Researchers at UC Santa Barbara and the University of Bristol show that the visual system can perform multiple tasks at once without losing speed or accuracy.
Conventional wisdom holds that multitasking impairs mental performance. Yet new research on visual sampling — the rapid sequence of brief glances we use to gather visual information — finds that the brain can simultaneously perform distinct visual functions with remarkable efficiency. A collaboration between scientists at UC Santa Barbara (UCSB) and the University of Bristol demonstrates that foveal analysis (detailed inspection at the center of gaze) and peripheral selection (choosing where to look next) operate in parallel without a trade-off in time or accuracy.
“Human vision is surprisingly constrained,” said Miguel Eckstein, professor in the Department of Psychological and Brain Sciences at UCSB. “We see sharply only within a small region around the point we’re looking at.” That high-acuity region is the fovea, a small depression at the back of the eye responsible for tasks that require fine detail — reading, inspecting faces, or confirming an object’s identity. Everything outside this narrow zone is substantially less clear, which is why we must move our eyes to inspect items of interest.
During everyday searches — locating a specific book on a crowded shelf, finding a prescription bottle in a medicine cabinet, or spotting a friend in a crowd — the brain performs two distinct operations. First, it performs foveal analysis: inspecting the item currently in focus to decide whether it matches the target. Second, it performs peripheral selection: evaluating items in the surrounding visual field to decide where to move the eyes next. How the brain coordinates these two tasks without slowing down or compromising accuracy was the central question of the study.
To investigate, researchers Miguel Eckstein and colleagues Casimir J. H. Ludwig and J. Rhys Davies designed a set of laboratory experiments that separately probed foveal analysis and peripheral selection while varying task difficulty. Participants’ eye movements were recorded with infrared eye-tracking while they made perceptual judgments about foveal stimuli and selected peripheral targets for subsequent saccades. The team introduced temporal perturbations to the stimuli and used computational methods to visualize how information accumulated over time to guide eye movements and judgments.
Traditional models of cognitive multitasking predict a bottleneck: if two tasks compete for shared resources, doing them simultaneously should either slow performance on one or reduce accuracy. If the brain prioritized peripheral selection, foveal judgments should suffer; if it prioritized foveal analysis, peripheral selection should be less reliable. Instead, the UCSB–Bristol experiments produced a different outcome.
The results showed that foveal analysis and peripheral selection proceeded in parallel. Neither process delayed or impaired the other: perceptual judgments at fixation remained accurate, and eye movements toward correct peripheral targets occurred with the same frequency as when each task was performed in isolation. In other words, the two functions appear to be largely independent, operating concurrently without measurable interference in the tested conditions.
This parallel capacity likely reflects the enormous amount of experience humans acquire through daily visual sampling. On average, people make roughly 10,000 eye movements per day, continuously alternating between examining objects closely and scanning the periphery for future targets. That practiced coordination may shape neural systems so that selection and analysis can run simultaneously. Evolutionary pressures requiring vigilance across the visual field while focusing on specific tasks — such as foraging, hunting, or navigating complex environments — may also have favored this functional organization.
“We do not yet know whether this ability is innate, learned early in life, or a combination of both,” Eckstein said. Still, demonstrating that foveal analysis and peripheral selection are parallel, simultaneous, and relatively independent provides a foundation for new research into how the brain coordinates visual attention and eye movements.
Notes about this neuroscience and vision research
Contact: Sonia Fernandez, UCSB
Source: UCSB press release
Image credit: Image adapted from the UCSB press release.
Original research: Casimir J. H. Ludwig, J. Rhys Davies, and Miguel P. Eckstein. “Foveal analysis and peripheral selection during active visual sampling.” Proceedings of the National Academy of Sciences (PNAS). Published online January 2, 2014. DOI: 10.1073/pnas.1313553111.
Keywords: visual sampling, foveal analysis, peripheral selection, eye movements, vision research, UCSB, University of Bristol, PNAS.