Publications

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.

Abstract

We investigated how listeners of two unrelated languages, Dutch and Korean, process phonotactically legitimate and illegitimate sounds spoken in Dutch and American English. To Dutch listeners, unreleased word-final stops are phonotactically illegal because word-final stops in Dutch are generally released in isolation, but to Korean listeners, released final stops are illegal because word-final stops are never released in Korean. Two phoneme monitoring experiments showed a phonotactic effect: Dutch listeners detected released stops more rapidly than unreleased stops whereas the reverse was true for Korean listeners. Korean listeners with English stimuli detected released stops more accurately than unreleased stops, however, suggesting that acoustic-phonetic cues associated with released stops improve detection accuracy. We propose that in non-native speech perception, phonotactic legitimacy in the native language speeds up phoneme recognition, the richness of acousticphonetic cues improves listening accuracy, and familiarity with the non-native language modulates the relative influence of these two factors.

Abstract

Several models of spoken word recognition postulate that recognition is achieved via a process of competition between lexical hypotheses. Competition not only provides a mechanism for isolated word recognition, it also assists in continuous speech recognition, since it offers a means of segmenting continuous input into individual words. We present statistics on the pattern of occurrence of words embedded in the polysyllabic words of the English vocabulary, showing that an overwhelming majority (84%) of polysyllables have shorter words embedded within them. Positional analyses show that these embeddings are most common at the onsets of the longer word. Although both phonological and syntactic constraints could rule out some embedded words, they do not remove the problem. Lexical competition provides a means of dealing with lexical embedding. It is also supported by a growing body of experimental evidence. We present results which indicate that competition operates both between word candidates that begin at the same point in the input and candidates that begin at different points (McQueen, Norris, & Cutler, 1994, Noms, McQueen, & Cutler, in press). We conclude that lexical competition is an essential component in models of continuous speech recognition.

Abstract

Spoken utterances contain few reliable cues to word boundaries, but listeners nonetheless experience little difficulty identifying words in continuous speech. The authors present data and simulations that suggest that this ability is best accounted for by a model of spoken-word recognition combining competition between alternative lexical candidates and sensitivity to prosodic structure. In a word-spotting experiment, stress pattern effects emerged most clearly when there were many competing lexical candidates for part of the input. Thus, competition between simultaneously active word candidates can modulate the size of prosodic effects, which suggests that spoken-word recognition must be sensitive both to prosodic structure and to the effects of competition. A version of the Shortlist model ( D. G. Norris, 1994b) incorporating the Metrical Segmentation Strategy ( A. Cutler & D. Norris, 1988) accurately simulates the results using a lexicon of more than 25,000 words.