context to modulate word recognition.

Abstract

Listeners can make perceptual adjustments to phoneme categories in response to a talker who consistently produces a specific phoneme ambiguously. We investigate here whether this type of perceptual learning is also used to adapt to regional accent differences. Listeners were exposed to words produced by a Flemish talker whose realization of [x℄or [h℄ was ambiguous (producing [x℄like [h℄is a property of the West-Flanders regional accent). Before and after exposure they categorized a [x℄-[h℄continuum. For both Dutch and Flemish listeners there was no shift of the categorization boundary after exposure to ambiguous sounds in [x℄- or [h℄-biasing contexts. The absence of a lexically-driven learning effect for this contrast may be because [h℄is strongly influenced by coarticulation. As is not stable across contexts, it may be futile to adapt its representation when new realizations are heard

Abstract

We investigated how listeners of two unrelated languages, Korean and Dutch, process phonologically viable and nonviable consonants spoken in Dutch and American English. To Korean listeners, released final stops are nonviable because word-final stops in Korean are never released in words spoken in isolation, but to Dutch listeners, unreleased word-final stops are nonviable because word-final stops in Dutch are generally released in words spoken in isolation. Two phoneme monitoring experiments showed a phonological effect on both Dutch and English stimuli: Korean listeners detected the unreleased stops more rapidly whereas Dutch listeners detected the released stops more rapidly and/or more accurately. The Koreans, however, detected released stops more accurately than unreleased stops, but only in the non-native language they were familiar with (English). The results suggest that, in non-native speech perception, phonological legitimacy in the native language can be more important than the richness of phonetic information, though familiarity with phonetic detail in the non-native language can also improve listening performance.

Abstract

Perceptual representations of phonemes are flexible and adapt rapidly to accommodate idiosyncratic articulation in the speech of a particular talker. This letter addresses whether such adjustments remain stable over time and under exposure to other talkers. During exposure to a story, listeners learned to interpret an ambiguous sound as [f] or [s]. Perceptual adjustments measured after 12 h were as robust as those measured immediately after learning. Equivalent effects were found when listeners heard speech from other talkers in the 12 h interval, and when they had the opportunity to consolidate learning during sleep.

Abstract

A perceptual learning experiment provides evidence that the mental lexicon cannot consist solely of detailed acoustic traces of recognition episodes. In a training lexical decision phase, listeners heard an ambiguous [f–s] fricative sound, replacing either [f] or [s] in words. In a test phase, listeners then made lexical decisions to visual targets following auditory primes. Critical materials were minimal pairs that could be a word with either [f] or [s] (cf. English knife–nice), none of which had been heard in training. Listeners interpreted the minimal pair words differently in the second phase according to the training received in the first phase. Therefore, lexically mediated retuning of phoneme perception not only influences categorical decisions about fricatives (Norris, McQueen, & Cutler, 2003), but also benefits recognition of words outside the training set. The observed generalization across words suggests that this retuning occurs prelexically. Therefore, lexical processing involves sublexical phonological abstraction, not only accumulation of acoustic episodes.

Abstract

The speech perception system must be flexible in responding to the variability in speech sounds caused by differences among speakers and by language change over the lifespan of the listener. Indeed, listeners use lexical knowledge to retune perception of novel speech (Norris, McQueen, & Cutler, 2003). In that study, Dutch listeners made lexical decisions to spoken stimuli, including words with an ambiguous fricative (between [f] and [s]), in either [f]- or [s]-biased lexical contexts. In a subsequent categorization test, the former group of listeners identified more sounds on an [εf] - [εs] continuum as [f] than the latter group. In the present experiment, listeners received the same exposure and test stimuli, but did not make lexical decisions to the exposure items. Instead, they counted them. Categorization results were indistinguishable from those obtained earlier. These adjustments in fricative perception therefore do not depend on explicit judgments during exposure. This learning effect thus reflects automatic retuning of the interpretation of acoustic-phonetic information.

Abstract

We propose that speech comprehension involves the activation of token representations of the phonological forms of current lexical hypotheses, separately from the ongoing construction of a conceptual interpretation of the current utterance. In a series of cross-modal priming experiments, facilitation of lexical decision responses to visual target words (e.g., time) was found for targets that were semantic associates of auditory prime words (e.g., date) when the primes were isolated words, but not when the same primes appeared in sentence contexts. Identity priming (e.g., faster lexical decisions to visual date after spoken date than after an unrelated prime) appeared, however, both with isolated primes and with primes in prosodically neutral sentences. Associative priming in sentence contexts only emerged when sentence prosody involved contrastive accents, or when sentences were terminated immediately after the prime. Associative priming is therefore not an automatic consequence of speech processing. In no experiment was there associative priming from embedded words (e.g., sedate-time), but there was inhibitory identity priming (e.g., sedate-date) from embedded primes in sentence contexts. Speech comprehension therefore appears to involve separate distinct activation both of token phonological word representations and of conceptual word representations. Furthermore, both of these types of representation are distinct from the long-term memory representations of word form and meaning.

Abstract

Participants made visual lexical decisions to upper-case words and nonwords, and then categorized an ambiguous N–H letter continuum. The lexical decision phase included different exposure conditions: Some participants saw an ambiguous letter “?”, midway between N and H, in N-biased lexical contexts (e.g., REIG?), plus words with unambiguousH(e.g., WEIGH); others saw the reverse (e.g., WEIG?, REIGN). The first group categorized more of the test continuum as N than did the second group. Control groups, who saw “?” in nonword contexts (e.g., SMIG?), plus either of the unambiguous word sets (e.g., WEIGH or REIGN), showed no such subsequent effects. Perceptual learning about ambiguous letters therefore appears to be based on lexical knowledge, just as in an analogous speech experiment (Norris, McQueen, & Cutler, 2003) which showed similar lexical influence in learning about ambiguous phonemes. We argue that lexically guided learning is an efficient general strategy available for exploitation by different specific perceptual tasks.

Abstract

In two eye-tracking experiments, we examined the degree to which listeners use acoustic cues to word boundaries. Dutch participants listened to ambiguous sentences in which stop-initial words (e.g., pot, jar) were preceded by eens (once); the sentences could thus also refer to cluster-initial words (e.g., een spot, a spotlight). The participants made fewer fixations to target pictures (e.g., a jar) when the target and the preceding [s] were replaced by a recording of the cluster-initial word than when they were spliced from another token of the target-bearing sentence (Experiment 1). Although acoustic analyses revealed several differences between the two recordings, only [s] duration correlated with the participants’ fixations (more target fixations for shorter [s]s). Thus, we found that listeners apparently do not use all available acoustic differences equally. In Experiment 2, the participants made more fixations to target pictures when the [s] was shortened than when it was lengthened. Utterance interpretation can therefore be influenced by individual segment duration alone.

Abstract

An eye-tracking study examined the involvement of prosodic knowledge—specifically, the knowledge that monosyllabic words tend to have longer durations than the first syllables of polysyllabic words—in the recognition of newly learned words. Participants learned new spoken words (by associating them to novel shapes): bisyllables and onset-embedded monosyllabic competitors (e.g., baptoe and bap). In the learning phase, the duration of the ambiguous sequence (e.g., bap) was held constant. In the test phase, its duration was longer than, shorter than, or equal to its learning-phase duration. Listeners’ fixations indicated that short syllables tended to be interpreted as the first syllables of the bisyllables, whereas long syllables generated more monosyllabic-word interpretations. Recognition of newly acquired words is influenced by prior prosodic knowledge and is therefore not determined solely on the basis of stored episodes of those words.

Abstract

In an eye-tracking study, we examined how fine-grained phonetic detail, such as segment duration, influences the lexical competition process during spoken word recognition. Dutch listeners’ eye movements to pictures of four objects were monitored as they heard sentences in which a stop-initial target word (e.g., pijp “pipe”) was preceded by an [s]. The participants made more fixations to pictures of cluster-initial words (e.g., spijker “nail”) when they heard a long [s] (mean duration, 103 msec) than when they heard a short [s] (mean duration, 73 msec). Conversely, the participants made more fixations to pictures of the stop-initial words when they heard a short [s] than when they heard a long [s]. Lexical competition between stop- and cluster-initial words, therefore, is modulated by segment duration differences of only 30 msec.

Abstract

Effects on spoken-word recognition of prevoicing differences in Dutch initial voiced plosives were examined. In 2 cross-modal identity-priming experiments, participants heard prime words and nonwords beginning with voiced plosives with 12, 6, or 0 periods of prevoicing or matched items beginning with voiceless plosives and made lexical decisions to visual tokens of those items. Six-period primes had the same effect as 12-period primes. Zero-period primes had a different effect, but only when their voiceless counterparts were real words. Listeners could nevertheless discriminate the 6-period primes from the 12- and 0-period primes. Phonetic detail appears to influence lexical access only to the extent that it is useful: In Dutch, presence versus absence of prevoicing is more informative than amount of prevoicing.