Reply to Matthei: we really is worse than you or them, and so are Ma and Pa.
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Humans↗
Biomedical subjects
A G Samuel
Publications and source records attributed to A G Samuel.
Perception of intervocalic stop consonants: the contributions of closure duration and formant transitions.
Acoustic analyses of vowel-consonant-vowel (VCV) utterances indicate that they generally include formant transitions from the first vowel into a period of closure (VC transitions), and transitions out of the closure into the second vowel (CV transitions). Three experiments investigated the perceptual importance of the VC transitions, the CV transitions, and the closure period in identification of medial stop consonants varying in place of articulation. Experiment 1 compared identification of members of synthetic VC and CV continua with those from VCV series made by concatenating corresponding VC and CV stimuli using various closure durations. Experiment 2 examined identification of VCV stimuli constructed with only VC, only CV, or both VC and CV transitions; again closure duration was systematically varied. Experiment 3 correlated CV and VC identification with identification of VCV stimuli. Neither closure duration nor formant transition structure (i.e., only VC, only CV, or both) had an independent effect on identification. Instead, the formant structure and closure duration together strongly affected stop identification. When both VC and CV transitions were present, the CV transitions contributed somewhat more to identification of medial stops with short closures, than the VC transitions did. With longer closure durations, neither set of transitions appeared to determine perceived place of articulation in any simple way. Overall, the data indicate that the perception of a medial consonant is more than simply a (weighted) sum of its parts.
Humans↗
Length effects in word perception: we is better than i but worse than you or them.
Under tachistoscopic viewing conditions letters are better reported if they are presented as part of a word than if they are presented in isolation. Several recent theories attribute this word advantage to the influence of lexical representations. The present study replicated Wheeler's finding that the words I and A do not have the same advantage as other words, despite their lexical status. This result holds even under conditions designed to influence subjects to process I and A as words. The poor performance on these single-letter words was shown to be a manifestation of a more general length effect: Recognition of briefly presented words improves with increasing length (up to three or four letters). The perceptual advantage for longer words was not found for closely matched strings of unrelated letters. The strength and robustness of the word-length effect suggest that theories of the word advantage must include mechanisms that are length dependent.
Adolescent↗
Phonetic prototypes.
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Adaptation, Physiological↗
The role of bottom-up confirmation in the phonemic restoration illusion.
Phonemic restoration is an illusion in which listeners hear spoken words as intact, even though parts of them have been replaced by an extraneous sound. An improved methodology was used to investigate how much the illusion depends upon the bottom-up confirmation of expectations generated at higher levels. A powerful bottom-up factor was phone class of the sound to be restored, and its acoustic similarity to the sound that replaced it. When white noise was the replacement sound, fricatives were better restored than vowels, whereas the pattern reversed with a pure tone replacement. Including a short silence period increased restoration of stop consonants. The data indicate that phonemic restoration depends upon the interplay between the listener's expectations and the acoustic signal.
Discrimination Learning↗
Phonemic restoration: insights from a new methodology.
Phonemic restoration is a powerful auditory illusion in which listeners "hear" parts of words that are not really there. In earlier studies of the illusion, segments of words (phonemes) were replaced by an extraneous sound; listeners were asked whether anything was missing and where the extraneous noise had occurred. Most listeners reported that the utterance was intact and mislocalized the noise, suggesting that they had restored the missing phoneme. In the present study, a second type of stimulus was also presented: items in which the extraneous sound was merely superimposed on the critical phoneme. On each trial, listeners were asked to report whether they thought a stimulus utterance was intact (noise superimposed) or not (noise replacing). Since this procedure yields both a miss rate P(intact/replaced), and a false alarm rate P(replaced/intact), signal detection parameters of discriminability and bias can be calculated. The discriminability parameter reflects how similar the two types of stimuli sound; perceptual restoration of replaced items should make them sound intact, producing low discriminability scores. The bias parameter measures the tendency of listeners to report utterances as intact; it reflects postperceptual decision processes. This improved methodology was used to test the hypothesis that restoration (and more generally, speech perception) depends upon the bottom-up confirmation of expectations generated at higher levels. Perceptual restoration varied greatly wih the phone class of the replaced segment and its acoustic similarity to the replacement sound, supporting a bottom-up component to the illusion. Increasing listeners' expectations of a phoneme increased perceptual restoration: missing segments in words were better restored than corresponding pieces in phonologically legal pseudowords; priming the words produced even more restoration. In contrast, sentential context affected the postperceptual decision stage, biasing listeners to report utterances as intact. A limited interactive model of speech perception, with both bottom-up and top-down components, is used to explain the results.
Attention↗
Adaptation of speech by nonspeech: evidence for complex acoustic cue detectors.
Three selective adaptation experiments were run, using nonspeech stimuli (music and noise) to adapt speech continua ([ba]-[wa] and [cha]-[sha]). The adaptors caused significant phoneme boundary shifts on the speech continua only when they matched in periodicity: Music stimuli adapted [ba]-[wa], whereas noise stimuli adapted [cha]-[sha]. However, such effects occurred even when the adaptors and test continua did not match in other simple acoustic cues (rise time or consonant duration). Spectral overlap of adaptors and test items was also found to be unnecessary for adaptation. The data support the existence of auditory processors sensitive to complex acoustic cues, as well as units that respond to more abstract properties. The latter are probably at a level previously thought to be phonetic. Asymmetrical adaptation was observed, arguing against an opponent-process arrangement of these units. A two-level acoustic model of the speech perception process is offered to account for the data.
Cues↗