What Are You Waiting For? Real‐Time Integration of Cues for Fricatives Suggests Encapsulated Auditory Memory

Abstract

Speech unfolds over time and the cues for even a single phoneme are rarely available simultaneously. Consequently, to recognize a single phoneme listeners must integrate material over several hundred milliseconds. Prior work contrasts two accounts: 1) a memory buffer account in which listeners accumulate auditory information in memory and only access higher level representations (i.e., lexical representations) when sufficient information has arrived; and 2) an immediate integration scheme in which lexical representations can be partially activated on the basis of early cues and then updated when more information arises. These studies have uniformly shown evidence for immediate integration for a variety of phonetic distinctions. We attempted to extend this to fricatives, a class of speech sounds which requires not only temporal integration of asynchronous cues (the frication, followed by the formant transitions 150–350 msec later), but also integration across different frequency bands, and compensation for contextual factors like coarticulation. Eye-movements in the visual world paradigm and showed clear evidence for a memory buffer. Results were replicated in five experiments, ruling out methodological factors and tying the release of the buffer to the onset of the vowel. These findings support a general auditory account for speech by suggesting that the acoustic nature of particular speech sounds may have large effects on how they are processed. It also has major implications for theories of auditory and speech perception by raising the possibility of a encapsulated memory buffers in early auditory processing.

Speech categorization develops slowly through adolescence.

“…After that, looks to the target increase, and competitors receive more looks than unrelated objects briefly. Fricatives (Panels D–F) showed more competition, and a slower timecourse than stops (Panels A–C), consistent with prior studies (Galle, 2014; Galle, Klein-Packard, Schreiber, & McMurray, submitted). A few developmental patterns are apparent (Supplement S4 for complete analyses).…”

“…We cannot assume that any phonetic contrast is representative of speech as a whole. Categorical perception, for example, is less robust in vowels (Fry, Abramson, Eimas, & Liberman, 1962) and fricatives (Healy & Repp, 1982), and fricatives may be integrated with other portions of the signal differently from other speech sounds (Galle et al, submitted; Ishida, Samuel, & Arai, 2016). Moreover, frequency differences among phonemes could contribute to the rate or robustness of their development (Thiessen & Pavlik, 2016).…”

The time‐course of speech perception revealed by temporally‐sensitive neural measures

“…Recently, researchers have used eye‐tracking tasks to investigate the extent to which gradient information is maintained over time (McMurray, Tanenhaus, & Aslin, 2009; Zellou & Dahan, 2019). Debate continues over the precise nature of these gradient representations, whether they are based on low‐level acoustic cues (Galle, Klein‐Packard, Schreiber, & McMurray, 2019) or gradient higher‐level representations (Brown‐Schmidt & Toscano, 2017; Falandays, Brown‐Schmidt, & Toscano, 2020). In either case, however, behavioral measures make it difficult to separate early perception from later categorization (Gerrits & Schouten, 2004; Schouten et al, 2003).…”

Now you hear me, later you don’t: The Immediacy of Linguistic Computation and the Representation of Speech

“…At a broader timescale, AOC clarifies the interpretation of listeners' sensitivity to withincategory acoustic variation. Past work showing that performance on memory tasks depends on acoustic clarity (Crowder & Morton, 1969;Frankish, 2008) or that sensitivity is maintained across syllables (Brown-Schmidt & Toscano, 2017;Falandays et al, 2020;McMurray et al, 2009), or integrated over a delay (Galle et al, 2019;Gwilliams et al, 2018), did not address the internal contents of the representations that support such sensitivity. The present findings provide direct evidence in favor of the position that gradience is maintained through probabilistic uncertainty about potential categories.…”