Multimodal time perception: The role of temporal ventriloquism in the integration of multisensory intervals of conflicting duration

Abstract

Time perception can be subject to severe perceptual distortions when different sensory modalities provide incongruent temporal information. Specifically, perceived duration of visual intervals is typically impaired by concurrently presented auditory intervals with conflicting durations. However, the literature on multisensory duration perception is so far quite scarce, and thus our knowledge of how multisensory intervals with different durations are processed and integrated is limited. The main aim of the present thesis was therefore to investigate the underlying mechanisms and processes as well as the principles that determine the multisensory integration effects on perceived duration in order to reach a better understanding of multisensory duration integration. Importantly, the major results of the present thesis inform about four relevant aspects of multimodal integration of perceived duration. First, combining audiovisual intervals produced distorted perceived duration within a task-relevant modality when accompanied by task-irrelevant intervals with conflicting durations. Nonetheless, this multimodal conflict did not produce costs on discrimination sensitivity but rather led to more stable duration percepts. Moreover, this integration effect was asymmetric, but bidirectional: auditory task-irrelevant interval duration influenced perceived visual duration more than vice versa. Yet, auditory dominance on the integrated percept is not complete, that is, visual duration information also affected auditory perceived duration to a certain extent. Second, the magnitude of this multimodal integration effect remained constant with increasing interval duration, which can be interpreted in terms of a temporal ventriloquist effect determining the closing/opening of an internal switch mechanism. Third, regarding the locus of the underlying integration process, a simple decisional or strategic bias could be ruled out by demonstrating that perceived visual duration was still affected even when the concurrent auditory stimulation did not provide sufficient information about interval duration. However, there was no evidence that auditory duration directly affects a non-temporal aspect of visual perception, namely, identification of masked letters. Finally, the examination of potential sustained effects showed that multisensory duration integration is produced in only a transient, immediate manner. These latter null results, however, cannot rule out a perceptual account of the multisensory duration integration effects. Further investigation is still needed to provide more direct and compelling evidence on the locus of the processes underlying multisensory integration effects on perceived duration.