Perceptual Magnet Effect Research Articles

Neurophysiological correlates of the perceptual magnet effect in speech perception

This study investigated the Perceptual Magnet Effect (PME) in speech perception using behavioral and Event-Related Potentials (ERP) measures. There were two primary research questions: (1) whether category goodness rating influences speech discrimination with reduced sensitivity near the prototype and increased sensitivity in the vicinity of a poor exemplar, (2) whether the PME is domain-specific to speech sounds. Twenty adult native English speakers participated in identification, goodness rating, and discrimination tasks. The stimuli were synthesized vowels for /a/ and their nonspeech analogs by systematically varying the first two formants. ERP oddball conditions included four conditions presented in a counter-balanced order with the prototypical /a/ as the standard stimuli and its variants as deviants, and a non-prototypical /a/ as the standard and its variants as deviants, as well as the nonspeech matches. Results indicated that participants rated vowel category goodness based on the F2/F1 ratio for the /a/ sounds. Mismatch negativity amplitudes in the two speech conditions aligned with PME predictions, but similar patterns were also observed in the nonspeech conditions. The findings collectively demonstrated neurophysiological evidence for the perceptual organization of within-category variations in line with PME, which may transfer to auditory processing of similar acoustic patterns in nonspeech.

Internal structure of intonational categories: The (dis)appearance of a perceptual magnet effect.

The question of whether intonation events are speech categories like phonemes and lexical tones has long been a puzzle in prosodic research. In past work, researchers have studied categoricality of pitch accents and boundary tones by examining perceptual phenomena stemming from research on phoneme categories (i.e., intonation boundary effects-peaks in discrimination sensitivity at category boundaries, perceptual magnet effects-sensitivity minima near the best exemplar or prototype of a category). Both lines of research have yielded mixed results. However, boundary effects are not necessarily related to categoricality of speech. Using improved methodology, the present study examines whether pitch accents have domain-general internal structure of categories by testing the perceptual magnet effect. Perceived goodness and discriminability of re-synthesized productions of Dutch rising pitch accent (L*H) were evaluated by native speakers of Dutch in three experiments. The variation between these stimuli was quantified using a polynomial-parametric modeling approach. A perceptual magnet effect was detected: (1) rated "goodness" decreased as acoustic-perceptual distance relative to the prototype increased (Experiment 1), and (2) equally spaced items far from the prototype were more frequently discriminated than equally spaced items in the neighborhood of the prototype (Experiment 2). These results provide first evidence for internal structure of pitch accents, similar to that found in color and phoneme categories. However, the discrimination accuracy gathered here was lower than that reported for phonemes. The discrimination advantage in the neighborhood far from the prototype disappeared when participants were tested on a very large number of stimuli (Experiment 3), similar to findings on phonemes and different from findings for lexical tones in neutral network simulations of distributional learning. These results suggest a more transient nature of the perceptual magnet effect in the perception of pitch accents and arguably weaker categoricality of pitch accents, compared to that of phonemes and in particular of lexical tones.

A Narrative Review of Auditory Categorisation and Its Potential Role in Tinnitus Perception

Auditory categorisation is a phenomenon reflecting the non-linear nature of human perceptual spaces which govern sound perception. Categorisation training paradigms may reduce sensitivity toward training stimuli, decreasing the representation of these stimuli in auditory perceptual maps. Reduced cortical representation may have clinical implications for conditions that arise from disturbances in cortical activation, such as tinnitus. This review explores the categorisation of sound, with a particular focus on tinnitus. The potential of categorisation training as a sound-based tinnitus therapy is discussed. A narrative review methodological framework was followed. Four databases (PubMed, Google Scholar, Scopus, and ScienceDirect) were extensively searched for the following key words: categorisation, categorical perception, perceptual magnet effect, generalisation, and categorisation OR categorical perception OR perceptual magnet effect OR generalisation AND sound. Given the exploratory nature of the review and the fact that early works on categorisation are crucial to the understanding and development of auditory categorisation, all study types were selected for the period 1950–2022. Reference lists of articles were reviewed to identify any further relevant studies. The results of the review were catalogued and organised into themes. In total, 112 articles were reviewed in full, from which 59 were found to contain relevant information and were included in the review. Key themes identified included categorical perception of speech stimuli, warping of the auditory perceptual space, categorisation versus discrimination, the presence of categorisation across several modalities, and categorisation as an innate versus learned feature. Although a substantial amount of work focused on evaluating the effects of categorisation training on sound perception, only two studies investigated the effects of categorisation training on tinnitus. Implementation of a categorisation-based perceptual training paradigm could serve as a promising means of tinnitus management by reversing the changes in cortical plasticity that are seen in tinnitus, in turn altering the representation of sound within the auditory cortex itself. In the instance that the categorisation training is successful, this would likely mean a decrease in the level of activity within the auditory cortex (and other associated cortical areas found to be hyperactive in tinnitus) as well as a reduction in tinnitus salience.

Investigating the perceptual magnet effect in speech perception: An event-related potential study

The “Perceptual Magnet Effect” (PME) is characterized by perceptual warping in favor of stronger assimilation near the prototypical sound against other nonprotypical variants. This ERP study adopted a modified oddball paradigm to examine the PME predictions. The participants were 18 normal adults. The stimuli were computer-synthesized /a/ sounds and their acoustic controls by replacing the formant frequencies with sinewaves. Prior to the ERP sessions, the prototype (P) and nonprototype (NP) were chosen based on behavioral identification and goodness rating. Then 4 variants were created with ±40 mels apart in reference to P or NP, respectively, in either the first formant (F1) or second formant (F2). Mismatch negativity (MMN) responses were derived with the P (or NP) as the standard and the 4 variants as the deviant. The same ERP procedure was used for the nonspeech stimuli. Behavioral results showed that individual subjects consistently rated vowel category goodness based on the F2/F1 ratio. MMN amplitudes in the P and NP conditions showed a pattern consistent with the PME model. This pattern was observed for both speech and nonspeech stimuli. These results provide neural evidence in support of the PME that may extend to general auditory processing of spectral patterns.

A materialidade da língua em alguns aspectos da aquisição e da mudança (The materiality of language in some aspects of acquisition and change)

Neste artigo discute-se a aquisição e a mudança da língua como uma consequência da percepção de sua materialidade. Para isso, foram considerados os modelos da family resemblance e do perceptual magnet effect propostos por Elianor Rusch, a partir de Wittgenstein, e por Patricia Kuhl respectivamente, complementados pela hipótese do motherese como estímulo. Tais propostas foram tomadas como ponto de partida para a aquisição. A mudança, por sua vez, partiu dos modelos da Teoria Matemática da Comunicação, de Claude Shannon, tal como foi reformulado por Roman Jakobson e por Niklas Luhmann. Dados do Finlandês e do Alemão foram considerados como argumentos que justificassem a mudança do Latim para o Português como decorrência da percepção segundo os modelos propostos. Com base nesses argumentos, concluiu-se que a mudança decorreria de reações cumulativas, caracterizadas como aquisição pela formação inicial de formas prototípicas que sofreriam mudanças subsequentes conforme o sistema reaja aos estímulos externos.

Loanword adaptation: Phonological and cognitive issues

AbstractIn this paper, I focus on loanwords, and more specifically on the process known as loanword adaptation, namely the process by which a word’s original phonetics is altered to phonologically fit the borrowing language. More precisely, I seek to determine whether release bursts after the word-final coda in an English input might be responsible for final vowel epenthesis in the corresponding Korean output. To test this hypothesis, I compiled an original database listing English words that entered Korean until very recently. The analysis of that database actually supports the hypothesis. In a final conclusion, I discuss what this demonstration tells us about loanword adaptation and the process of borrowing from a psycholinguistic point of view. In particular, I emphasize the importance of both perception and native phonology in the process of loanword adaptation and conclude that Korean speakers seem indeed to be subject to the ‘perceptual magnet effect’, seeking (phonological) prototypes from various acoustic cues, and that so-called fine-grained phonetic detail has to be explored for a better understanding of phonological processes from a cognitive point of view.

Perceptual warping of phonetic space applies beyond known phonetic categories: Evidence from the perceptual magnet effect

What is the mental representation of phonetic space? Perceptual reorganization in infancy yields a reconfigured space “warped” around native-language (L1) categories. Is this reconfiguration entirely specific to L1 category inventory? Or does it apply to a broader range of category distinctions that are non-native, yet discriminable due to being defined by phonetic dimensions informative in the listener’s L1 (Bohn & Best, 2012; Pajak, 2012)? Here we address this question by studying perceptual magnets, which involve attrition of within-category distinctions and enhancement of distinctions across category boundaries (Kuhl, 1991). We focus on segmental length, known to yield L1-specific perceptual magnets: e.g., L1-Finnish listeners have one for [t]/[tt], but L1-Dutch listeners, who lack (exclusively) length-based contrasts, do not (Herren & Schouten, 2008). We tested 31 L1-Korean listeners in an AX discrimination task for [n]-[nn] and [f]-[ff] continua. Korean listeners have been shown to discriminate both (Pajak, 2012), despite only having the former set in the inventory. We found perceptual magnets for both continua, demonstrating that perceptual warping goes beyond the specific L1 categories: when a phonetic dimension is informative for contrasting some L1 categories, perceptual warping applies not only to the tokens from those categories, but also to that dimension more generally.

Simulation of neural mechanism for Chinese vowel perception with neural network model

Based on the results of psycholinguistic experiments, the perceptual magnet effect is the important factor in speech development. This effect produced a warped auditory space to the corresponding phoneme. The purpose of this study was to develop a neural network model in simulation of speech perception. The neural network model with unsupervised learning was used to determine the phonetic categories of phoneme according to the formant frequencies of the vowels. The modified self-organizing map (SOM) algorithm was proposed to produce the auditory perceptual space of English vowels. Simulated results were compared with findings from psycholinguistic experiments, such as categorization of English /r/ and /l/ and prototype and non-prototype vowels, to indicate the model’s ability to produce auditory perception space. In addition, this speech perception model was combined with the neural network model (Directions into Velocities Articulator, DIVA) to simulate categorization of ten English vowels and their productions to show the learning capability of speech perception and production. We further extended this modified DIVA model to show its capability to categorize six Chinese vowels (/a/, /i/, /u/, /e/, /o/, /y/) and their productions. Finally, this study proposed further development and related discussions for this speech perception model and its clinical application.

The influence of categories on perception: Explaining the perceptual magnet effect as optimal statistical inference.

A variety of studies have demonstrated that organizing stimuli into categories can affect the way the stimuli are perceived. We explore the influence of categories on perception through one such phenomenon, the perceptual magnet effect, in which discriminability between vowels is reduced near prototypical vowel sounds. We present a Bayesian model to explain why this reduced discriminability might occur: It arises as a consequence of optimally solving the statistical problem of perception in noise. In the optimal solution to this problem, listeners' perception is biased toward phonetic category means because they use knowledge of these categories to guide their inferences about speakers' target productions. Simulations show that model predictions closely correspond to previously published human data, and novel experimental results provide evidence for the predicted link between perceptual warping and noise. The model unifies several previous accounts of the perceptual magnet effect and provides a framework for exploring categorical effects in other domains.

Perceptual asymmetries induced by category learning

This paper takes an information-theoretic approach to study the perceptual consequences of the neural encoding of categories (e.g. vowels). We focus on two well-known psychophysical phenomena: categorical perception, characterized by greater cross-category than within-category discrimination, and perceptual magnet effect, stating that perceptual space is wrapped around prototypical instances of a given category, leading to a better ability to discriminate stimuli near non-prototypical exemplars of a category than near prototypical ones. Introducing a perceptual distance based on the Kullback-Leibler distance between the patterns of activity evoked by two stimuli, we show that both categorical perception and prototypical effects emerge from maximizing information contained in the neural representation about a set of categories. We discuss the relations between these two psychophysical phenomena and show that they go in hand with another kind of asymmetric effect. The discriminability between a category prototype and a non-prototype is not symmetric, depending on which stimuli serves as a referent. Non-prototypical stimuli are judged closer to prototypical exemplars than the reverse. Quantitative and qualitative comparisons with experimental data and previous theoretical work are presented and discussed.

The perceptual magnet effect (PME) in L2 consonants

The perceptual magnet effect (PME) has been investigated in conjunction with L1 vowels and consonants. However, there has been a paucity of examinations of the effect in L2 speech perception. The present study used the methodology of Iverson and Kuhl [P. Iverson and P. K. Kuhl, J. Acoust. Soc. Am. 99, 1130–1140 (1996)] to examine whether Japanese speakers who have had exposure to English-speaking environments for more than 1 year exhibit the PME for /r/ and /l/. Eighteen synthetic stimuli were generated. Ten Japanese speakers and 12 American English speakers participated in an identification and rating task. Each participant engaged in ten experimental sessions (ten sessions of each of the 18 stimuli). They chose either /ra/ or /la/ and gave a rating with a 1–7 scale. They also underwent a similarity scaling task to determine the similarity of 306 pairs of the 18 stimuli with a 1–7 scale. The results indicated that, while the English speakers demonstrated the PME, some native speakers of Japanese did exhibit the PME and prefer some exemplars of English /r/ and /l/ over others. The results also revealed that other Japanese speakers exhibited reorganized perceptual space without the PME.

Training effects on native and novel linguistic categories

Categorical perception (e.g., Liberman et al., 1957) and the perceptual magnet effect (Kuhl, 1991) are frequently invoked to help explain how the perceptual system deals with highly variable speech input by warping the perceptual system in favor of native contrasts. Research into L2 acquisition demonstrates that this warping can be overcome and non-native categories can be introduced to listeners with extensive training (e.g., Logan et al., 1991); further studies into novel category acquisition have shown a perceptual magnet effect for nonspeech stimuli (Guenther et al., 1999). This paper addresses native English speakers’ acquisition of a novel category, the velar fricative /x/, by testing the effects of category labeling and discrimination training on subjects sensory trace and context coding auditory modes. The results demonstrate training affects the novel category differently from the native categories, with labeling training creating a perceptual magnetlike effect only in the novel category. Both types of training increased subjects’ abilities to discriminate categories, but mixed testing and training types (i.e., categorical testing with noncategorical training and vice versa) resulted in the greatest improvements.

The perceptual magnet effect reflects phonetic context

Two experiments demonstrate that the perceptual magnet effect is context sensitive. In experiment 1a, 24 participants rated goodness of synthetic /u/ in isolation (ooh) and in two consonantal contexts, /lu/, /ju/ (Lou, you), with nine versions per word, varying in F2 frequency. Their most (prototypical) and least (nonprototypical) preferred choices reflected expected differences between words, and individual differences within words. Experiment 1b demonstrated standard perceptual magnet effects for prototype and nonprototype /u/ in the three words. Unlike previous work, each participant discriminated his/her own prototype and nonprototype from experiment 1a, rather than the group mean. Experiment 2a replicated 1a with 40 new participants. Experiment 2b compared discrimination around participants’ prototypical F2 frequency for /u/ in one word (original) with discrimination around that same frequency in another word (transferred). Different original/transferred sets were heard by four groups (ten participants each): /u/ and /lu/; /lu/ and /u/; /ju/ and /u/; /ju/ and /lu/. Discrimination (d′) near the prototype was poorer for original than transferred contexts [for the four comparisons, t(9) ranged between 2.43–3.49, p<0.025–0.005]. Thus, the perceptual magnet effect is syllable specific: the vowel prototype for one word need not generalize to another. Implications for perceptual coherence and phonological representation are discussed.

Neural activation during the discrimination of native and non-native speech contrasts by American and Japanese adults

Language experience influences speech perception in adults. Adult speakers have been shown to experience difficulty when discriminating non-native consonants that are not phonemic in the native phonetic repertoire. The present study examined behavioral and neural differences in the processes underlying the perception of native and non-native speech sounds. American-English and Japanese native-speaking adults participated in a functional magnetic resonance imaging (fMRI) study. The study focused on three consonants: the American English /r–l/ consonants and Japanese /r/. The investigation focused on neural correlates of both Kuhl’s perceptual magnet effect (PME) and the boundary effects typical of categorical perception (CP). Subjects performed in a behavioral task in which they identified provided goodness ratings, and discriminated stimuli varying in formants 2 and 3. Results will be discussed in relation to cortical activation patterns related to the PME and CP boundary effect for native and foreign language contrasts, and the effects of language experience on brain organization. [This work was supported by NIH grant (HD37954) and Talaris Institute.]

Effects of category learning on auditory perception and cortical maps

Our ability to discriminate sounds is not uniform throughout acoustic space. One example of auditory space warping, termed the perceptual magnet effect by Kuhl and colleagues, appears to arise from exposure to the phonemes of an infant’s native language. We have developed a neural model that accounts for the magnet effect in terms of neural map dynamics in auditory cortex. This model predicts that it should be possible to induce a magnet effect for non-speech stimuli. This prediction was verified by a psychophysical experiment in which subjects underwent categorization training involving non-speech auditory stimuli that were not categorical prior to training. The model further predicts that the magnet effect arises because prototypical vowels have a smaller cortical representation than non-prototypical vowels. This prediction was supported by an fMRI experiment involving prototypical and non-prototypical examples of the vowel /i/. Finally, the model predicts that categorization training with non-speech stimuli should lead to a decreased cortical representation for stimuli near the center of the category. This prediction was supported by an fMRI experiment involving categorization training with non-speech auditory stimuli. These results provide strong support for the model’s account of the effects of category learning on auditory perception and auditory cortical maps.

Learning sound categories: A neural model and supporting experiments.

Our ability to discriminate sounds such as vowels is not uniform throughout acoustic space. That is, our auditory perceptual spaces are warped representations of acoustic space. One example of auditory space warping, the perceptual magnet effect, arises from exposure to the phonemes of an infant’s native language. We have developed a neural model that accounts for this effect. The model is based on the idea that category learning during infancy changes the distribution of the firing preferences of neurons in auditory cortical maps and thus changes the discriminability of sounds from different parts of acoustic space. The model predicts that it should be possible to induce a perceptual magnet effect for non-speech stimuli. This prediction was verified by a psychophysical experiment in which subjects underwent categorization training involving non-speech auditory stimuli that were not “categorical” prior to training. The model further predicts that the magnet effect arises because prototypical vowels have smaller auditory cortical representations than non-prototypical vowels. This prediction was supported by a functional magnetic resonance imaging (fMRI) experiment involving prototypical and non-prototypical examples of the vowel /i/. The model thus provides an account of phoneme category learning that unifies observations from auditory psychophysics, cortical neurophysiology, and neural modeling.

A computational model for detecting and perceiving dynamic properities of speech

We investigate many aspects of a computational framework for detecting phonetically salient dynamic properties of the speech signal from continuous speech input. As a prototypical example of this problem, we consider frameworks for the detection of the transition from closure to burst for stop consonants in continuous speech. We formulate the problem as an optimal non-inear filtering problem. This involves the mapping of the dynamic acoustic data into a low dimension Riemannian manifold in an infinite dimensional Hilbert space. This leads to many kinds of metrics that can now be imposed on the dynamic speech signal and we explore these metrics in the context of the perceptual magnet effect. An extensive discussion of the robustness of the strategy, the nature of the errors made, the relationship to acoustic phonetis and distinctive features and to categorical perception will be conducted. Related problems that have a similar structure include nasal detection using transitions from vowels into adjacent nasals, transitional models of vowels and so on. Results of automatic speech recognition experiments using these dynamic features will be presented.

The Acoustics of Speech Communication: Fundamentals, Speech Perception Theory, and Technology

All chapters conclude with Summary. Preface. I.ACOUSTIC PHONETICS: SPEECH ENCODING FROM ARTICULATION TO SOUND STREAM. 1.Language, Phonetics, and Speech Production. Introduction: Language and Science. How Significant Is Acoustic Phonetics? Linguistics, Phonetics, and Phonology. General Conditions of Speech Production. Speech Sound Sources. 2.Sounds, Resonance, and Spectrum Analysis. Sound Production and Propagation. Simple Harmonic Motion. Definitions of Sine Wave Characteristics. Resonance. Definition of Resonant Frequency. Spectrum Analysis. Definitions of Spectrum Terms. Spectra of Recurring Resonant Oscillations. Definitions of Harmonics. Resonant Waves, Spectrum Plots, and Speech Waves. Aperiodic Speech Sounds. 3.Vowel Shaping and Vowel Formants. Model of Pharyngeal-Oral Tract. Spectrum of the Neutral Vowel [e]. Definition of Speech Formants. Vowel Formant Locations and Length of Pharyngeal-Oral Tract. Vocal Tract Constrictions and Formant Frequency Locations. Formants of Model Vowels. Central Vowels. 4.The Glottal Sound Source and the Spectra of Vowels. The Glottal Sound Source. The Phonation Mechanism. The Spectrum of the Glottal Sound Source. Source-Filter Theory of Vowel Production. Visualizing Speech Sounds. Anatomy of Spectrogram. Spectrograms of Vowels. Nasalization of Vowels. Phonemic Nasal Vowels. 5.Prosodic and Tonal Features. Introduction: Telling What and How. Parenting Speech. Prosodic Features of Language Forms. Glottal Source Factors in Stress and Intonation. Durational Prosodic Features. Oral Tract Shaping Factor. Intonation in Discourse. Pacing, Rhythm, and Languages. Tone Languages. 6.Consonant Features, Glides, and Stops. Articulatory Features of Consonants. Distinctive Features. Glide Consonants and Diphthongs. Glide and Voiced Stop. Glide and Stop at Middle Pace. Lateral and Retroflex Glides. Effects of Utterance Position. 7.Consonants: Nasal, Stop, and Fricative Manners of Articulation. Nasal Consonants. Nasal-Glide-Stop Differences. Fricative Consonants. 8.Consonants: The Voiced-Unvoiced Contrast. Production of the Voiced-Voiceless Distinction. Acoustics of Consonant Voicing. Voiced versus Unvoiced Final Consonants. Voiced and Unvoiced Fricatives. Physiological Studies of Consonant Voicing. Physiological Studies of Fricative Voicing. 9.Consonants: Features of Place of Articulation. Formant Transitions of Alveolar versus Labial Consonants. Consonant Place: Transition with Different Vowels. Place Features of Nasal Consonants. Place Features of Fricative Consonants. 10.The Flow of Speech. Coarticulation. Model of Speech Motor Programming. The Syllable as Coarticulation Unit. Effects of Rate of Utterance. Assimilation between Adjacent Consonants. II.SPEECH DECODING BY HUMAN AND MACHINE: FROM SOUND STREAM TO WORDS. 11.Acoustic Cues to Speech Perception, Winifred Strange. Perception of Steady-State Vowels. Speaker Normalization in Vowel Perception. Perception of Coarticulated Vowels. 12.Perception of Vowels: Dynamic Constancy, Winifred Strange. Boundaries of Consonant Categories. Categorical Perception of Speech Continua. Perception of Nonspeech Analogs. Integration of Acoustic Cues. Context and Rate Effects on Phonetic Category Boundaries. 13.Auditory Capacities and Phonological Development: Animal, Baby, and Foreign Listeners, Sarah Hawkins. Background: Does Phonological Perception Use Special Auditory Processes? Techniques for Studying Babies' Speech Perception. Categorical Perception by Babies. Speech Sound Classification by Babies: Prototype and the Perceptual Magnet Effect. Speech Sound Classification by Babies: Constancy. Speech Sound Discrimination by Animals. The Effect of Experience on Speech Sound Discrimination. Development Loss or Selective Attention? The Effect of Retraining. 14.Looking for Invariant Correlates of Linguistic Units: Two Classical Theories of Speech Perception, Sarah Hawkins. Defining the Task of Speech Perception. Overview of Acoustic-Phonetic Theories of Speech Perception. Introduction to Two Classical Theories of Speech Perception. The Motor Theory of Speech Perception. Acoustical Invariants: The Quantal Theory of Speech, Relational Acoustic Invariance, and Lexical Access from Features (LAFF). 15.Reevaluating Assumptions about Speech Perception: Interactive and Integrative Theories, Sarah Hawkins. What Have We Learned from the Classical Theories? Invariance in the Percept but Not the Object: The Theory of Direct Realism. A General Auditory Model without Acoustic Variance: Auditory Enhancement Theory. Categories of Sound? Toward a More Comprehensive Theory of Speech Perception. 16.Hearing Loss and the Audibility of Phoneme Cues, Sally G. Revoile. Consonant Acoustic-Cue Use by a Hypothetical Profoundly Hard of Hearing Person. Phoneme Acoustic-Cue Use by a Hypothetical Severely Hard of Hearing Person. Phoneme Acoustic-Cue Use by a Hypothetical Moderately Hard of Hearing Person. 17.Speech Technology. Speech Machines, J. M. Pickett & Juergen Schroeter. Speech Synthesis, Corine Bickley, Ann Syrdal, & Juergen Schroeter. Speech Recognition by Machine, Diane Kewley-Port. Appendixes. A: Experimenting with Speech. B: Sketches of Some Interesting Books for Phoneticians. References. Index.

Reply to “An analytical error invalidates the ‘depolarization’ of the perceptual magnet effect” [J. Acoust. Soc. Am. 107, 3576–3577 (2000)

In a previous paper, Lotto et al. [J. Acoust. Soc. Am. 103, 3648–3655 (1998)] claimed that experiments investigating a perceptual magnet effect (PME) failed to demonstrate a novel effect of goodness judgments on speech sound discrimination due to a confound in the procedure. New analyses of these data and a review of the recent literature fail once again to support the existence of PME.

The perceptual magnet effect in Australian English vowels.

Recent research (Kuhl, 1991) has suggested that the internal structure of vowel categories is graded in terms of stimulus goodness. It has been proposed that a best instance stimulus reflects a central point or prototype, which effectively renders within-category members perceptually more similar. Discrimination experiments suggest a nonlinear relationship between acoustic and perceptual space near category centers (Iverson & Kuhl, 1995b). This phenomenon has been described as the perceptual magnet effect. The present study investigated the presence of the perceptual magnet effect in five Australian vowel categories. Australian English speakers identified, rated, and discriminated between a pool of 32 vowel stimuli that varied in F1 and F2 values. The results from Experiments 1 and 2 showed that subjects were able to judge the quality and identify of each stimulus and that a general grading of stimulus quality was reported. This was not symmetrical, and the subjects' responses varied considerably. In Experiment 3, closer control of the methodology in the discrimination task and of contextual factors influencing the test materials was exercised. Despite this, evidence of the warping of perceptual space in discrimination data was not found. In general, these results do not provide support for the existence of the perceptual magnet effect, and explanations for this finding are discussed.