The study, led by Tristan Loria with colleagues including Kanji Tanaka, Joëlle Hajj, Katsumi Watanabe, and Luc Tremblay, exploited one of the most famous tricks in perception science: the sound-induced flash illusion. In its classic form, a single flash of light accompanied by two brief beeps is often perceived as two flashes, an error known as the fission illusion. The complementary version, the fusion illusion, occurs when two flashes paired with a single beep collapse perceptually into one. First described by Shams, Kamitani, and Shimojo in 2000, the illusion demonstrates that audition can literally rewrite what we think we see, and it has since become a standard probe for measuring how the brain combines information across the senses.

For decades, the dominant view held that such cross-modal binding occurs automatically whenever stimuli are spatially and temporally congruent, following principles such as near-optimal Bayesian integration, in which the brain weights each sense according to its reliability. But a growing body of evidence has complicated that picture. Attention, cognitive load, expectation, and even clinical conditions such as glaucoma, migraine, and autism spectrum disorder all modulate how strongly the illusion grips the observer. The new study adds a surprising factor to that list: the body’s own goal-directed movements.

The researchers designed two experiments. In the first, participants performed pointing movements toward visual targets while unimodal visual stimuli, congruent audiovisual pairs, or illusion-inducing audiovisual combinations were presented either at the target location itself or at adjacent non-target locations, both close to and far from the target. After completing each movement, participants reported how many flashes they had seen, giving the team a precise measure of perceptual accuracy for each stimulus type at each location. The logic was straightforward: if multisensory perception is uniform across space, accuracy should not depend on where the stimuli appeared relative to the movement goal.

That is not what happened. The results revealed a clear spatial gradient in perceptual accuracy. Bimodal, congruent audiovisual stimuli were processed more accurately at the target location than at either the close or far non-target locations, indicating that the perceptual benefits of combining sight and sound are concentrated where the action is directed. More intriguing still was the pattern for the fusion illusion. Participants were more susceptible to the illusion, meaning lower perceptual accuracy, at the target location, while accuracy was higher at the nearby non-target positions. In other words, the very spot the brain prioritizes for action became the spot where sound most powerfully distorted vision, collapsing two flashes into one.

The second experiment asked whether this modulation depends on actually moving, or whether merely preparing an action is enough. Participants again pointed at targets while the same battery of stimuli was delivered at the target location, but the researchers compared trials in which the movement was executed against a no-movement condition. The answer was unambiguous: the modulation of multisensory perception at the target location appeared only during movement itself, not when participants remained still. This temporal specificity suggests that the efferent signals and sensorimotor processes accompanying active movement, rather than attentional preparation alone, are what reshape the audiovisual percept.

Perhaps the most technically revealing aspect of the study is a double dissociation hiding in the data. Only the fusion illusion, in which two flashes merge into one, was sensitive to both the spatial gradient and the movement manipulation. The fission illusion, in which one flash splits into two under the influence of two beeps, remained remarkably stable across all locations and both action states. This asymmetry aligns with neurophysiological evidence that the two illusions, despite their mirror-image phenomenology, rely on distinct underlying mechanisms. Prior work using electroencephalography has traced fusion to early cross-modal interactions in auditory and visual cortex, while fission appears to engage different, possibly later, processing stages. The new behavioral results suggest that whatever mechanism goal-directed action recruits, it taps into the circuitry underlying fusion but leaves fission untouched.

The findings resonate with a broader literature on action-centered attention and peripersonal space. Research on selective reaching has shown that attention is organized around the body and its intentions rather than around retinal coordinates, and studies of saccade preparation have demonstrated that attention shifts to the goal of an eye movement before it lands. Earlier work by Tremblay and colleagues had already shown decreased sensitivity to an audiovisual illusion during goal-directed reaching, and a 2020 study by Loria, Tanaka, Watanabe, and Tremblay found that deploying attention to a pointing target modulates audiovisual processing even at non-target locations. The new experiments sharpen that picture by separating spatial proximity from movement execution, showing that the two factors interact: space defines where perception is modulated, and action defines when.

Why would the brain deliberately make itself more vulnerable to an illusion at the location it is reaching toward? One plausible interpretation comes from reliability-weighting models of multisensory perception. Peripheral vision is coarse and unreliable, and when visual information is degraded, the brain leans more heavily on the more precise auditory signal, which is exactly the condition under which fusion illusions flourish. During a goal-directed action, resources are funneled toward the target to guide the hand, and the resulting perceptual economy may amplify the relative weight of sound at that location. The paradoxical outcome is that the behaviorally most relevant spot in space becomes the spot where the senses merge most aggressively, a trade-off between sharpening an action plan and accepting perceptual distortion.

The implications extend well beyond the laboratory. Multisensory integration underpins everything from speech perception and virtual reality design to rehabilitation after stroke and the performance of surgeons, pilots, and athletes working in cluttered, noisy environments. If the fidelity of audiovisual binding shifts dynamically with our actions, then interface designers, clinicians, and human-factors engineers may need to account for a moving, action-dependent perceptual landscape rather than a static one. The authors note that the raw data will be made available upon reasonable request, supporting verification and secondary analysis. For now, the message is vivid and a little unsettling: the world you perceive is not a fixed rendering but a construction that your own movements edit in real time, bending sight around sound precisely where you intend to act.

Subject of Research: Modulation of audiovisual multisensory integration and the sound-induced flash illusion by goal-directed action

Article Title: Goal-directed action modulates audiovisual multisensory perception

Article References: Loria, T., Tanaka, K., Hajj, J., Watanabe, K., & Tremblay, L. (2026). Goal-directed action modulates audiovisual multisensory perception. Attention, Perception, & Psychophysics, 88(7), Article 201. https://doi.org/10.3758/s13414-026-03337-1

Image Credits: AI Generated

DOI: 10.3758/s13414-026-03337-1

Keywords: multisensory integration, sound-induced flash illusion, audiovisual perception, goal-directed action, pointing movements, spatial attention, peripersonal space, fusion illusion, fission illusion, sensorimotor processing, psychophysics, attention

The study was inspired by an earlier hypothesis in the field sometimes called sound-induced visual segmentation. When two two-dimensional objects approach one another and reach their point of closest approach, a coincident sound appears to lead observers to overestimate the distance between them, as though the auditory event slices the visual scene into distinct objects. The research team, led by Wenxuan Song, Xiaoying Li, Yuan Guo, and Song Zhao of Soochow University in China, reasoned that if a sound can segment approaching objects in this way, it might also amplify the non-contact illusion that arises when two moving squares disappear precisely at the instant their edges meet. Across two experiments, they tested whether a sound presented at contact would increase the probability that observers report the squares as having never touched.

The results were clear and consistent. In both Experiment 1 and Experiment 2, participants were significantly more likely to give a non-contact response when a sound accompanied the moment of visual contact than when the squares collided in silence. This sound-induced increase in the illusion occurred even though the sound carried no information about the visual stimulus and participants were explicitly instructed to ignore it. The effect is therefore a genuine cross-modal influence: an auditory signal, meaningless on its own, reshapes the conscious perception of a visual event in a systematic and reproducible way.

What makes the finding particularly striking is that the effect runs in the opposite direction from what a simple collision interpretation would predict. The classic stream-bounce literature, dating back to Sekuler and colleagues’ 1997 demonstration that a sound can make two crossing discs appear to bounce off one another, has often been interpreted through the lens of causal inference: the sound suggests a collision, so the brain infers a collision. But in the new study, the sound produced more non-contact judgments, not more contact judgments. If the sound had merely signaled that two objects struck one another, it should have biased observers toward reporting contact. Instead, it deepened the impression that the objects remained apart, ruling out this response-bias account.

The researchers also tested and rejected an attentional explanation. One possibility is that the abrupt sound simply distracts observers, impairing their ability to encode the visual event and thereby pushing them toward a default or guess response. If that were true, non-contact responses in the sound-present condition should have been slower than contact responses, reflecting a disruption of processing. The reaction-time data told a different story: the non-contact response was never slower than the contact response when the sound was present. In fact, supplementary analyses showed that reaction times for non-contact responses were significantly shorter in the sound-present condition than in the sound-absent condition, while contact responses did not differ between sound conditions. This pattern contradicts any account based on attentional distraction or slowed processing.

To probe the neural mechanisms underlying the effect, the team recorded high time-resolution event-related potentials, or ERPs, during Experiment 2. The critical comparison focused on an early cross-modal component known as PD170, a positivity peaking between roughly 125 and 175 milliseconds after sound onset that has previously been associated with low-level audiovisual interactions in early sensory cortex. The results showed that the PD170 was significantly larger on sound-present trials in which participants ultimately reported the non-contact percept than on sound-present trials in which they reported contact. This dissociation, emerging within the first fifth of a second after the sound, indicates that the sound-induced enhancement of the illusion is rooted in early, low-level cross-modal interactions rather than in later cognitive evaluation or decision processes.

The PD170 finding carries substantial theoretical weight. Early cross-modal components of this kind have been linked to interactions between auditory and visual cortex that occur automatically, before attention and higher-order cognition can shape the percept. By tying the strength of the behavioral illusion to the amplitude of this early component, the study substantiates the perceptual nature of the effect: the sound does not merely change what people say about the display but genuinely alters what they see. This aligns the new phenomenon with a family of well-documented sound-induced visual illusions, including the sound-induced flash illusion, in which a single flash accompanied by two beeps is perceived as two flashes, and the audiovisual bounce-inducing effect, in which a sound at the crossing point of two moving discs promotes a bouncing percept.

At the same time, the non-contact illusion and its sound-induced enhancement differ in an important way from the stream-bounce paradigm. The non-contact illusion does not require a sound to emerge; it arises purely from the visual statistics of the display, specifically the sudden disappearance of two squares at the moment their edges make contact. The sound merely strengthens an already-existing visual illusion rather than resolving an ambiguous motion event. This makes the paradigm a particularly clean tool for studying how auditory signals modulate visual spatial perception, because baseline and sound-modulated conditions can be compared within the same unambiguous geometric event. The authors note, following recent work by Zeljko and Grove, that there is no inherent bias toward any particular percept in the sound-absent condition unless it is intermixed with sound-present trials, further underscoring the importance of careful experimental design in this domain.

The methodological rigor of the study strengthens its conclusions. The researchers used mixed-effects logistic modeling with maximal random-effects structures, in line with contemporary best practices for categorical data analysis, and complemented frequentist tests with Bayesian analyses to evaluate null results. All trial-level data, subject-level data, analysis scripts, and experimental files for both experiments are openly available on the Open Science Framework, allowing independent verification and reuse. The study was approved by the Institutional Review Board of Soochow University, informed consent was obtained from all participants, and the work was supported by the National Natural Science Foundation of China and an undergraduate innovation training program at Soochow University.

Looking forward, the authors suggest that the sound-induced enhancement of the non-contact illusion constitutes a promising new paradigm for investigating multisensory processing. Because the effect is behaviorally robust, mechanistically traceable to an identifiable early ERP component, and free from the confounds that complicate stream-bounce designs, it offers researchers a versatile instrument for dissecting when, where, and how the brain integrates sound and sight. Some limitations remain: the design’s contact-duration constraints restricted reaction-time analyses to a single duration condition, and ERP requirements limited the number of participants meeting trial-count criteria in some conditions, pointing toward richer future experiments. Even so, the demonstration that a meaningless beep can tip the brain’s reconstruction of a visual collision toward the conviction that no contact ever occurred is a vivid reminder that perception is not a passive recording of the world. It is an active, multisensory construction, one that sound can quietly rewrite within a fraction of a second.

Subject of Research: Sound-induced enhancement of the non-contact illusion, a cross-modal audiovisual perceptual effect studied with behavioral and ERP measures.

Article Title: A novel cross-modal perceptual effect: Sound-induced increase of the non-contact illusion

Article References: Song, W., Li, X., Guo, Y., & Zhao, S. (2026). A novel cross-modal perceptual effect: Sound-induced increase of the non-contact illusion. Attention, Perception, & Psychophysics, 88(7), Article 183. https://doi.org/10.3758/s13414-026-03332-6

Image Credits: AI Generated

DOI: 10.3758/s13414-026-03332-6

Keywords: non-contact illusion, cross-modal interaction, audiovisual perception, multisensory integration, event-related potential, PD170, sound-induced illusion, visual motion perception, stream-bounce effect, perceptual psychology, ERP, attention perception psychophysics