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Abstract

Humans typically respond faster to multisensory compared to unisensory objects. However, it is not always clear whether this enhancement is caused by multisensory integration or simply the increased probability of initiating a response when parallel sensory pathways are active. Most research on multisensory integration also focuses on simple, reflexive responses, leaving open the question of how it influences more complex cognitive functions. This thesis investigates how spatial and temporal task parameters influence the degree of response enhancement, how to determine whether this enhancement reflects integration, and whether these integration benefits extend to higher-level cognitive functions such as inhibitory control. In a series of experiments, human volunteers made saccadic eye movements toward visual, auditory, or combined audiovisual targets. Using a dedicated laboratory setup that combines audiovisual stimulation with eye movement measurements, we assessed eye movement latency in nine observers across three task configurations: (1) gap & placeholders, (2) no-gap & no-placeholders, and (3) no-gap & placeholders. These manipulations allow us to systematically examine how task context influences the degree of enhancement found in saccadic latency – a measure of neural processing speed. Results showed that task configuration significantly affected the magnitude of multisensory response enhancement, with the no-gap & placeholder-configuration yielding the greatest benefit. Using a predictive model comparison, we confirmed that this enhancement exceeded what would be expected from independent sensory processing alone. In a second experiment with a larger sample of 20 observers, we used an antisaccade task to assess whether faster responses come at the cost of reduced eye movement accuracy. Audiovisual stimuli led to faster antisaccades without impairing directional accuracy, suggesting that multisensory integration can enhance inhibitory control. These findings show that spatiotemporal features strongly influence saccadic multisensory response enhancement, with the occurrence of multisensory integration – marked by responses faster than predicted by parallel processing alone – depending on the task configuration. Furthermore, multisensory integration not only improves latency but can also support higher-level cognitive control. These findings provide a reliable foundation to allow exploration of the underlying mechanisms of multisensory perception and orienting behaviour.