Robert R. Verbrugge

An effect of linguistic experience: The discrimination of [r] and [l] by native speakers of Japanese and English

To test the effect of linguistic experience on the perception of a cue that is known to be effective in distinguishing between [r] and [l] in English, 21 Japanese and 39 American adults were tested on discrimination of a set of synthetic speech-like stimuli. The 13 “speech” stimuli in this set varied in the initial stationary frequency of the third formant (F3) and its subsequent transition into the vowel over a range sufficient to produce the perception of [r a] and [l a] for American subjects and to produce [r a] (which is not in phonemic contrast to [l a ]) for Japanese subjects. Discrimination tests of a comparable set of stimuli consisting of the isolated F3 components provided a “nonspeech” control. For Americans, the discrimination of the speech stimuli was nearly categorical, i.e., comparison pairs which were identified as different phonemes were discriminated with high accuracy, while pairs which were identified as the same phoneme were discriminated relatively poorly. In comparison, discrimination of speech stimuli by Japanese subjects was only slightly better than chance for all comparison pairs. Performance on nonspeech stimuli, however, was virtually identical for Japanese and American subjects; both groups showed highly accurate discrimination of all comparison pairs. These results suggest that the effect of linguistic experience is specific to perception in the “speech mode.”

Linguistic and acoustic correlates of the perceptual structure found in an individual differences scaling study of vowels

Subjects judged the similarities among a set of American English vowels (See Text) presented in isolation or in a/dVd/ consonantal frame. Individual differences scaling was employed to analyze these similarities data for each of the conditions separately and for the two conditions combined. In all cases, perceptual dimensions corresponding to the advancement, height, and tenseness vowel features were recovered. Given the determinacy of individual differences scaling, this finding is taken to provide strong evidence for the perceptual significance of those features. The perceptual dimensions are considered in relation to various acoustic parameters of the stimuli employed in this study. They are also considered in relation to perceptual dimensions that have been observed in other vowel scaling studies.

Talker‐independent information for vowel identity

A male and a female talker each produced a set of /bVb/ syllables (V = /i,I,e,e,ae,a,ʌ,ɔ,o,ʋ,u/) at metronome‐controlled rates. The central 60% of the voiced regions of these syllables was edited out, producing single‐talker silent‐center syllables [cf. W. Strange, J. J. Jenkins, and T. R. Edman, J. Acoust. Soc. Am. 61, S39 (1977)]. Comparable “hybrid” silent‐center syllables were created by appending the final 20% of one talkers syllable to the initial 20% of the other talkers production of the same syllable, again with a 60% silent region intervening. Vowel identification errors were relatively low for both the single‐talker (22.4%) and the hybrid (27.0%) silent‐center syllables, though errors in each case exceeded those found for the original (unedited) syllables, though errors in each case exceeded those found for the original (unedited) syllables (9.3%). Hybrids were generally heard as coherent syllables from a single source; the error pattern for the hybrids could not be interpreted as a joint func...

Judging sine wave stimuli as speech and as nonspeech

Interest in the perceptual equivalence of “static” and “dynamic” stimuli spans both speech and nonspeech domains. Previous investigations of speech stimuli have shown that, given matched sets of three‐formant steady‐state vowels and vowels flanked by consonantal transitions, phonetic equivalence is not defined by equal position along the two continua [B. Lindblom and M. Studdert‐Kennedy, J. Acoust. Soc. Am. 42, 830–843 (1967)]. For judgments of relative pitch, on the other hand, ramp tones are judged to be nearly equivalent in pitch to steady‐state tones at their endpoint frequencies [P. T. Brady et al., J. Acoust. Soc. Am. 33, 1357–1362 (1961)]. The present set of experiments demonstrates this difference in categorization of static and dynamic stimuli using a single type of stimulus. Two sets of sine wave stimuli (FLAT/CONTOUR) were constructed by modeling the frequency and relative amplitude characteristics of the aforementioned speech stimuli. When judged in terms of phonetic categories (/ᴜ/ vs /ɪ/), s...

Context‐conditioned specification of vowel identity

Consonantal environment does not aid vowel identification universally, but preserves and sharpens the information for vowels differentially. In a vowel recognition task, listeners heard one of two test series: /pVp/ syllables or isolated vowels. The test items were spoken by a single male talker and contained a balanced distribution of the vowels /i, ɪ, e, ae, a, ɔ, ʌ, ᴜ, u/. During each block of 90 test trials, listeners targeted for one of the nine vowel types, checking “Yes” when they recognized an instance and “No” otherwise. For both misses and false alarms, there was a strong interaction between vowel type (close versus open) and context type (/pVp/ vs /V/). The open vowel pairs (/ɛ/ae/ , /ʌ/a/) showed consistently superior recognition in the /pVp/ consonantal environment; others did not. Asymmetries in confusion errors were observed for several vowel pairs in both environments. A dynamic articulatory model of the syllable can provide a parsimonious account for these effects. Listeners may be sensitiv...

Individual differences in the perception of isolated vowels and vowels in a consonantal context

Previous studies comparing the perception of isolated vowels with that of vowels produced in some consonantal context have generally focused on similarities and differences in the average performance of subjects in the two conditions. In this investigation, we wanted to look carefully at individual differences in vowel perception both within and between these conditions. We did so with the aid of a nonmetric individual differences scaling procedure developed by Takane et al. [Psychometrika 42, 7–67 (1977)]. The variance common to all subjects (in the two conditions combined) was modeled in a single multidimensional space, and the individual differences were represented as weights (or saliences) that each subject attached to the dimensions of the space. The data were similarity judgments collected (with the method of triadic comparisons) for a set of isolated vowels and for a set of vowels in context recorded by the same talker. The perceptual space had three dimensions. The first of these corresponded clo...

Shifts in vowel perception as a function of speaking rate

In rapid speech, acoustic analysis reveals that steady state vowel targets characteristically are not reached. Lindblom and Studdert‐Kennedy [J. Acoust. Soc. Am. 42, 830–843 (1967)] found in an experiment with synthetic speech that listeners showed a shift in the boundary between medial vowels /e/ and /U/ with variations in the rate and direction of formant transitions. Apparently, perceivers compensate for simulated articulatory undershoot by perceptual overshoot. An experiment with natural speech demonstrated shifts in the acoustic criteria listeners employed in vowel recognition as a function of perceived rate of utterance. Nine American English vowels in /p‐p/ environment were produced by a panel of 15 talkers in a fixed sentence frame. The unstressed, rapidly articulated /p‐p/ syllables were excised from the tape recording and assembled into listening tests. In one condition, the /p‐p/ targets were prefaced by three slowly articulated syllables /hi, ha, hu/. In the other test condition, no precursors...

Memory for isolated vowels and for vowels in a consonantal context: An individual differences scaling comparison

We have previously reported that an individual differences scaling comparison of the perception of isolated vowels and the perception of vowels in a consonantal environment (/dVd/) indicated the following: vowels are processed in a more linguistically appropriate way when they occur in consonantal context [B. Rakerd and R. R. Verbrugge, J. Acoust, Soc. Am. Suppl. 1 71, S76 (1982)]. In the present investigation, the method of that earlier experiment was extended to a study of vowel memory. Subjects were asked to make similarity judgments about their memories of (a) isolated vowels, or (b) vowels in /dVd/ consonantal context, and the resulting similarities matrices were submitted to nonmetric individual differences scaling. The scaling analysis indicated (1) that vowel memory, like vowel perception, is to a measurable degree organized around the features of advancement, height, and tenseness; and (2) that the previously reported perceptual influence of consonantal context is largely to be explained in terms...

Syllable stress and vowel identity

Variations in syllable stress create a constancy problem for vowel perception owing to the accompanying variations in formant structure. An earlier study [R. R. Verbrugge and D. P. Shankweiler, J. Acoust. Soc. Am. 61, 539 (1977)], failed to demonstrate perceptual “compensation” for stress changes, possibly because variation in the prosody of a carrier phrase was not effective in altering the perceived stress of the target syllables. In the present experiment, stress was varied by altering the acoustic structure of the target syllable itself. A male talker produced a set of carrier sentences containing either stressed or destressed /pVp/ syllables (V = /i, , e, ae, a, , , ν, u/). Two types of synthetic analogs were created using an OVE‐III synthesizer: (a) original formant analogs, matched in pitch, amplitude, duration, and formant frequencies to the original syllables, and (b) interchanged‐formant analogs, preserving the original prosody, but containing formants taken from the syllable of opposite stress. ...

On accounting for the poor recognition of isolated vowels

Earlier studies have shown that vowels spoken in isolation tend to be poorly perceived, even when they are produced by phonetically trained talkers. Listeners, however, generally make remarkably few errors in identification of vowels in CVC environment, even when each syllable is uttered by a different talker. Sets of nine American English vowels were spoken by a panel of talkers: in isolation and in a /p‐p/ environment. Measurements of the first three formant frequencies were obtained from spectrograms. Listening tests were made up by randomizing talkers and tokens, and these were presented to phonetically naive listeners. Percent recognition of the intended vowel (average over vowels) was 83% for the /p‐p/ condition and 58% for the isolated condition. When the formant frequencies of each talkers isolated and medial vowels are compared, the values are found to be highly similar. Another explanation must be sought for the perceptual difficulty of isolated steady‐state vowels.