Temporal integration of consecutive tones into synthetic vowels demonstrates perceptual assembly in audition

Temporal integration is the perceptual process combining sensory stimulation over time into longer percepts that can span over 10 times the duration of a minimally detectable stimulus. Particularly in the auditory domain, such "long-term" temporal integration has been characterized as a relatively simple function that acts chiefly to bridge brief input gaps, and which places integrated stimuli on temporal coordinates while preserving their temporal order information. These properties are not observed in visual temporal integration, suggesting they might be modality specific. The present study challenges that view. Participants were presented with rapid series of successive tone stimuli, in which two separate, deviant target tones were to be identified. Critically, the target tone pair would be perceived as a single synthetic vowel if they were interpreted to be simultaneous. During the task, despite that the targets were always sequential and never actually overlapping, listeners frequently reported hearing just one sound, the synthetic vowel, rather than two successive tones. The results demonstrate that auditory temporal integration, like its visual counterpart, truly assembles a percept from sensory inputs across time, and does not just summate time-ordered (identical) inputs or fill gaps therein. This finding supports the idea that temporal integration is a universal function of the human perceptual system.