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

English listeners largely disregard suprasegmental cues to stress in recognizing words. Evidence for this includes the demonstration of Fear et al. [J. Acoust. Soc. Am. 97, 1893–1904 (1995)] that cross-splicings are tolerated between stressed and unstressed full vowels (e.g., au- of autumn, automata). Dutch listeners, however, do exploit suprasegmental stress cues in recognizing native-language words. In this study, Dutch listeners were presented with English materials from the study of Fear et al. Acceptability ratings by these listeners revealed sensitivity to suprasegmental mismatch, in particular, in replacements of unstressed full vowels by higher-stressed vowels, thus evincing greater sensitivity to prosodic goodness than had been shown by the original native listener group.

Abstract

Three experiments, in which Japanese listeners detected Japanese words embedded in nonsense sequences, examined the perceptual consequences of vowel devoicing in that language. Since vowelless sequences disrupt speech segmentation [Norris et al. (1997). Cognit. Psychol. 34, 191– 243], devoicing is potentially problematic for perception. Words in initial position in nonsense sequences were detected more easily when followed by a sequence containing a vowel than by a vowelless segment (with or without further context), and vowelless segments that were potential devoicing environments were no easier than those not allowing devoicing. Thus asa, “morning,” was easier in asau or asazu than in all of asap, asapdo, asaf, or asafte, despite the fact that the /f/ in the latter two is a possible realization of fu, with devoiced [u]. Japanese listeners thus do not treat devoicing contexts as if they always contain vowels. Words in final position in nonsense sequences, however, produced a different pattern: here, preceding vowelless contexts allowing devoicing impeded word detection less strongly (so, sake was detected less accurately, but not less rapidly, in nyaksake—possibly arising from nyakusake—than in nyagusake). This is consistent with listeners treating consonant sequences as potential realizations of parts of existing lexical candidates wherever possible.

Abstract

Recognizing word boundaries in continuous speech requires detailed knowledge of the native language. In the first year of life, infants acquire considerable word segmentation abilities. Infants at this early stage in word segmentation rely to a large extent on the metrical pattern of their native language, at least in stress-based languages. In Dutch and English (both languages with a preferred trochaic stress pattern), segmentation of strong-weak words develops rapidly between 7 and 10 months of age. Nevertheless, trochaic languages contain not only strong-weak words but also words with a weak-strong stress pattern. In this article, we present electrophysiological evidence of the beginnings of weak-strong word segmentation in Dutch 10-month-olds. At this age, the ability to combine different cues for efficient word segmentation does not yet seem to be completely developed. We provide evidence that Dutch infants still largely rely on strong syllables, even for the segmentation of weak-strong words.

Abstract

Two artificial-language learning experiments directly compared English, French, and Dutch listeners’ use of suprasegmental cues for continuous-speech segmentation. In both experiments, listeners heard unbroken sequences of consonant-vowel syllables, composed of recurring three- and four-syllable “words.” These words were demarcated by(a) no cue other than transitional probabilities induced by their recurrence, (b) a consistent left-edge cue, or (c) a consistent right-edge cue. Experiment 1 examined a vowel lengthening cue. All three listener groups benefited from this cue in right-edge position; none benefited from it in left-edge position. Experiment 2 examined a pitch-movement cue. English listeners used this cue in left-edge position, French listeners used it in right-edge position, and Dutch listeners used it in both positions. These findings are interpreted as evidence of both language-universal and language-specific effects. Final lengthening is a language-universal effect expressing a more general (non-linguistic) mechanism. Pitch movement expresses prominence which has characteristically different placements across languages: typically at right edges in French, but at left edges in English and Dutch. Finally, stress realization in English versus Dutch encourages greater attention to suprasegmental variation by Dutch than by English listeners, allowing Dutch listeners to benefit from an informative pitch-movement cue even in an uncharacteristic position.

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

The lexicon, considered as a component of the process of recognizing speech, is a device that accepts a sound image as input and outputs meaning. Lexical access is the process of formulating an appropriate input and mapping it onto an entry in the lexicon's store of sound images matched with their meanings. This chapter addresses the problems of auditory lexical access from continuous speech. The central argument to be proposed is that utterance prosody plays a crucial role in the access process. Continuous listening faces problems that are not present in visual recognition (reading) or in noncontinuous recognition (understanding isolated words). Aspects of utterance prosody offer a solution to these particular problems.

Abstract

The recent claim by Black and Byng (1986) that lexical access in reading is subject to prosodic constraints is examined and found to be unsupported. The evidence from impaired reading which Black and Byng report is based on poorly controlled stimulus materials and is inadequately analysed and reported. An alternative explanation of their findings is proposed, and new data are reported for which this alternative explanation can account but their model cannot. Finally, their proposal is shown to be theoretically unmotivated and in conflict with evidence from normal reading.

Abstract

The present experiment tested the suggestion that human listeners may exploit durational information in speech to parse continuous utterances into words. Listeners were presented with six-syllable unpredictable utterances under noise-masking, and were required to judge between alternative word strings as to which best matched the rhythm of the masked utterances. For each utterance there were four alternative strings: (a) an exact rhythmic and word boundary match, (b) a rhythmic mismatch, and (c) two utterances with the same rhythm as the masked utterance, but different word boundary locations. Listeners were clearly able to perceive the rhythm of the masked utterances: The rhythmic mismatch was chosen significantly less often than any other alternative. Within the three rhythmically matched alternatives, the exact match was chosen significantly more often than either word boundary mismatch. Thus, listeners both perceived speech rhythm and used durational cues effectively to locate the position of word boundaries.

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.

Abstract

An acoustically invariant one-word segment occurred in two versions of one syntactic context. In one version, the preceding intonation contour indicated that a stress would fall at the point where this word occurred. In the other version, the preceding contour predicted reduced stress at that point. Reaction time to the initial phoneme of the word was faster in the former case, despite the fact that no acoustic correlates of stress were present. It is concluded that a part of the sentence comprehension process is the prediction of upcoming sentence accents.