COMMONALITIES AND DIFFERENCES IN VISUAL AND AUDITORY MULTISTABILITY
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Perceptual bi/multi-stability—the phenomenon in which perceptual awareness switches between alternative interpretations of a stimulus—can be elicited by a large range of stimuli. The phenomenon is explored in vision, audition, touch, and even olfaction. The degree to which perceptual switching across visual and auditory bi/multi-stable paradigms depends on common or separate mechanisms remains unanswered. This main question was addressed in the current work by using four ambiguous tasks that give rise to bi/multi-stability and which are thought to involve rivalry at different levels of cognitive processing: auditory streaming and ambiguous-structure-from-motion (low- level tasks), and verbal transformations and ambiguous figures (high-level tasks). It was also investigated if individual differences in executive function (inhibitory control and set-shifting), creativity and personality traits have common relationships with perceptual switching in adults and children. A series of five experiments (four studies) were conducted. In Study 1 (two experiments), perceptual switching behaviour of adult participants was examined in the four perceptual tasks mentioned above. In Experiment 1, participants reported higher switching rates for the ambiguous figure and verbal transformations than for ambiguous motion and auditory streaming. However, in Experiment 2 participants had a higher switching rate in verbal transformations than in auditory streaming, while the switching rates in the two visual tasks did not differ significantly. The correlations between visual and auditory switching rates were similarly inconclusive: in Experiment 1, no cross-modal correlations emerged, while in Experiment 2 there were correlations between ambiguous figure and verbal transformations and between ambiguous motion and verbal transformation. Furthermore, inhibitory control, set-shifting, and creativity correlated with perceptual ii switching rates in some of the perceptual tasks, although not in a consistent manner. In Study 2, the development of perceptual switching was investigated in children in the same four tasks used in Study 1. Findings showed that the number of switches increased with age in all four perceptual tasks, indicating general maturational developments. Executive functions and creativity were not associated with the ongoing perceptual switching, which was similar to what was found in adults. In Study 3, a neuroscientific perturbation approach was used to investigate whether the superior parietal cortex is causally involved in both visual and auditory multistability as a top-down mechanism. Transcranial magnetic stimulation on the anterior and posterior superior parietal cortex did not increase or decrease the median phase durations in response to the ambiguous motion and auditory streaming. These regions were not causally involved in either visual or auditory multistability. Perceptual switching across modalities correlated nevertheless, indicating common perceptual mechanisms. In Study 4, the effects of attentional control and instructions were further investigated in ambiguous motion and auditory streaming. There were strong correlations between perceptual switching in the two tasks, confirming that there are common mechanisms. However, the effects of voluntary attention did not explain the commonalities found. Possibly the commonalities found reflect similar functionalities at more low-level sensorial mechanisms. In conclusion, perceptual switching in vision and audition share common mechanisms. These commonalities do not seem to be due to the same neural underpinning in parietal cortex. Moreover, attentional control does not explain the commonalities found, indicating a more low-level common mechanism or functionality. Perceptual switching across all ages is task-specific, more than modality specific. No central influence of inhibitory control and creativity was constantly associated with perceptual switching regardless of task/modality, supporting the distributed mechanisms hypothesis.
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