Selective spatial attention to competing speakers in azimuth and depth: Evidence from real and virtual environments.

Background and objective: Selective auditory attention enables listeners to focus on a target speaker while suppressing concurrent sounds. To assess the ecological validity of virtual reality for studying spatial attention, the present study investigated cognitive and neural mechanisms in both real and virtual laboratory environments. Method: Participants completed a selective spatial attention task in both real and virtual environments under auditory-only and audio-visual conditions while EEG was recorded. Speech stimuli were presented from different locations in both azimuth and depth. In each trial, two simultaneous speech stimuli originated from different locations. Each stimulus included a target or distractor word (plus visual patterns in the audio-visual condition) followed by a numeral. Participants indicated whether the numeral at the target location was odd or even, ignoring the competing numeral. Results: Performance was slower and less accurate in the virtual environment, with auditory-only stimulation, and in depth-only trials, suggesting slower accumulation of sensory evidence, as confirmed by drift-diffusion modeling. Early sensory ERPs (P1, N1) were largely stable across conditions, whereas P2 amplitudes were modulated by environment, stimulation, and spatial configuration. Spatial configuration also strongly influenced amplitudes of the contingent negative variation, which were largest with azimuth-only stimuli. Importantly, these effects were consistent across environments and largely independent of visual cues and significant cross-environment correlations were observed for all behavioral and neurophysiological measures. Conclusion: These findings suggest that, despite additional perceptual and cognitive demands indicated by reduced performance and slower evidence accumulation, virtual reality captures key mechanisms of selective attention.