Sensitivity to change in perception of speech

Abstract

Perceptual systems in all modalities are predominantly sensitive to stimulus change, and many examples of perceptual systems responding to change can be portrayed as instances of enhancing contrast. Multiple findings from perception experiments serve as evidence for spectral contrast explaining fundamental aspects of perception of coarticulated speech, and these findings are consistent with a broad array of known psychoacoustic and neurophysiological phenomena. Beyond coarticulation, important characteristics of speech perception that extend across broader spectral and temporal ranges may best be accounted for by the constant calibration of perceptual systems to maximize sensitivity to change. Sensorineural systems respond to changeIt is both true and fortunate that sensorineural systems respond to change and to little else. Perceptual systems do not record absolute level be it loudness, pitch, brightness, or color. This fact has been demonstrated in every sensory domain. Physiologically, sensory encoding is always relative. This sacrifice of absolute encoding has enormous benefits along the way to maximizing information transmission. Biological sensors have impressive dynamic range given their evolution via borrowed parts (e.g., gill arches becoming middle ear bones). However, biological dynamic range always is a small fraction of the physical range of absolute levels available in the environment as well as in the perceptual range essential to organisms' survival. This is true whether one is considering optical luminance or acoustic pressure. The beauty of sensory systems is that, by responding to relative change, a limited dynamic range adjusts to maximize the amount of change that can be detected in the environment.The simplest way that sensory systems adjust dynamic range to maximize sensitivity to change is via adaptation. Following nothing, a sensory stimulus triggers a strong sensation. However, when sustained sensory input does not change over time, constant stimulation loses impact. This sort of sensory attenuation due to adaptation is ubiquitous, and has been documented in vision (Riggs et al

Putting phonetic context effects into context: A commentary on Fowler (2006)

“…This principle can result in contrastive perception: for example, the F3 onset of a syllable will be perceived as lower in frequency, relative to neighboring high-frequency energy. Similar demonstrations of how spectral manipulations to sentence length speech contexts influence target speech identification have been made by a number of researchers (Kluender, Coady, & Kiefte, 2003;Ladefoged & Broadbent, 1957;Watkins & Makin, 1996). In each of these cases, the long-term spectral characteristics of the context phrase shifts perception of target speech stimuli in such a way that listeners are most likely to report hearing the speech sound with the spectrum most different from the precursor.…”

Cochlea-scaled entropy, not consonants, vowels, or time, best predicts speech intelligibility

“…Begin with the simple fact that a fundamental principle of perceptual systems is that they respond primarily to change (15). This fact has the formal consequence of increasing information transmission.…”

“…Data and analyses presented here support an informationtheoretic approach to speech perception (24,25). At the heart of this perspective lies the fundamental principle that perceptual systems respond primarily to change in the interest of maximizing transmission of new information (15). Results emphasize the importance of information (change), more than consonants, vowels, or time, for speech perception.…”

On the causes of compensation for coarticulation: Evidence for phonological mediation

“…Auditory accounts hold that context sensitivity is pervasive in perception in general (Kluender, Coady, & Kiefte, 2001;Warren, 1999) and that perceptual systems have evolved to cope with the lack of invariance in the environment. Lack of invariance in the environment is caused by, among other forces, inertia.…”