Saccadic undershoot is not inevitable: saccades can be accurate.

Area of Science:

• Oculomotor control
• Human visual perception

Background:

• Saccades are rapid eye movements crucial for visual exploration.
• Typically, saccades reach 90% of a target, with a corrective saccade completing the movement.
• The range effect describes a deviation from this norm, where saccade endpoints vary based on target set positions.

Purpose of the Study:

• To confirm the range effect using advanced methodologies.
• To investigate the impact of concurrent visual discrimination tasks on the range effect.
• To analyze the characteristics of corrective saccades associated with the range effect.

Main Methods:

• Utilized high-precision eye-tracking to measure saccade endpoints.
• Introduced a visual discrimination task alongside target presentation.
• Recorded latencies and accuracy of corrective saccades.

Main Results:

• Confirmed the range effect: saccades overshot near targets and undershot far targets.
• Observed a rapid establishment of the range effect within a few trials when a visual task was added.
• Found no difference in corrective saccade latencies between overshoots and undershoots.
• Demonstrated that centripetal saccades were more accurate than centrifugal saccades.

Conclusions:

• The range effect is a robust phenomenon in saccadic eye movements.
• Concurrent visual tasks can modulate and rapidly enhance the range effect.
• The accuracy of corrective saccades suggests that undershooting is not an unavoidable consequence of the range effect.