title: Pupil dilation reveals top-down attentional load during spatial monitoring.
abstract: It has long been known that the diameter of human pupil enlarges with increasing effort during the execution of a task. This has been observed not only for purely mechanical effort but also for mental effort, as for example the computation of arithmetic problems with different levels of difficulty. Here we show that pupil dilation reflects changes in visuospatial awareness induced by attentional load during multi-tasking. In the single-task condition, participants had to report the position of lateralized, briefly presented, masked visual targets ("right", "left", or "both" sides). In the multitasking conditions, participants also performed additional tasks, either visual or auditory, to increase the attentional load. Sensory stimulation was kept constant across all conditions to rule out the influence of low-level factors. Results show that event-related pupil dilation strikingly increased with task demands, mirroring a concurrent decrease in visuospatial awareness. Importantly, pupil dilation significantly differed between two dual-task conditions that required to process the same number of stimuli but yielded differed levels of accuracy (difficulty). In contrast, pupil dilation did not differ between two conditions which were equally challenging but differed both in the modality of the dual task (auditory vs. visual) and in the number of stimuli to be attended. We conclude that pupil dilation genuinely reflects the top-down allocation of supramodal attentional resources.
authors.affiliation: Laboratoire Psychologie de la Perception (CNRS UMR 8242), Université Paris Descartes, Paris, France. Electronic address: matteo.lisi@parisdescartes.fr.
authors.forename: Matteo
authors.initials: M
authors.lastname: Lisi
authors.affiliation: Department of Experimental Psychology, Ghent University, Ghent, Belgium.
authors.forename: Mario
authors.initials: M
authors.lastname: Bonato
authors.affiliation: Department of General Psychology and Center for Cognitive Neuroscience, University of Padova, Padua, Italy; IRCCS San Camillo Hospital, Lido Venice, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Zorzi
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001364:Awareness / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Attention; Attentional load; Pupil dilation; Spatial awareness