all participants were individually calibrated to the eye tracker using a 9-point calibration sequence of shrinking red dots in various locations across the screen.
After successful calibration,
participants were given a practice session that procedurally resembled the experiment except that there were three blocks that had 3 learning trials and 1 test trial.
The stimuli in the practice phase were natural kinds (e.g., birds, fish, butterflies) that could be categorized by color and/or shape.