Comprehension Dept Publications

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 study addresses the roles of segment deletion, durational reduction, and frequency of use in the comprehension of morphologically complex words. We report two auditory lexical decision experiments with reduced and unreduced prefixed Dutch words. We found that segment deletions as such delayed comprehension. Simultaneously, however, longer durations of the different parts of the words appeared to increase lexical competition, either from the word’s stem (Experiment 1) or from the word’s morphological continuation forms (Experiment 2). Increased lexical competition slowed down especially the comprehension of low frequency words, which shows that speakers do not try to meet listeners’ needs when they reduce especially high frequency words.

Abstract

The main goal of the present study is to trace the consequences of local and global markedness for the processing of singular and plural nouns. Decompositional models such as proposed by (Pinker (1997); Pinker (1999)) and (Levelt et al. (1999)) predict a lexeme frequency effect and no effects of the frequencies of the singular and the plural forms. Experiments 1 and 4 reveal the expected lexeme frequency effect. Furthermore, in these experiments there are no clear independent effects of the frequencies of the inflected forms. However, the effects of Entropy and Relative Entropy that emerge from these experiments show that in production knowledge of the probabilities of the individual inflected forms do play a role, albeit indirectly. These entropy effects bear witness to the importance of paradigmatic organization of inflected forms in the mental lexicon, both at the level of individual lexemes (Entropy) and at the general level of the class of nouns (Relative Entropy).

Abstract

To assess the reality of phonological features in language processing (vs. language description), one needs to specify the distinctive claims of distinctive-feature theory. Two of the more farreaching claims are compositionality and generalizability. I will argue that there is some evidence for the first and evidence against the second claim from a recent behavioral paradigm. Highlighting the contribution of a behavioral paradigm also counterpoints the use of brain measures as the only way to elucidate what is "real for the brain". The contributions of the speakers exemplify how brain measures can help us to understand the reality of phonological features in language processing. The evidence is, however, not convincing for a) the claim for underspecification of phonological features—which has to deal with counterevidence from behavioral as well as brain measures—, and b) the claim of position independence of phonological features.

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

This doctoral dissertation investigated the learning of auditory categories by applying insights from child language learning, visual category learning and phonetic categorization by adults. The experiments in chapter 2 concern supervised learning of multidimensional non-speech categories varying in two dimensions: duration and a non speech analogue of formant frequency. In experiment 1, one dimension of variation determined category membership, variation in the other dimension was irrelevant. Listeners quickly learned to categorize according to this distinction. In experiment 2, both dimensions needed to be combined to categorize correctly. Performance was much lower, but most listeners succeeded in this task. However, in a maintenance phase without feedback or distributional information, listeners reverted to a unidimensional solution. In a maintenance phase with distributional information, listeners did use both dimensions correctly, arguing for the importance of distributional information in (auditory) category acquisition. In chapter 3, the listeners had to classify the same categories, but without feedback. In experiment 1, listeners succeeded to discover the relevant dimension of variation (and ignore the irrelevant one) without feedback. Much of this learning was lost in the maintenance phase, especially for the dimension formant frequency. With two relevant dimensions (Experiment 2), listeners were not able to learn to use both dimensions and reverted to a unidimensional solution. Chapter 4 applied the paradigms of chapter 2 and 3 to the learning of speech categories. Spanish native listeners learned Dutch vowel contrast with one relevant dimension of variation. With feedback, learning was swift, although was not well maintained without feedback or distributional information. Without feedback, Spanish listeners reverted to the dimensions best known in their native phonology, formant frequency, even when distributional information pointed to duration. The results are discussed in chapter 5. The implications for models of speech acquisition are discussed.

Abstract

The difficulty of the task of segmenting a speech signal into its words is immediately clear when listening to a foreign language; it is much harder to segment the signal into its words, since the words of the language are unknown. Infants are faced with the same task when learning their first language. This study provides a better understanding of the task that infants face while learning their native language. We employed an automatic algorithm on the task of speech segmentation without prior knowledge of the labels of the phonemes. An analysis of the boundaries erroneously placed inside a phoneme showed that the algorithm consistently placed additional boundaries in phonemes in which acoustic changes occur. These acoustic changes may be as great as the transition from the closure to the burst of a plosive or as subtle as the formant transitions in low or back vowels. Moreover, we found that glottal vibration may attenuate the relevance of acoustic changes within obstruents. An interesting question for further research is how infants learn to overcome the natural tendency to segment these ‘dynamic’ phonemes.

Abstract

Early-acquired vocabulary is (of necessity) mostly based on auditory input. But for later-acquired vocabulary (in an L1 or L2), other knowledge sources can also be tapped. Where phonetic contrasts in an L2 cannot be adequately distinguished, the level of detail provided by these sources at the lexical level may be greater than prelexical processing is capable of matching.

Abstract

Four experiments examined whether Dutch listeners can learn to interpret a nonnative phoneme (English [\phontheta]) as an instance of a native category (Dutch [f] or [s]). During exposure in Experiment 1, two listener groups made lexical decisions to words and nonwords. Listeners heard [\phontheta] replacing [f] in 20 [f]-final words (Group 1), or [s] in 20 [s]-final words (Group 2). At test, participants heard e.g. [do\phontheta], based on the minimal pair doof/doos (deaf/box), and made visual lexical decisions to e.g. doof or doos. Group 1 were faster on doof decisions after [do\phontheta] than after an unrelated prime; Group 2 were faster on doos decisions. The groups had thus learned that [\phontheta] was, respectively, [f] or [s]. This learning was thorough: effects were just as large when the exposure sound was an ambiguous [fs]-mixture (Experiment 2) and when the test primes contained unambiguous [f] or [s] (Experiment 3). In Experiment 4, signal-correlated noise was used as the exposure sound. Listeners learned that the noise was an [f], irrespective of [f]- or [s]-biased exposure, showing that learning is determined by the new sound’s spectral characteristics. Perceptual learning in a native language is thorough, and can override years of second-language phonetic learning.

Abstract

We investigated whether non-native listeners can exploit phonetic detail in recognizing potentially ambiguous utterances, as native listeners can [6, 7, 8, 9, 10]. Due to the phenomenon of intrusive /r/, the English phrase extra ice may sound like extra rice. A production study indicates that the intrusive /r/ can be distinguished from the onset /r/ in rice, as it is phonetically weaker. In two cross-modal identity priming studies, however, we found no conclusive evidence that Dutch learners of English are able to make use of this difference. Instead, auditory primes such as extra rice and extra ice with onset and intrusive /r/s activate both types of targets such as ice and rice. This supports the notion of spurious lexical activation in L2 perception.

Abstract

Distributional learning is almost certainly involved in the human acquisition of phonetic categories. Because speech is inherently a multidimensional signal, learning phonetic categories entails multidimensional learning. Yet previous studies of auditory category learning have shown poor maintenance of learned multidimensional categories. Two experiments explored ways to improve maintenance: by increasing the costs associated with applying a unidimensional strategy; by providing additional information about the category structures; and by giving explicit instructions on how to categorize. Only with explicit instructions were categorization strategies maintained in a maintenance phase without supervision or distributional information.

Abstract

Dutch listeners outperform native listeners in identifying syllable stress in English. This is because lexical stress is more useful in recognition of spoken words of Dutch than of English, so that Dutch listeners pay greater attention to stress in general. We examined Dutch listeners’ use of the acoustic correlates of English stress. Primary- and secondary-stressed syllables differ significantly on acoustic measures, and some differences, in F0 especially, correlate with data of earlier listening experiments. The correlations found in the Dutch responses were not paralleled in data from native listeners. Thus the acoustic cues which distinguish English primary versus secondary stress are better exploited by Dutch than by native listeners.

Abstract

In this study, 1.5-year-olds were taught a novel word. Some children were familiarized with the word's phonological form before learning the word's meaning. Fidelity of phonological encoding was tested in a picture-fixation task using correctly pronounced and mispronounced stimuli. Only children with additional exposure in familiarization showed reduced recognition performance given slight mispronunciations relative to correct pronunciations; children with fewer exposures did not. Mathematical modeling of vocabulary exposure indicated that children may hear thousands of words frequently enough for accurate encoding. The results provide evidence compatible with partial failure of phonological encoding at 19 months of age, demonstrate that this limitation in learning does not always hinder word recognition, and show the value of infants' word-form encoding in early lexical development.

Abstract

Three 2AFC experiments investigated Dutch and English listeners’ use of preceding vowel duration for the English final /v/-/f/ contrast. Dutch listeners used vowel duration more flexibly than English listeners did: they could use vowel duration as accurately as native listeners, but were better at ignoring it when it was misleading.

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

In this study we investigated to what extent a meaningful sentence context facilitates spoken word processing in young and older listeners if listening is made taxing by time-compressing the speech. Even though elderly listeners have been shown to benefit more from sentence context in difficult listening conditions than young listeners, time compression of speech may interfere with semantic comprehension, particularly in older listeners because of cognitive slowing. The results of a target detection experiment showed that, unlike young listeners who showed facilitation by context at both rates, elderly listeners showed context facilitation at the intermediate, but not at the fastest rate. This suggests that semantic interpretation lags behind target identification.

Abstract

Two lexical decision experiments addressed the role of paradigmatic effects in auditory word recognition. Experiment 1 showed that listeners classified a form with an incorrectly voiced final obstruent more readily as a word if the obstruent is realised as voiced in other forms of that word's morphological paradigm. Moreover, if such was the case, the exact probability of paradigmatic voicing emerged as a significant predictor of the response latencies. A greater probability of voicing correlated with longer response latencies for words correctly realised with voiceless final obstruents. A similar effect of this probability was observed in Experiment 2 for words with completely voiceless or weakly voiced (incompletely neutralised) final obstruents. These data demonstrate the relevance of paradigmatically related complex words for the processing of morphologically simple words in auditory word recognition.