Reward History and Multisensory Signals Interact in a Localisation Task.

Previously rewarded stimuli can influence later performance even when they are task-irrelevant, while multisensory stimuli often enhance perceptual salience and speed responses to targets. This study examined how reward history and multisensory stimulus configuration jointly shape behaviour in a speeded localisation task. Participants first learned associations between visual stimuli and high or low reward. In a subsequent test phase, they localised an unrewarded visual target while a previously rewarded distractor appeared in the opposite hemifield. Target and distractor modalities were independently varied between unisensory visual and multisensory audiovisual stimuli. Responses were faster to multisensory than unisensory targets, and high-value distractors slowed responses relative to low-value distractors when both target and distractor were unisensory. However, when targets were multisensory and distractors were unisensory, distractor value no longer influenced response times. Multisensory signals at the distractor produced more complex effects: when the target was multisensory, high-value multisensory distractors slowed responses more than high-value unisensory distractors, whereas when the target was unisensory, high-value multisensory distractors produced less slowing than high-value unisensory distractors. These findings show that reward history and multisensory stimulus configuration interact in shaping target-localisation performance. The observed effects may reflect attentional selection, response selection, or interactions between these processes, but not necessarily attentional selection. To determine this, future designs should disambiguate target location and response.