Microsaccades during high speed continuous visual search.

Jacob G Martin,Maximilian Riesenhuber,Charles E Davis,Simon J Thorpe

doi:10.16910/jemr.13.5.4

Jacob G Martin, Maximilian Riesenhuber + Show 2 more

Open Access

https://doi.org/10.16910/jemr.13.5.4

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Abstract

Here, we provide an analysis of the microsaccades that occurred during continuous visual search and targeting of small faces that we pasted either into cluttered background photos or into a simple gray background. Subjects continuously used their eyes to target singular 3-degree upright or inverted faces in changing scenes. As soon as the participant’s gaze reached the target face, a new face was displayed in a different and random location. Regardless of the experimental context (e.g. background scene, no background scene), or target eccentricity (from 4 to 20 degrees of visual angle), we found that the microsaccade rate dropped to near zero levels within only 12 milliseconds after stimulus onset. There were almost never any microsaccades after stimulus onset and before the first saccade to the face. One subject completed 118 consecutive trials without a single microsaccade. However, in about 20% of the trials, there was a single microsaccade that occurred almost immediately after the preceding saccade’s offset. These microsaccades were task oriented because their facial landmark targeting distributions matched those of saccades within both the upright and inverted face conditions. Our findings show that a single feedforward pass through the visual hierarchy for each stimulus is likely all that is needed to effectuate prolonged continuous visual search. In addition, we provide evidence that microsaccades can serve perceptual functions like correcting saccades or effectuating task-oriented goals during continuous visual search.

Highlights

During active visual search, humans often make high velocity eye-movements called saccades to target variousReceived November 15, 2018; Published June 28, 2020
We were interested in finding out whether microsaccades occurred during continuous visual search
Do the serve any perceptual function? In addition, are microsaccades critical to the success of a continuous search process? If they occur, is there any perceptual function to them or not? To answer these questions, we analyzed the properties of microsaccades that occurred during a continuous visual search task for small faces

Summary

Introduction

Humans often make high velocity eye-movements called saccades to target various. Received November 15, 2018; Published June 28, 2020. When saccades are involuntary and smaller than around 1 degree of visual angle, these ballistic eye movements are typically called "microsaccades." A recent review of scientific evidence collected over a period of more than 60 years argued that microsaccades “are necessary to achieve continual perception during fixation” and “contribute uniquely to visual processing by creating strong transients in the visual input stream. Microsaccades can play an important role in human visual perception When saccades are involuntary and smaller than around 1 degree of visual angle, these ballistic eye movements are typically called "microsaccades." A recent review of scientific evidence collected over a period of more than 60 years argued that microsaccades “are necessary to achieve continual perception during fixation” and “contribute uniquely to visual processing by creating strong transients in the visual input stream. (Rolfs, 2009).” microsaccades can play an important role in human visual perception

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