Distraction by unexpected sounds during passage reading and dynamic scene viewing

Previous research suggests that unexpected sounds can inhibit eye-movements, which may occur due to global suppression of motor actions. If this is the case, then eye-movements should be inhibited across a range of tasks, and the degree of inhibition should be relatively independent from the bottom-up perceptual processes associated with each task. In the present study, we tested whether unexpected novel sounds inhibit eye-movements in two complex and ecologically valid tasks: passage reading and dynamic scene viewing. Participants read short passages from textbooks for comprehension and watched short videos of urban environments for memory recall while their eye-movements were being recorded. On every 5th fixation, a sound was played: this was either a repeated “standard” sine wave tone with a probability of .8 or a “novel” environmental sound with a probability of .2. Unexpected novel sounds led to longer fixation durations compared to the standard sound in both tasks, but the effect was slightly weaker in the dynamic scene viewing task. Follow-up analyses suggested that smooth pursuit eye-movements did not fully explain the attenuation of the effect in the scene viewing task. These results suggest that saccadic inhibition by unexpected sounds can occur in different active vision tasks, but the effect may not be entirely independent of the task dynamics.