The Pip-and-Pop Effect in Depth: How Multisensory Stimuli Influence Depth Perception

Multisensory integration is known to facilitate attentional selection, yet its influence on depth perception remains poorly understood, partly because depth has been difficult to manipulate and measure under controlled conditions. Here, we investigated how attentional benefits elicited by the audiovisual integration affect distance perception by adapting the classic pip-and-pop paradigm to immersive virtual reality. Participants ( N = 30) searched for a visual target whose transient colour change occurred either alone or synchronously with a nonspatial auditory stimulus. After identifying the target, participants indicated where they believed it had appeared in three-dimensional space (in terms of laterality, elevation and depth). Across trials, synchronous audiovisual pairing produced two reliable effects. First, participants responded faster when the target event was paired with a tone, replicating the core facilitation associated with the pip-and-pop effect in an immersive three-dimensional setting. Second, audiovisual pairing systematically biased depth perception: targets accompanied by a tone were judged as closer to the observer than identical targets presented without a tone, indicating a consistent underestimation of target distance. Exploratory analyses suggested that performance varied when the target's vertical position (height above the ground) was manipulated and also differed as a function of lateral target position. Together, these findings show that multisensory integration does not only alter the speed of attentional selection but also the perceived distance of a target. This extends pip-and-pop effects from attentional facilitation to spatial perception biases. In particular, it demonstrates that spatially mismatched but temporally synchronous audiovisual events can bias distance estimates in immersive environments.