Page 39 - It' about time: Studying the Encoding of Duration

Chapter 2 trial an automated drift check was conducted, continuing after participants had successfully fixated within 2° of the center of the fixation dot for 250 ms. If participants failed the automated drift check, the eye tracker was recalibrated. Gaze position was monitored throughout both the adaptation and test phase. Additionally, presentation of the test stimulus was gaze contingent, with failed fixation (deviation >2°) leading to a disappearance of the test stimulus and re- run of the same trial. In total, participants completed 6 blocks each containing 50 trials (300 trials total). This equated to 50 trials for each unique combination of conditions. All measurements were conducted across two 50-min sessions separated by a 15-min break. A 41 B 3 2 Figure 4. Schematic representation of the stimulus display in Experiment 3 (dotted lines for illustrative purposes only). A) For each participant adaptation stimuli were presented at one of the 4 positions. Test stimuli were presented at either the same location, or in the adjacent horizontal and vertical quadrants. This led to three possible presentation conditions: same locations (0°), within-hemifield (11.31°) or between-hemifield (11.31°). B) An example display for a single participant, the outlined circle indicates the adapted location and the white circles show possible test locations. Results & discussion Eyetracking data. The eyetracking signal was stable throughout most of the experiment with only a small percentage of missed samples during stimulus presentation: adaptation presentations (3.94%), top-up presentations (5.42%), and test stimulus presentation (0%). We analyzed the successfully measured samples by calculating the percentage of fixations that fell within 2 degrees of visual angle from the central fixation dot. We found that participants fixated the fixation dot 97.03% (SD: 1.10%) of the time during the presentation of adaptation stimuli, 96.25% (SD: 1.66%) of the time during top-up presentation, 99.79% (SD: 0.28) of the time during the presentation of the test stimulus. 38