Publications

Abstract

Not only can the pitfalls that Firestone & Scholl (F&S) identify be generalised across multiple studies within the field of visual perception, but also they have general application outside the field wherever perceptual and cognitive processing are compared. We call attention to the widespread susceptibility of research on the perception of speech to versions of the same pitfalls.

Abstract

Speech perception involves prediction, but how is that prediction implemented? In cognitive models prediction has often been taken to imply that there is feedback of activation from lexical to pre-lexical processes as implemented in interactive-activation models (IAMs). We show that simple activation feedback does not actually improve speech recognition. However, other forms of feedback can be beneficial. In particular, feedback can enable the listener to adapt to changing input, and can potentially help the listener to recognise unusual input, or recognise speech in the presence of competing sounds. The common feature of these helpful forms of feedback is that they are all ways of optimising the performance of speech recognition using Bayesian inference. That is, listeners make predictions about speech because speech recognition is optimal in the sense captured in Bayesian models.

Abstract

Four cross-modal priming experiments and two forced-choice identification experiments investigated the use of suprasegmental cues to stress in the recognition of spoken English words, by native (English-speaking) and non- native (Dutch) listeners. Previous results had indicated that suprasegmental information was exploited in lexical access by Dutch but not by English listeners. For both listener groups, recognition of visually presented target words was faster, in comparison to a control condition, after stress-matching spoken primes, either monosyllabic (mus- from MUsic /muSEum) or bisyl labic (admi- from ADmiral/admiRAtion). For native listeners, the effect of stress-mismatching bisyllabic primes was not different from that of control primes, but mismatching monosyllabic primes produced partial facilitation. For non-native listeners, both bisyllabic and monosyllabic stress-mismatching primes produced partial facilitation. Native English listeners thus can exploit suprasegmental information in spoken-word recognition, but information from two syllables is used more effectively than information from one syllable. Dutch listeners are less proficient at using suprasegmental information in English than in their native language, but, as in their native language, use mono- and bisyllabic information to an equal extent. In forced-choice identification, Dutch listeners outperformed native listeners at correctly assigning a monosyllabic fragment (e.g., mus-) to one of two words differing in stress.

Abstract

Rhythmic categories such as morae in Japanese or stress units in English play a role in the perception of spoken
language. We examined this role in Japanese, since recent evidence suggests that morae may intervene as
structural units in word recognition. First, we found that traditional puns more often substituted part of a mora
than a whole mora. Second, when listeners reconstructed distorted words, e.g. panorama from panozema, responses
were faster and more accurate when only a phoneme was distorted (panozama, panorema) than when a
whole CV mora was distorted (panozema). Third, lexical decisions on the same nonwords were better predicted
by duration and number of phonemes from nonword uniqueness point to word end than by number of morae. Our
results indicate no role for morae in early spoken-word processing; we propose that rhythmic categories constrain
not initial lexical activation but subsequent processes of speech segmentation and selection among word candidates.

Abstract

Recognizing spoken language involves automatic activation of multiple candidate words. The process of selection between candidates is made more efficient by inhibition of embedded words (like egg in beg) that leave a portion of the input stranded (here, b). Results from European languages suggest that this inhibition occurs when consonants are stranded but not when syllables are stranded. The reason why leftover syllables do not lead to inhibition could be that in principle they might themselves be words; in European languages, a syllable can be a word. In Sesotho (a Bantu language), however, a single syllable cannot be a word. We report that in Sesotho, word recognition is inhibited by stranded consonants, but stranded monosyllables produce no more difficulty than stranded bisyllables (which could be Sesotho words). This finding suggests that the viability constraint which inhibits spurious embedded word candidates is not sensitive to language-specific word structure, but is universal.

Abstract

Becoming a native listener is the necessary precursor to becoming a native speaker. Babies in the first year of life undertake a remarkable amount of work; by the time they begin to speak, they have perceptually mastered the phonological repertoire and phoneme co-occurrence probabilities of the native language, and they can locate familiar word-forms in novel continuous-speech contexts. The skills acquired at this early stage form a necessary part of adult listening. However, the same native listening skills also underlie problems in listening to a late-acquired non-native language, accounting for why in such a case listening (an innate ability) is sometimes paradoxically more difficult than, for instance, reading (a learned ability).

Abstract

In four experiments, we examined the facilitation that occurs when spoken-word targets rhyme with preceding spoken primes. In Experiment 1, listeners’ lexical decisions were faster to words following rhyming words (e.g., ramp–LAMP) than to words following unrelated primes (e.g., pink–LAMP). No facilitation was observed for nonword targets. Targets that almost rhymed with their primes (foils; e.g., bulk–SULSH) were included in Experiment 2; facilitation for rhyming targets was severely attenuated. Experiments 3 and 4 were single-word shadowing variants of the earlier experiments. There was facilitation for both rhyming words and nonwords; the presence of foils had no significant influence on the priming effect. A major component of the facilitation in lexical decision appears to be strategic: Listeners are biased to say “yes” to targets that rhyme with their primes, unless foils discourage this strategy. The nonstrategic component of phonological facilitation may reflect speech perception processes that operate prior to lexical access.

Abstract

Spoken word recognition involves automatic activation of lexical candidates compatible with the perceived input. In running speech, words abut one another without intervening gaps, and syllable boundaries can mismatch with word boundaries. For instance, liaison in ’petit agneau’ creates a syllable beginning with a consonant although ’agneau’ begins with a vowel. In two cross-modal priming experiments we investigate how French listeners recognise words in liaison environments. These results suggest that the resolution of liaison in part depends on acoustic cues which distinguish liaison from non-liaison consonants, and in part on the availability of lexical support for a liaison interpretation.

Abstract

The recognition of speech involves the segmentation of continuous utterances into their component words. Cross-linguistic evidence is briefly reviewed which suggests that although there are language-specific solutions to this segmentation problem, they have one thing in common: they are all based on language rhythm. In English, segmentation is stress-based: strong syllables are postulated to be the onsets of words. Segmentation, however, can also be achieved by a process of competition between activated lexical hypotheses, as in the Shortlist model. A series of experiments is summarised showing that segmentation of continuous speech depends on both lexical competition and a metrically-guided procedure. In the final section, the implementation of metrical segmentation in the Shortlist model is described: the activation of lexical hypotheses matching strong syllables in the input is boosted and that of hypotheses mismatching strong syllables in the input is penalised.

Abstract

Japanese listeners detect speech sound targets which correspond precisely to a mora (a phonological unit which is the unit of rhythm in Japanese) more easily than targets which do not. English listeners detect medial vowel targets more slowly than consonants. Six phoneme detection experiments investigated these effects in both subject populations, presented with native- and foreign-language input. Japanese listeners produced faster and more accurate responses to moraic than to nonmoraic targets both in Japanese and, where possible, in English; English listeners responded differently. The detection disadvantage for medial vowels appeared with English listeners both in English and in Japanese; again, Japanese listeners responded differently. Some processing operations which listeners apply to speech input are language-specific; these language-specific procedures, appropriate for listening to input in the native language, may be applied to foreign-language input irrespective of whether they remain appropriate.

Abstract

Although word boundaries are rarely clearly marked, listeners can rapidly recognize the individual words of spoken sentences. Some theories explain this in terms of competition between multiply activated lexical hypotheses; others invoke sensitivity to prosodic structure. We describe a connectionist model, SHORTLIST, in which recognition by activation and competition is successful with a realistically sized lexicon. Three experiments are then reported in which listeners detected real words embedded in nonsense strings, some of which were themselves the onsets of longer words. Effects both of competition between words and of prosodic structure were observed, suggesting that activation and competition alone are not sufficient to explain word recognition in continuous speech. However, the results can be accounted for by a version of SHORTLIST that is sensitive to prosodic structure.

Abstract

Evidence is presented that (a) the open and the closed word classes in English have different phonological characteristics, (b) the phonological dimension on which they differ is one to which listeners are highly sensitive, and (c) spoken open- and closed-class words produce different patterns of results in some auditory recognition tasks. What implications might link these findings? Two recent lines of evidence from disparate paradigms—the learning of an artificial language, and natural and experimentally induced misperception of juncture—are summarized, both of which suggest that listeners are sensitive to the phonological reflections of open- vs. closed-class word status. Although these correlates cannot be strictly necessary for efficient processing, if they are present listeners exploit them in making word class assignments. That such a use of phonological information is of value to listeners could be indirect evidence that open- vs. closed-class words undergo different processing operations. Parts of the research reported in this paper were carried out in collaboration with Sally Butterfield and David Carter, and supported by the Alvey Directorate (United Kingdom). Jonathan Stankler's master's research was supported by the Science and Engineering Research Council (United Kingdom). Thanks to all of the above, and to Merrill Garrett, Mike Kelly, James McQueen, and Dennis Norris for further assistance.

Abstract

Cross-linguistic comparisons may shed light on the levels of processing involved in the performance of psycholinguistic tasks. For instance, if the same pattern of results appears whether or not subjects understand the experimental materials, it may be concluded that the results do not reflect higher-level linguistic processing. In the present study, English and French listeners performed two tasks - click location and speeded click detection - with both English and French sentences, closely matched for syntactic and phonological structure. Clicks were located more accurately in open- than in closed-class words in both English and French; they were detected more rapidly in open- than in closed-class words in English, but not in French. The two listener groups produced the same pattern of responses, suggesting that higher-level linguistic processing was not involved in the listeners' responses. It is concluded that click detection tasks are primarily sensitive to low-level (e.g. acoustic) effects, and hence are not well suited to the investigation of linguistic processing.

Abstract

The lexicon contains discrete entries, which must be located in speech input in order for speech to be understood; but the continuity of speech signals means that lexical access from spoken input involves a segmentation problem for listeners. The speech environment of prelinguistic infants may not provide special information to assist the infant listeners in solving this problem. Mature language users in possession of a lexicon might be thought to be able to avoid explicit segmentation of speech by relying on information from successful lexical access; however, evidence from adult perceptual studies indicates that listeners do use explicit segmentation procedures. These procedures differ across languages and seem to exploit language-specific rhythmic structure. Efficient as these procedures are, they may not have been developed in response to statistical properties of the input, because bilinguals, equally competent in two languages, apparently only possess one rhythmic segmentation procedure. The origin of rhythmic segmentation may therefore lie in the infant's exploitation of rhythm to solve the segmentation problem and gain a first toehold on lexical acquisition. Recent evidence from speech production and perception studies with prelinguistic infants supports the claim that infants are sensitive to rhythmic structure and its relationship to lexical segmentation.

Abstract

One critical aspect of language acquisition is the development of a lexicon that associates sounds and meanings; but developing a lexicon first requires that the infant segment utterances into individual words. How might the infant begin this process? The present study was designed to examine the potential role that sensitivity to predominant stress patterns of words might play in lexical development. In English, by far the majority of words have stressed (strong) initial syllables. Experiment 1 of our study demonstrated that by 9 months of age American infants listen significantly longer to words with strong/weak stress patterns than to words with weak/strong stress patterns. However, Experiment 2 showed that no significant preferences for the predominant stress pattern appear with 6-month-old infants, which suggests that the preference develops as a result of increasing familiarity with the prosodic features of the native language. In a third experiment, 9-month-olds showed a preference for strong/weak patterns even when the speech input was low-pass filtered, which suggests that their preference is specifically for the prosodic structure of the words. Together the results suggest that attention to predominant stress patterns in the native language may form an important part of the infant's process of developing a lexicon.

Abstract

On simple intelligibility measures, high-quality synthesiser output now scores almost as well as natural speech. Nevertheless, it is widely agreed that perception of synthetic speech is a harder task for listeners than perception of natural speech; in particular, it has been hypothesized that listeners have difficulty identifying phonemes in synthetic speech. If so, a simple measure of the speed with which a phoneme can be identified should prove a useful tool for comparing perception of synthetic and natural speech. The phoneme detection task was here used in three experiments comparing perception of natural and synthetic speech. In the first, response times to synthetic and natural targets were not significantly different, but in the second and third experiments response times to synthetic targets were significantly slower than to natural targets. A speed-accuracy tradeoff in the third experiment suggests that an important factor in this task is the response criterion adopted by subjects. It is concluded that the phoneme detection task is a useful tool for investigating phonetic processing of synthetic speech input, but subjects must be encouraged to adopt a response criterion which emphasizes rapid responding. When this is the case, significantly longer response times for synthetic targets can indicate a processing disadvantage for synthetic speech at an early level of phonetic analysis.

Abstract

Four experiments examined segmentation of spoken Japanese words by native and non-native listeners. Previous studies suggested that language rhythm determines the segmentation unit most natural to native listeners: French has syllabic rhythm, and French listeners use the syllable in segmentation, while English has stress rhythm, and segmentation by English listeners is based on stress. The rhythm of Japanese is based on a subsyllabic unit, the mora. In the present experiments Japanese listeners′ response patterns were consistent with moraic segmentation; acoustic artifacts could not have determined the results since nonnative (English and French) listeners showed different response patterns with the same materials. Predictions of a syllabic hypothesis were disconfirmed in the Japanese listeners′ results; in contrast, French listeners showed a pattern of responses consistent with the syllabic hypothesis. The results provide further evidence that listeners′ segmentation of spoken words relies on procedures determined by the characteristic phonology of their native language.

Abstract

Word-initial CVC syllables are detected faster in words beginning consonant-vowel-consonant-vowel (CVCV-) than in words beginning consonant-vowel-consonant-consonant (CVCC-). This effect was reported independently by M. Taft and G. Hambly (1985, Journal of Memory and Language, 24, 320–335) and by A. Cutler, J. Mehler, D. Norris, and J. Segui (1986, Journal of Memory and Language, 25, 385–400). Taft and Hambly explained the effect in terms of lexical factors. This explanation cannot account for Cutler et al.'s results, in which the effect also appeared with nonwords and foreign words. Cutler et al. suggested that CVCV-sequences might simply be easier to perceive than CVCC-sequences. The present study confirms this suggestion, and explains it as a reflection of listener expectations constructed on the basis of distributional characteristics of the language.

Abstract

Studies of human speech processing have provided evidence for a segmentation strategy in the perception of continuous speech, whereby a word boundary is postulated, and a lexical access procedure initiated, at each metrically strong syllable. The likely success of this strategy was here estimated against the characteristics of the English vocabulary. Two computerized dictionaries were found to list approximately three times as many words beginning with strong syllables (i.e. syllables containing a full vowel) as beginning with weak syllables (i.e. syllables containing a reduced vowel). Consideration of frequency of lexical word occurrence reveals that words beginning with strong syllables occur on average more often than words beginning with weak syllables. Together, these findings motivate an estimate for everyday speech recognition that approximately 85% of lexical words (i.e. excluding function words) will begin with strong syllables. This estimate was tested against a corpus of 190 000 words of spontaneous British English conversion. In this corpus, 90% of lexical words were found to begin with strong syllables. This suggests that a strategy of postulating word boundaries at the onset of strong syllables would have a high success rate in that few actual lexical word onsets would be missed.

Abstract

Infants acquire whatever language is spoken in the environment into which they are born. The mental capability of the newborn child is not biased in any way towards the acquisition of one human language rather than another. Because psychologists who attempt to model the process of language comprehension are interested in the structure of the human mind, rather than in the properties of individual languages, strategies which they incorporate in their models are presumed to be universal, not language-specific. In other words, strategies of comprehension are presumed to be characteristic of the human language processing system, rather than, say, the French, English, or Igbo language processing systems. We report here, however, on a comprehension strategy which appears to be used by native speakers of French but not by native speakers of English.

Abstract

Spontaneous self-corrections in speech pose a communication problem; the speaker must make clear to the listener not only that the original Utterance was faulty, but where it was faulty and how the fault is to be corrected. Prosodic marking of corrections - making the prosody of the repair noticeably different from that of the original utterance - offers a resource which the speaker can exploit to provide the listener with such information. A corpus of more than 400 spontaneous speech repairs was analysed, and the prosodic characteristics compared with the syntactic and semantic characteristics of each repair. Prosodic marking showed no relationship at all with the syntactic characteristics of repairs. Instead, marking was associated with certain semantic factors: repairs were marked when the original utterance had been actually erroneous, rather than simply less appropriate than the repair; and repairs tended to be marked more often when the set of items encompassing the error and the repair was small rather than when it was large. These findings lend further weight to the characterization of accent as essentially semantic in function.

Abstract

Two experiments examined the nature of access, storage, and comprehension of idiomatic phrases. In both studies a Phrase Classification Task was utilized. In this, reaction times to determine whether or not word strings constituted acceptable English phrases were measured. Classification times were significantly faster to idiom than to matched control phrases. This effect held under conditions involving different categories of idioms, different transitional probabilities among words in the phrases, and different levels of awareness of the presence of idioms in the materials. The data support a Lexical Representation Hypothesis for the processing of idioms.