Fig 1.
Experimental paradigm of Experiments 1, 2, and 3.
a. Participants fixated on the red dot and remembered the location of the blue memory cue. After a variable retention interval the dot jumped either to the right or left, signaling that a saccade had to be executed. Once a saccade was detected, the red saccade target could move backward, forward, or remain in place. After 250 ms saccade target was removed, signaling that a response had to be made. In Experiment 1 a probe appeared. Participants had to indicate with a key press if this probe was located to the left or to the right of the memorized location. In Experiment 2 a mouse cursor appeared and participants had to click on the memorized location. In Experiment 3 a localization eye movement had to be executed to the remembered location. b. Overview of all the possible memory cue locations (blue) in the right hemifield. The red fixation dot indicates the fixation location. The black dots indicate the possible saccade target location, while the gray dots indicate the location of both a backward and forward displaced saccade target.
Fig 2.
Mean psychometric curves for backward, forward and no displacement conditions in Experiment 1.
Probe location is indicated on the x-axis. The dots represent the mean proportion of forward responses in the no displacement (green), backward (red), and forward (blue) condition. The solid vertical line indicates the correct memory location in the three conditions. The dashed vertical lines indicate the displacement size of the saccade target in the ‘backward’ and ‘forward’ condition. The horizontal grey line indicates chance level. The perceptual null location (PNL), the probe location for which there was an equal number of forward and backward responses, is located at the intersection of the psychometric curve with this line.
Fig 3.
Left: Mean localization responses in backward, forward and no displacement conditions. The horizontal distance is plotted on the x-axis. The error bars represent 95% within-subject confidence intervals. The solid vertical line indicates the veridical memory location. The dashed vertical lines indicate the displacement size of the saccade target in the backward and forward displacement conditions, respectively. Right: Population density plot of the localization responses relative to veridical location of the memorized stimulus in backward, forward and no displacement. The solid vertical lines indicate the displacement of the saccade target in the backward, no displacement, and forward conditions, respectively.
Fig 4.
Left: Mean localization responses in backward, forward and no displacement conditions. Horizontal distance is plotted on the x-axis. The error bars represent 95% within-subject confidence intervals. The solid vertical line indicates the veridical memory location. The dashed vertical lines indicate the displacement size of the saccade target in the backward and forward displacement conditions, respectively. Right: Population density plot of the localization responses relative to veridical location of the memorized stimulus in backward, forward and no displacement. The solid vertical lines indicate the displacement of the saccade target in the backward, no displacement, and forward conditions, respectively.
Fig 5.
Target displacement bias for fast and slow saccades.
The mean effect of target displacement (forward and backward) as a percentage of the total size of displacement, for fast (red) and slow (blue) localization saccades in Experiment 3. Latencies indicate the average interval between landing of the first saccade and start of the localization saccade in the corresponding time bin. The error bars represent 95% confidence intervals.
Fig 6.
Experimental paradigm of Experiment 4.
a. Participants fixated on the red dot and remembered the location of the blue memory cue. After a variable retention interval the dot jumped either to the right or left, signaling that a saccade had to be executed. Once a saccade was detected, the red saccade target could move backward, forward, or remain in place. 150 ms after saccade landing the target was removed, signaling that a localization eye movement had to be executed to the remembered location. b. Overview of the possible memory cue locations (blue) for a rightward saccade. The red fixation dot with error bars indicates the possible fixation locations relative to the saccade target, corresponding to saccades between 9 and 11 visual degrees. The black dot indicates the saccade target location, while the gray dots indicate the location of both a backward and forward displaced saccade target.
Fig 7.
Left: Mean localization responses in backward (red), forward (blue) and no displacement (green) conditions. Horizontal cue location is plotted on the x-axis. The error bars represent 95% within-subject confidence intervals. The horizontal solid green line indicates the veridical memory location. The horizontal dashed lines on top and at the bottom of the figure indicate the displacement size of the saccade target in the backward (red) and forward (blue) displacement conditions, respectively. Right: For comparison; mean localization responses in backward (red), forward (blue) and no displacement (green) conditions in Experiment 1, 2, and 3. In these experiments the memory cue was presented between 2.5 and 4.5 degrees past the saccade target.
Fig 8.
Target displacement bias for fast and slow saccades.
The mean effect of target displacement (Forward and Backward) as a percentage of the total size of displacement, at every cue location for fast (red) and slow (blue) localization saccades in Experiment 4. Latencies indicate the average interval between target offset and start of localization saccades in the corresponding time bin. The non-separated data is plotted in light grey. The error bars represent 95% confidence intervals.