Validation of Gazepoint low-cost eye-tracking and psychophysiology bundle

Figures

• 

  Fig. 1. a Schematic of the Fixation-Saccade task. A blue target appeared and switched from the central dot to each of the peripheral dots. b Schematic of the Pupillary Light Reflex task. Each screen appeared 12 times. Both tasks were repeated twice, once with, and once without, a chinrest. c Illustration of the concepts of accuracy and precision for eye-tracking data. The blue center dot represents the known gaze target, and the pink smaller circles represent gaze locations estimated by the eye-tracker. d Three types of eye-tracker accuracy calculations. AH = Horizontal accuracy for a particular gaze sample. AV = Vertical accuracy for a particular gaze sample. AG/EUCL = Global/Euclidian accuracy for a particular gaze sample. e Illustration of saccade metrics. SE = Starting error. LE = Landing error. Curvature = Median of all individual αi angles between each sample point and the straight line connecting the start and end point of the saccade

• 

  Fig. 2. a Average error of the accepted calibration in degrees of visual angle. The shaded part indicates average accuracy stated by the manufacturer (0.5–1 degrees of visual angle). b The number of calibration attempts before the calibration was accepted. Each participant went through the calibration twice in each condition. c Distribution of the inter-sample times grouped in 0.0001 s (0.1 ms) bins in the chinrest condition, d and the no-chinrest condition. Different colors represent different participants (N = 13). The dashed line on the left indicates the expected inter-sample time based on the eye-tracker’s sampling rate (150 Hz), and the dashed line on the right indicates the duration of two consecutive samples

• 

  Fig. 3. a Estimated gaze locations at each target location (individual gaze samples plotted). b Estimated gaze locations at each target dot location (mean fixation positions plotted). c Vertical, d horizontal, and e global accuracy in degrees of visual angle for each condition (chinrest, no-chinrest) and target dot location in the Fixation-Saccade task. The shaded part indicates average accuracy indicated by the manufacturer (0.5–1 degrees of visual angle). Colored dots represent participants’ accuracy in each iteration of target location, while the black dot and error bars represent means and 95% CIs

• 

  Fig. 4. a, b Pupillary light reflex in both chinrest and no-chinrest conditions. Dark-colored time section (from – 5 to 0 s) and dark boxplot indicate pupil dilation during the black screen, while light-colored time section (from 0 to 5 s) and light boxplot indicate pupil constriction during the white screen. Dashed line in graph A indicates the switching point from black to white screen, while the dotted lines mark the baseline period used for calculating baseline pupil size. c, d Main sequence of saccadic eye movements (r = .288, p < .001; r = .420, p < .001). Each colored line represents a slope for each individual participant, while the black line represents the slope across participants. Jittered points presented in the background represent individual saccades

• 

  Fig. 5. Saccade trajectories from the central target to each peripheral target. Each graph shows saccade trajectories of a different participant (N = 13; pix = pixel)

• 

  Fig. 6. Schematics of Experiment 2

• 

  Fig. 7. Illustration of the elements of a heartbeat used to compute heart rate and heart rate variability. RR-interval (or inter-beat interval - IBI) is the time difference between successive heartbeats. NN-interval is a normalized RR-interval in which artefacts have been removed

• 

  Fig. 8. Density plots for accuracy (a), precision (b), and data loss (c). Frequency of fixations, saccades, and data loss for each trial and participant (d). Data represents the density of every single observation for every participant for each trial

• 

  Fig. 9. Self-perceived arousal in response to emotional stimuli correlated with pupil size (a) as did stimulus luminance (b). c The time course of pupil response by high and low arousal stimuli (split for visualization only). Individual lines represent individual participants average pupil trace

• 

  Fig. 10. a–d Scatter plots for raw averages of the skin conductance signal across the Gazepoint biometrics (GPB) and BIOPAC MP160 systems. e–f Scatter plots for correlations of computed heart rate from Gazepoint biometrics system and BIOPAC MP160 ECG. Left plots show data aggregated by participant, and right plots show data for all trials and participants. Each color and line represent a single participant, each dot represents a single trial. *** p < .001

• 

  Fig. 11. Comparison plots of heartbeat data from the Gazepoint biometrics (GBP) and BIOPAC MP160 systems. a and b show a representative participant’s raw recording of pulse (GPB; A) and electrocardiogram (BIOPAC MP160; B) data. c and d show derived heart rate variability metrics for the same participant across the two devices (C = GPB, D = BIOPAC). e and f show point-care plots for the inter-beat-interval (IBI) for all participants. Each color denotes a single participant, each dot denotes a single RR (peak-to-peak) duration