Perceptuo-motor interactions in the perceptual organization of speech: evidence from the verbal transformation effect

Abstract

The verbal transformation effect (VTE) refers to perceptual switches while listening to a speech sound repeated rapidly and continuously. It is a specific case of perceptual multistability providing a rich paradigm for studying the processes underlying the perceptual organization of speech. While the VTE has been mainly considered as a purely auditory effect, this paper presents a review of recent behavioural and neuroimaging studies investigating the role of perceptuo-motor interactions in the effect. Behavioural data show that articulatory constraints and visual information from the speaker's articulatory gestures can influence verbal transformations. In line with these data, functional magnetic resonance imaging and intracranial electroencephalography studies demonstrate that articulatory-based representations play a key role in the emergence and the stabilization of speech percepts during a verbal transformation task. Overall, these results suggest that perceptuo (multisensory)-motor processes are involved in the perceptual organization of speech and the formation of speech perceptual objects.

High-frequency neural activity predicts word parsing in ambiguous speech streams

“…The sequences and the reporting instructions were identical to the volitional task: participants depressed a button corresponding to their current percept (3 possibilities: "percept 1," "percept 2," or "other"). As in prior findings, participants did not report hearing the two percepts in equal proportions, but rather mostly reported hearing the initial veridical word repeated in the sequence (Basirat et al 2012;Sato et al 2007). Nevertheless, and with many cautionary steps, we performed a comparable analysis as for the volitional data.…”

“…Four auditory sequences (adapted from Basirat et al 2012 andSato et al 2007) were presented binaurally to participants via Etymotic earphones (Etymotic Research, Elk Grove Village, IL) at a comfortable hearing level. One sequence consisted of the repetition of the monosyllabic French word "lampe" ([lãp], French equivalent of "lamp").…”

“…First, before beginning the main experiment, participants were familiarized with the stimuli via the spontaneous verbal transformation task (Basirat et al 2012), in which participants hear a sequence of repeated acoustic utterances yielding bistable auditory percepts. Participants were asked to spontaneously report their perception while listening to these auditory sequences.…”

“…These results confirmed that with this task, the perception of the repeated word in the sequence could be manipulated while keeping the acoustic signal constant. Volitional control also limited the biases observed during spontaneous bistable perception in which participants typically report hearing mainly one word repeated in the sequence and not the two bistable percepts in balance (see Basirat et al 2012;Sato et al 2007). …”

“…In this experiment, we were interested in understanding whether neural oscillatory dynamics predicted linguistic parsing when the acoustic properties of speech were maintained identically over time yet yielded different conscious percepts, a phenomenon known as "verbal transformations" (Basirat et al 2012;Billig et al 2013;Sato et al 2006Sato et al , 2007Warren 1968) (Fig. 1A).…”