Sound-induced Flash Illusion Research Articles

Implicit semantics gates visual awareness

The current study asked whether impoverished peripheral vision led to perception immune from word-based semantic influences. We leveraged a peripheral sound-induced flash illusion. In each trial, two or three Mandarin characters were flashed quickly in the periphery with number-congruent or -incongruent beeps. We first successfully replicated the original illusions, showing auditory dominance. For example, when three characters were presented together with two beeps, the observer reported perceiving only two characters. Similarly, an additional beep induced an illusory visual percept. Crucially, when the three characters formed a meaningful word, the lack of a concurrent beep suppressed the awareness to a greater extent. A separate experiment replicated the effect on participants who were unable to recognize the words. When the reading was disrupted by reversing the presentation order, the effect disappeared. These findings demonstrate the capacity of our visual system to extract peripheral linguistic information without conscious word recognition.

Audiovisual integration and sensory dominance effects in older adults with subjective cognitive decline: Enhanced redundant effects and stronger fusion illusion susceptibility.

Subjective cognitive decline (SCD) refers to individuals' perceived decline in memory and/or other cognitive abilities relative to their previous level of performance. Sensory decline is one of the main manifestations of decline in older adults with SCD. The efficient integration of visual and auditory information, known as audiovisual integration, is a crucial perceptual process. This study aims to evaluate audiovisual integration in older adults with SCD. We adopted the audiovisual detection task, the Colavita task, and the Sound-Induced Flash Illusion (SIFI) task to evaluate the audiovisual integration by examining both redundant and illusory effects. Older adults diagnosed with SCD (N=50, mean age=67.8 years) and a control group of non-SCD older adults (N=51, mean age=66.5 years) were recruited. All participants took part in the three aforementioned experiments. The outcomes showed that a redundant effect occurred in both SCD and non-SCD older adults, with SCD older adults gaining more benefits in audiovisual detection task. Moreover, an equivalent amount of the visual dominance effect was observed among both SCD and non-SCD older adults in Colavita task. In addition, older adults with SCD perceived an equal fission illusion but a bigger fusion illusion compared with non-SCD older adults in SIFI task. Overall, older adults with SCD exhibit increased audiovisual redundant effects and stronger fusion illusion susceptibility compared to non-SCD older adults. Besides, visual dominance was observed in both groups via the Colavita task, with no significant difference between non-SCD and SCD older adults. These findings implied that audiovisual integration might offer a potential way for the identification of SCD.

Is a sex difference in audio-visual temporal precision consistent across age groups? An update on Hernández et al. (2019).

Hernández et al. (2019) previously reported independent age and sex differences in temporal audio-visual integration in a large national cohort of older adults. Susceptibility to the sound induced flash illusion (SIFI) at long stimulus onset asynchronies (SOAs) increased with age and was stronger in older adult females than males. However, it is unclear if this sex difference is stable across age. We reanalyzed the data set used by Hernández et al. (2019) on SIFI performance from 3,479 older adults (Mage = 64.20 years, SD = 7.77, range = 50-93; 56% female) across three age groups (50-64, 65-74, and 75+ years), drawn from The Irish Longitudinal Study on Ageing. For the 70 ms SOA, females were less susceptible to the SIFI than males, irrespective of age. At longer SOAs (150 ms and 230 ms), females aged 50-64 years but not older were more susceptible to the SIFI than age-matched males. These findings extend those of Hernández et al. (2019) by indicating that age and sex can collectively influence the precision of multisensory integration exhibited by older adults. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Nutrition is associated with differences in multisensory integration in healthy older adults

ABSTRACT Diet can influence cognitive functioning in older adults and is a modifiable risk factor for cognitive decline. However, it is unknown if an association exists between diet and lower-level processes in the brain underpinning cognition, such as multisensory integration. We investigated whether temporal multisensory integration is associated with daily intake of fruit and vegetables (FV) or products high in fat/sugar/salt (FSS) in a large sample (N = 2,693) of older adults (mean age = 64.06 years, SD = 7.60; 56% female) from The Irish Longitudinal Study on Ageing (TILDA). Older adults completed a Food Frequency Questionnaire from which the total number of daily servings of FV and FSS items respectively was calculated. Older adults’ susceptibility to the Sound Induced Flash Illusion (SIFI) measured the temporal precision of audio-visual integration, which included three audio-visual Stimulus Onset Asynchronies (SOAs): 70, 150 and 230 ms. Older adults who self-reported a higher daily consumption of FV were less susceptible to the SIFI at the longest versus shortest SOAs (i.e. increased temporal precision) compared to those reporting the lowest daily consumption (p = .013). In contrast, older adults reporting a higher daily consumption of FSS items were more susceptible to the SIFI at the longer versus shortest SOAs (i.e. reduced temporal precision) compared to those reporting the lowest daily consumption (p < .001). The temporal precision of multisensory integration is differentially associated with levels of daily consumption of FV versus products high in FSS, consistent with broader evidence that habitual diet is associated with brain health.

Perceptual Training as Means to Assess the Effect of Alpha Frequency on Temporal Binding Window.

For decades, it has been shown that alpha frequency is related to temporal binding window, and currently, such is the mainstream viewpoint [Noguchi, Y. Individual differences in beta frequency correlate with the audio-visual fusion illusion. Psychophysiology, 59, e14041, 2022; Gray, M. J., & Emmanouil, T. A. Individual alpha frequency increases during a task but is unchanged by alpha-band flicker. Psychophysiology, 57, e13480, 2020; Hirst, R. J., McGovern, D. P., Setti, A., Shams, L., & Newell, F. N. What you see is what you hear: Twenty years of research using the sound-induced flash illusion. Neuroscience & Biobehavioral Reviews, 118, 759-774, 2020; Keil, J. Double flash illusions: Current findings and future directions. Frontiers in Neuroscience, 14, 298, 2020; Migliorati, D., Zappasodi, F., Perrucci, M. G., Donno, B., Northoff, G., Romei, V., & Costantini, M. Individual alpha frequency predicts perceived visuotactile simultaneity. Journal of Cognitive Neuroscience, 32, 1-11, 2020; Keil, J., & Senkowski, D. Individual alpha frequency relates to the sound-induced flash illusion. Multisensory Research, 30, 565-578, 2017; Minami, S., & Amano, K. Illusory jitter perceived at the frequency of alpha oscillations. Current Biology, 27, 2344-2351, 2017; Cecere, R., Rees, G., & Romei, V. Individual differences in alpha frequency drive crossmodal illusory perception. Current Biology, 25, 231-235, 2015]. However, recently, this stance has been challenged [Buergers, S., & Noppeney, U. The role of alpha oscillations in temporal binding within and across the senses. Nature Human Behaviour, 6, 732-742, 2022]. Moreover, both stances appear to have their limitations regarding the reliability of results. Therefore, it is of paramount importance to develop new methodology to gain more reliable results. Perceptual training seems to be such a method that also offers significant practical implications.

Virtual reality as a tool to explore multisensory processing before and after engagement in physical activity.

This pilot study employed a non-randomized control trial design to explore the impact of physical activity within a virtual reality (VR) environment on multisensory processing among community-dwelling older adults. The investigation compared both chronic (over 6 weeks) and acute effects of VR-based physical activity to a reading control group. The evaluation metrics for multisensory processing included audiovisual response time (RT), simultaneity judgments (SJ), sound-induced flash illusion (SIFI), and temporal order judgments (TOJ). A total of 13 older adults were provided with VR headsets featuring custom-designed games, while another 14 older adults were assigned to a reading-based control group. Results indicated that acute engagement in physical activity led to higher accuracy in the SIFI task (experimental group: 85.6%; control group: 78.2%; p = 0.037). Additionally, both chronic and acute physical activity resulted in quicker response times (chronic: experimental group = 336.92; control group = 381.31; p = 0.012; acute: experimental group = 333.38; control group = 383.09; p = 0.006). Although the reading group showed a non-significant trend for greater improvement in mean RT, covariate analyses revealed that this discrepancy was due to the older age of the reading group. The findings suggest that immersive VR has potential utility for enhancing multisensory processing in older adults. However, future studies must rigorously control for participant variables like age and sex to ensure more accurate comparisons between experimental and control conditions.

Ability to Process Multisensory Information Is Impaired in Open Angle Glaucoma.

Patients with glaucoma demonstrated deficiencies in their ability to process multisensory information when compared with controls, with those deficiencies being related to glaucoma severity. Impaired multisensory integration (MSI) may affect the quality of life in individuals with glaucoma and may contribute to the increased prevalence of falls and driving safety concerns. Therapeutic possibilities to influence cognition in glaucoma should be explored. Glaucoma is a neurodegenerative disease of the optic nerve that has also been linked to cognitive health decline. This study explored MSI as a function of glaucoma status and severity. MSI was assessed in 37 participants with open angle glaucoma relative to 18 age-matched healthy controls. The sound-induced flash illusion was used to assess MSI efficiency. Participants were presented with various combinations of simultaneous visual and/or auditory stimuli and were required to indicate the number of visual stimuli observed for each of the 96 total presentations. Central retinal sensitivity was assessed as an indicator of glaucoma severity (MAIA; CenterVue). Participants with glaucoma performed with equivalent capacity to healthy controls on unisensory trials ( F1,53 =2.222, P =0.142). Both groups performed equivalently on congruent multisensory trials involving equal numbers of auditory and visual stimuli F1,53 =1.032, P =0.314). For incongruent presentations, that is, 2 beeps and 1 flash stimulus, individuals with glaucoma demonstrated a greater influence of the incongruent beeps when judging the number of flashes, indicating less efficient MSI relative to age-matched controls ( F1,53 =11.45, P <0.002). In addition, MSI performance was positively correlated with retinal sensitivity ( F3,49 =4.042, P <0.025), adjusted R ²=0.15). Individuals with open angle glaucoma exhibited MSI deficiencies that relate to disease severity. The type of deficiencies observed were similar to those observed among older individuals with cognitive impairment and balance issues. Impaired MSI may, therefore, be relevant to the increased prevalence of falls observed among individuals with glaucoma, a concept that merits further investigation.

Audio-visual integration is more precise in older adults with a high level of long-term physical activity.

It is well established that physical activity leads to numerous health, cognitive, and psychological benefits. However, to date, very few studies have investigated the impact of physical activity on multisensory perception, that is, the brain's capacity to integrate information across sensory modalities. Furthermore, it is unknown what level of long-term physical activity is associated with multisensory integration in adults. We explored the relationship between multisensory integration and a ten-year physical activity trajectory in 2,974 adults aged 50+ from The Irish Longitudinal Study on Ageing by measuring susceptibility to the Sound Induced Flash Illusion (SIFI) at multiple audio-visual temporal asynchronies. Physical activity was measured using the International Physical Activity Questionnaire (IPAQ-SF) at 2 years intervals over ten years. We used latent class trajectory modelling to identify latent growth classes of individuals following a similar trajectory of physical activity over time. We analysed the association of this trajectory with performance accuracy to the illusion trials of the SIFI task with generalized logistic mixed effects regression models, adjusted for several covariates. Results showed that more precise integration (i.e., lower SIFI susceptibility with larger temporal asynchronies) was associated with a higher level of sustained physical activity across ten years. Although the use of self-reported physical activity and a short version of the SIFI task limit our conclusions to some extent, nonetheless, the results suggest that sustained physical activity is associated with more precise multisensory integration, which in turn is linked to better balance and a lower risk of falling in older adults.

Subjective Audibility Modulates the Susceptibility to Sound-Induced Flash Illusion: Effect of Loudness and Auditory Masking.

When a brief flash is presented along with two brief sounds, the single flash is often perceived as two flashes. This phenomenon is called a sound-induced flash illusion, in which the auditory sense, with its relatively higher reliability in providing temporal information, modifies the visual perception. Decline of audibility due to hearing impairment is known to make subjects less susceptible to the flash illusion. However, the effect of decline of audibility on susceptibility to the illusion has not been directly investigated in subjects with normal hearing. The present study investigates the relationship between audibility and susceptibility to the illusion by varying the sound pressure level of the stimulus. In the task for reporting the number of auditory stimuli, lowering the sound pressure level caused the rate of perceiving two sounds to decrease on account of forward masking. The occurrence of the illusory flash was reduced as the intensity of the second auditory stimulus decreased, and was significantly correlated with the rate of perceiving the two auditory stimuli. These results suggest that the susceptibility to sound-induced flash illusion depends on the subjective audibility of each sound.

Individual differences in seated resting heart rate are associated with multisensory perceptual function in older adults.

There is evidence that cardiovascular function can influence sensory processing and cognition, which are known to change with age. However, whether the precision of unisensory and multisensory temporal perception is influenced by cardiovascular activity in older adults is uncertain. We examined whether seated resting heart rate (RHR) was associated with unimodal visual and auditory temporal discrimination as well as susceptibility to the audio-visual Sound Induced Flash Illusion (SIFI) in a large sample of older adults (N = 3232; mean age = 64.17 years, SD = 7.74, range = 50-93; 56% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). Faster seated RHR was associated with better discretization of two flashes (but not two beeps) and increased SIFI susceptibility when the audio-visual stimuli were presented close together in time but not at longer audio-visual temporal offsets. Our findings suggest a significant relationship between cardiovascular activity and the precision of visual and audio-visual temporal perception in older adults, thereby providing novel evidence for a link between cardiovascular function and perceptual function in aging.

Metacognitive awareness in the sound-induced flash illusion.

Hundreds (if not thousands) of multisensory studies provide evidence that the human brain can integrate temporally and spatially discrepant stimuli from distinct modalities into a singular event. This process of multisensory integration is usually portrayed in the scientific literature as contributing to our integrated, coherent perceptual reality. However, missing from this account is an answer to a simple question: how do confidence judgements compare between multisensory information that is integrated across multiple sources, and multisensory information that comes from a single, congruent source in the environment? In this paper, we use the sound-induced flash illusion to investigate if confidence judgements are similar across multisensory conditions when the numbers of auditory and visual events are the same, and the numbers of auditory and visual events are different. Results showed that congruent audiovisual stimuli produced higher confidence than incongruent audiovisual stimuli, even when the perceptual report was matched across the two conditions. Integrating these behavioural findings with recent neuroimaging and theoretical work, we discuss the role that prefrontal cortex may play in metacognition, multisensory causal inference and sensory source monitoring in general. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Evidence for an association between allostatic load and multisensory integration in middle-aged and older adults

Multisensory integration, the ability of the brain to integrate information from different sensory modalities, is critical for responding to environmental stimuli. While older adults show changes in multisensory integration with age, the impact of allostatic load (AL) (i.e., the effect of exposure to chronic stress, which can accelerate ageing) on multisensory perception remains understudied. We explored the relationship between multisensory integration and AL in 1,358 adults aged 50+ from The Irish Longitudinal Study on Ageing by performing a Sound Induced Flash Illusion (SIFI) task at multiple audio-visual temporal asynchronies. The AL score was created using a battery of biomarkers representing the activity of four major physiological systems: immunological, cardiovascular, metabolic, and renal. The number of biomarkers for which a participant was categorised in the highest risk quartile using sex-specific cutoffs was used to produce an overall AL score. We accounted for medication use when calculating our AL score. We analysed the accuracy of illusion trials on a SIFI task using generalised logistic mixed effects regression models adjusted for a number of covariates. Observation of cross-sectional and longitudinal results revealed that lower accuracy in integration (i.e., higher SIFI susceptibility with larger temporal asynchronies) was associated with higher AL. This confirmed the distinct patterns of multisensory integration in ageing.

Rhythmic TMS as a Feasible Tool to Uncover the Oscillatory Signatures of Audiovisual Integration.

Multisensory integration is quintessential to adaptive behavior, with clinical populations showing significant impairments in this domain, most notably hallucinatory reports. Interestingly, altered cross-modal interactions have also been reported in healthy individuals when engaged in tasks such as the Sound-Induced Flash-Illusion (SIFI). The temporal dynamics of the SIFI have been recently tied to the speed of occipital alpha rhythms (IAF), with faster oscillations entailing reduced temporal windows within which the illusion is experienced. In this regard, entrainment-based protocols have not yet implemented rhythmic transcranial magnetic stimulation (rhTMS) to causally test for this relationship. It thus remains to be evaluated whether rhTMS-induced acoustic and somatosensory sensations may not specifically interfere with the illusion. Here, we addressed this issue by asking 27 volunteers to perform a SIFI paradigm under different Sham and active rhTMS protocols, delivered over the occipital pole at the IAF. Although TMS has been proven to act upon brain tissues excitability, results show that the SIFI occurred for both Sham and active rhTMS, with the illusory rate not being significantly different between baseline and stimulation conditions. This aligns with the discrete sampling hypothesis, for which alpha amplitude modulation, known to reflect changes in cortical excitability, should not account for changes in the illusory rate. Moreover, these findings highlight the viability of rhTMS-based interventions as a means to probe the neuroelectric signatures of illusory and hallucinatory audiovisual experiences, in healthy and neuropsychiatric populations.

Older adults with slow sit to stand times show reduced temporal precision of audio–visual integration

Sustained integration of sensory inputs over increased temporal delays is associated with reduced cognitive and physical functioning in older adults and adverse outcomes such as falls. Here, we explored the relationship between multisensory integration and a clinically relevant measure of balance/postural control; Sit-to-Stand Time, the efficiency with which an older adult can transition between a seated and a standing posture. We investigated whether temporal multisensory integration was associated with performance on the Five-Times Sit-to-Stand Test (FTSST) in a large sample of 2556 older adults (mean age = 63.62 years, SD = 7.50; 55% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). K-means clustering was applied to FTSST data, yielding three clusters characterised by fast (mean = 10.88 s; n = 1122), medium (mean = 14.34 s; n = 1133) and slow (mean = 18.97 s; n = 301) sit-to-stand times. At wave 3 of TILDA, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio–visual integration, which included three audio–visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Older adults with the slowest sit-to-stand times were more susceptible to the SIFI at the longest SOA (230 ms) compared to the shortest SOA (70 ms) relative to those with the fastest times (p = 0.02). Older adults who take longer to repeatedly transition from a seated to a standing posture exhibit an expanded temporal binding window for audio–visual events, supporting a link between multisensory perception and balance/postural control in ageing.

The temporal precision of audiovisual integration is associated with longitudinal fall incidents but not sensorimotor fall risk in older adults

Sustained multisensory integration over long inter-stimulus time delays is typically found in older adults, particularly those with a history of falls. However, the extent to which the temporal precision of audio-visual integration is associated with longitudinal fall or fall risk trajectories is unknown. A large sample of older adults (N = 2319) were grouped into longitudinal trajectories of self-reported fall incidents (i.e., decrease, stable, or increase in number) and, separately, their performance on a standard, objective measure of fall risk, Timed Up and Go (TUG; stable, moderate decline, severe decline). Multisensory integration was measured once as susceptibility to the Sound-Induced Flash Illusion (SIFI) across three stimulus onset asynchronies (SOAs): 70 ms, 150 ms and 230 ms. Older adults with an increasing fall number showed a significantly different pattern of performance on the SIFI than non-fallers, depending on age: For adults with increasing incidents of falls, those aged 53–59 years showed a much smaller difference in illusion susceptibility at 70 ms versus 150 ms than those aged 70 + years. In contrast, non-fallers showed a more comparable difference between these SOA conditions across age groups. There was no association between TUG performance trajectories and SIFI susceptibility. These findings suggests that a fall event is associated with distinct temporal patterns of multisensory integration in ageing and have implications for our understanding of the mechanisms underpinning brain health in older age.

Visual adaptation changes the susceptibility to the fission illusion.

Sound-induced flash illusion (SiFI) is the illusion that participants perceive incorrectly that the number of visual flashes is equal to the number of auditory beeps when presented within 100 ms. Although previous studies found that repetition suppression can reduce an individual's perceptual sensitivity to the SiFI, there is not yet a consensus as to how visual adaptation affects the SiFI. In the present study, we added prolonged adapting visual stimuli prior to the presentation of audiovisual stimuli to investigate whether the bottom-up factor of adaptation affects the SiFI. The adapting visual stimuli consisted of one or two of the same visual stimuli that lasted for 2 minutes in succession, followed by the audiovisual stimuli. Both adaptation conditions showed SiFI effects. The accuracy of adapting double-flashes was significantly lower than that of in adapting a single flash for the fission illusion. Our analyses indicated that such a pattern could be attributed to a lower d' in adapting double-flashes than in adapting a single flash. However, the accuracy, discriminability and criterion were not significantly different between the two adaptation conditions because of the instability of the fusion illusion. Thus, the present study indicated that the reduced perceptual sensitivity based on visual adaptation could enhance the fission illusion in multisensory integration.

The effects of estradiol levels on crossmodal perception: a study on the sound induced flash illusion in healthy and menstrually related migraine individuals

ObjectiveThe sound-induced flash illusion (SIFI) is a valid paradigm to study multisensorial perception. In the “fission” SIFI, multiple flashes are perceived when observing a single flash paired with two or more beeps. SIFI is largely dependent on visual and acoustic cortex excitability; in migraine, dysfunctional cortical excitability affects SIFI perception. Since estrogen peak occurring during ovulation can increase neuronal excitability, the present study aims to verify whether cortical excitability shifts linked to the menstrual cycle could influence SIFI.MethodsIn a comparative prospective study, we tested the effect of estrogens on crossmodal perception using the SIFI. We recruited 27 females in reproductive age, including 16 healthy and 11 menstrually related migraine females, testing their proneness to SIFI on day 14 (high estradiol) and day 27 (low estradiol) of menstrual cycle.ResultsWomen on day 14 reported less flashes than on day 27 (p = 0.02) in the fission illusion, suggesting a pro-excitatory effect of estradiol on visual cortex excitability during ovulation. Moreover, we confirmed that migraine women perceived less flashes (p = 0.001) than controls, independently from cycle phase. Non-migraineurs women significantly reported more flashes on day 27 than on day 14 (p = 0.04).ConclusionsThis study suggests that estradiol may influence the multisensory perception due to changes of visual cortex excitability, with high estradiol peak leading to increased visual cortical sensitivity during ovulation in non-migraineurs. Visual cortex hyperresponsiveness, here reflected by reduced SIFI, is not influenced by estradiol fluctuations in migraine women, as shown by reduced fission effects on day 14 and 27.

Susceptibility to the sound-induced flash illusion is associated with gait speed in a large sample of middle-aged and older adults

BackgroundMultisensory integration is the ability to appropriately merge information from different senses for the purpose of perceiving and acting in the environment. During walking, information from multiple senses must be integrated appropriately to coordinate effective movements. We tested the association between a well characterised multisensory task, the Sound-Induced Flash Illusion (SIFI), and gait speed in 3255 participants from The Irish Longitudinal Study on Ageing. High susceptibility to this illusion at longer stimulus onset asynchronies characterises older adults, and has been associated with cognitive and functional impairments, therefore it should be associated with slower gait speed. MethodGait was measured under three conditions; usual pace, cognitive dual tasking, and maximal walking speed. A separate logistic mixed effects regression model was run for 1) gait at usual pace, 2) change in gait speed for the cognitive dual tasking relative to usual pace and 3) change in maximal walking speed relative to usual pace. In all cases a binary response indicating a correct/incorrect response to each SIFI trial was the dependent variable. The model controlled for covariates including age, sex, education, vision and hearing abilities, Body Mass Index, and cognitive function. ResultsSlower gait was associated with more illusions, particularly at longer temporal intervals between the flash-beep pair and the second beep, indicating that those who integrated incongruent sensory inputs over longer intervals, also walked slower. The relative changes in gait speed for cognitive dual tasking and maximal walking speed were also significantly associated with SIFI at longer SOAs. ConclusionsThese findings support growing evidence that mobility, susceptibility to falling and balance control are associated with multisensory processing in ageing.

Audiovisual illusion training improves multisensory temporal integration

When we perceive external physical stimuli from the environment, the brain must remain somewhat flexible to unaligned stimuli within a specific range, as multisensory signals are subject to different transmission and processing delays. Recent studies have shown that the width of the ‘temporal binding window (TBW)’ can be reduced by perceptual learning. However, to date, the vast majority of studies examining the mechanisms of perceptual learning have focused on experience-dependent effects, failing to reach a consensus on its relationship with the underlying perception influenced by audiovisual illusion. The sound-induced flash illusion (SiFI) training is a reliable function for improving perceptual sensitivity. The present study utilized the classic auditory-dominated SiFI paradigm with feedback training to investigate the effect of a 5-day SiFI training on multisensory temporal integration, as evaluated by a simultaneity judgment (SJ) task and temporal order judgment (TOJ) task. We demonstrate that audiovisual illusion training enhances multisensory temporal integration precision in the form of (i) the point of subjective simultaneity (PSS) shifts to reality (0 ms) and (ii) a narrowing TBW. The results are consistent with a Bayesian model of causal inference, suggesting that perception learning reduce the susceptibility to SiFI, whilst improving the precision of audiovisual temporal estimation.

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.