Behavioural and neuronal insights into multisensory combination of unpracticed cues.

Effective decision-making requires integrating multiple information sources, weighted by their reliability and context. While classic studies show near-optimal cue combination with well-learned signals and extensive feedback, everyday choices often rely on unfamiliar or cross-modal cues without such training. We examined cue combination under these conditions using an online perceptual estimation task in large and diverse participant cohorts. Participants combined unpracticed cues, including visual motion direction, spatial visual information, and auditory location, with minimal feedback and occasional cue conflict. Integration strategies varied with age and self-reported ADHD or Autism. Visual cues were combined near-optimally, whereas audio-visual combinations exhibited winner-take-all behaviour, typically but not always favouring the more reliable cue. To test the generality of these findings, we used electrical microstimulation in non-human primates, targeting unimodal or cross-modal association areas. Stimulation of visual cortex was integrated with sensory motion cues, while stimulation of prefrontal cortex promoted winner-take-all choices. These findings suggest universal circuit-level distinctions between within- and across-modality integration, with deviations potentially diagnostic for neuropsychiatric conditions.