Phonological features, auditory objects, and illusions

Abstract

It is argued that speech perception, just like visual perception, relies on a good match between memorized experience and current sensation: when sensation meshes with expectations, listeners believe they perceive ‘real’ linguistic objects in spite of possibly severe variation and degradation in the acoustic signal. Reviews of the acoustic and perceptual correlates of the features [nasal] and [voice] in various speech styles illustrate how multiple perceptual cues to a simple phonological distinction may be dispersed across syllables, and how absence of one or several such cues may be compensated by the presence of others, or by recovery processes that rely on listeners’ knowledge and expectations. Visual illusions are discussed which have apparent parallels with auditory illusions and with well-known aspects of speech perception. These include particular types of physical structure (e.g. abrupt changes, edges), enhancement of properties of a given object by juxtaposed information which either changes the percept of those properties, or else provides a context that changes the percept of what the object is, and influences of familiarity and probability which can be profound enough to fly in the face of contrary sensory evidence. These data are used to support the hypothesis that perceived linguistic units, including distinctive features, are ephemeral (and illusory) ‘auditory objects’, which are created by the listening brain using domain-general processes that underpin meaningful behaviour.