Perception of visual apparent motion is modulated by a gap within concurrent auditory glides, even when it is illusory

Long-term Tai Chi training reduces the fusion illusion in older adults

Sound-induced flash illusion (SiFI) is an auditory-dominated audiovisual integration phenomenon that can be used as a reliable indicator of audiovisual integration. Although previous studies have found that Tai Chi exercise has a promoting effect on cognitive processing, such as executive functions, the effect of Tai Chi exercise on early perceptual processing has yet to be investigated. This study used the classic SiFI paradigm to investigate the effects of long-term Tai Chi exercise on multisensory integration in older adults. We compared older adults with long-term Tai Chi exercise experience with those with long-term walking exercise. The results showed that the accuracy of the Tai Chi group was higher than that of the control group under the fusion illusion condition, mainly due to the increased perceptual sensitivity to flashes. However, there was no significant difference between the two groups in the fission illusion. These results indicated that the fission and fusion illusions were affected differently by Tai Chi exercise, and this was attributable to the association of the participants' flash discriminability with them. The present study provides preliminary evidence that long-term Tai Chi exercise improves older adults' multisensory integration, which occurs in early perceptual processing.

Roles of temporal proximity between sound edges in the perceptual organization of veridical and illusory auditory events

The gap transfer illusion is an auditory illusion in which a temporal gap in a long glide is perceived as if it had transferred to a physically continuous shorter glide. The illusion typically occurs when the long and the shorter glide cross each other at their temporal midpoints, where the long glide is physically divided by the gap. The occurrence of the gap transfer illusion was investigated in stimuli in which the duration and the slope of the long glide were 5000 ms and ∼0.8 oct/s. The shorter glide was given different frequency ranges and different temporal ranges, and thus its time-frequency slope was also varied. The overlap configuration of these crossing glides was varied as well. As control stimuli, we used stimuli in which a continuous long glide crossed a shorter glide with a gap, i.e., the opposite configuration of the gap-transfer stimuli as above, as well as stimuli in which both crossing glides were continuous. The perception of two crossing tones tended to be facilitated when the glides differed in duration and/or slope. When the glides were relatively similar in duration and slope, however, bouncing percepts appeared more often. Similarity between the crossing tones thus promoted auditory bouncing, while dissimilarity between them facilitated the crossing percept. If the crossing percept dominated in gap-transfer stimuli, the gap transfer illusion took place in a typical manner, but the illusory transfer of the gap could occur even when the crossing percept was not dominant. When the shorter glide was as short as 500 ms, the crossing percept and the gap transfer illusion were robust. The mechanism of the illusion was examined in terms of factors that can influence the perceptual integration of auditory stimulus edges, i.e., onsets and offsets, of physically different sounds. Much like the perceptual construction of speech units, we suggest that the auditory system utilizes a rough time window of several hundreds of milliseconds to construct an initial skeleton percept of auditory events. The present data indicated the importance of the temporal proximity, rather than the frequency proximity, between sound edges in the illusory tone construction.

Cognitive Styles Differentiate Crossmodal Correspondences Between Pitch Glide and Visual Apparent Motion

Crossmodal correspondences are the automatic associations that most people have between different basic sensory stimulus attributes, dimensions, or features. For instance, people often show a systematic tendency to associate moving objects with changing pitches. Cognitive styles are defined as an individual's consistent approach to think, perceive, and remember information, and they reflect qualitative rather than quantitative differences between individuals in their thinking processes. Here we asked whether cognitive styles played a role in modulating the crossmodal interaction. We used the visual Ternus display in our study, since it elicits two distinct apparent motion percepts: element motion (with a shorter interval between the two Ternus frames) and group motion (with a longer interval between the two frames). We examined the audiovisual correspondences between the visual Ternus movement directions (upward or downward) and the changes of pitches of concurrent glides (ascending frequency or descending frequency). Moreover, we measured the cognitive styles (with the Embedded Figure Test) for each participant. The results showed that congruent correspondence between pitch-ascending (decreasing) glides and moving upward (downward) visual directions led to a more dominant percept of 'element motion', and such an effect was typically observed in the field-independent group. Importantly, field-independent participants demonstrated a high efficiency for identifying the properties of audiovisual events and applying the crossmodal correspondence in crossmodal interaction. The results suggest cognitive styles could differentiate crossmodal correspondences in crossmodal interaction.