Flash illusions induced by visual, auditory, and audiovisual stimuli

Abstract

When two objects are flashed at one location in close temporal proximity in the visual periphery, an intriguing illusion occurs whereby a single flash presented concurrently at another location appears to flash twice (the visual double-flash illusion: Chatterjee et al., 2011, Wilson & Singer, 1981). Here, for the first time, we investigate the time course of the effect, and directly compare it to the time course of the auditory (sound-induced flash illusion) effect, for both fission (single test flash, double inducer) and fusion (double test flash, single inducer) conditions, across stimulus onset asynchronies (SOAs) of 30 to 250 ms. In addition, using a novel audiovisual stimulus, we directly compare the cue strength of the two modalities, and whether they are additive in effect. The results show that the time course of fission and fusion is different for visual inducers, but not for auditory inducers. In audiovisual conditions, in situations of uncertainty, observers tended to follow the more reliable (auditory) cue. There was little evidence for a superadditive effect of auditory and visual cues; rather, observers tended to follow one or the other modality. The results suggest that the visually induced flash illusion and the auditory-induced effect may both stem from perceptual uncertainty, with the difference in time courses attributable to the lower temporal resolution of vision compared to audition.

The sound-induced flash illusion reveals dissociable age-related effects in multisensory integration

“…Figure 2 shows the group-averaged proportion of illusory responses to the 1F2B trials for both groups as a function of SOA. Young participants experienced the sound-induced fission illusion when the auditory beep stimuli were separated by short intervals, but their performance improved with increasing SOA, consistent with previous reports (Shams et al, 2002; Setti et al, 2011; Apthorp et al, 2013). In contrast, whereas older adults were as susceptible to the illusion as younger adults at shorter SOAs (33–50 ms), they remained susceptible to the illusion even for the longest SOA presented between the auditory beeps.…”

“…This fusion effect (see Figure 1B) is assessed in an identical manner to the fission illusion and is observed across a similar range of stimulus onset asynchronies in younger participants (Apthorp et al, 2013). As such, it provides an excellent means for assessing whether the age-dependent cost for multisensory integration extends to other conditions that involve the combination of audiovisual signals.…”

“…Although the fission and fusion variants of the sound-induced flash illusion appear similar from a behavioral perspective, there is debate as to whether the two illusions are driven by the same or different neural processes (Mishra et al, 2007, 2008; Apthorp et al, 2013). Apthorp et al suggested that two illusions stemmed from a common mechanism based on the high degree of similarity between the time courses of the fission and fusion illusion in younger participants.…”

The triple-flash illusion reveals a driving role of alpha-band reverberations in visual perception

“…At first glance the triple-flash illusion appears similar to other phantom flash illusions (Wilson and Singer, 1981;Shams et al, 2000;Violentyev et al, 2005;Chatterjee et al, 2011;Apthorp et al, 2013), such as the sound-induced double-flash illusion, whose temporal window has been shown to be causally related to alpha-band oscillations (Cecere et al, 2015). However, there is one critical difference: The illusory third flash in the "triple-flash" illusion is purely endogenous, whereas perception of other phantom flash illusions requires simultaneous presentation of additional stimuli, either in a different modality or in a different spatial location.…”

Audition influences color processing in the sound-induced visual flash illusion

“…According to this hypothesis, audition dominates the temporal component of the multisensory percept because temporal coding is more accurate within audition, whereas vision dominates the qualitative form and spatial properties of the percept. Recent studies have further supported the idea that reliance on the auditory modality for temporal precision is due to its greater predictive certainty in the temporal domain, in accordance with a Bayesian ideal observer (Shams et al, 2005b, Apthorp et al, 2013). Here we show that auditory stimulation not only influences the temporal properties of visual percepts, but also, for very specific audiovisual combinations, audition can affect the degree of perceptual integration versus separation when different colored flashes are presented in rapid succession.…”