Pupil dilation was recorded at a 50-Hz sampling rate using a Tobii x50 eye-tracker and ClearView software (Tobii, Stockholm, Sweden). Calibration was achieved after net application and before completing the task-switching paradigm, using a 5-point procedure. Analysis of pupil dilation was limited to the first 2500 ms of each trial, that is, the 1500 ms gift/cue presentation and the first 1000 ms following target onset. The 200 ms immediately preceding cue/gift onset (during which a fixation cross was presented) were used as baseline for each trial and pupil dilation was calculated as percent change from this baseline, in order to control for age-related differences in baseline pupil diameter (Chatham et al., 2009 (link)). Measurements for correct trials were averaged into consecutive 60-ms bins. Trials that contained valid data points for less than half of the segment were discarded. Children with at least 5 good trials in each experimental cell were included in the statistical analyses (N = 26 at age 5 and N = 24 at age 10). On average, there were 19 good segments per experimental cell (out of 30) at age 5 and 26 at age 10.
Unless otherwise noted, all measures were analyzed using 3 (Condition: Proactive Impossible, Proactive Possible, Proactive Encouraged) × 2 (Trial Type: No-switch, Switch) × 2 (Age: 5, 10) mixed design ANOVAs2.
Unless otherwise noted, all measures were analyzed using 3 (Condition: Proactive Impossible, Proactive Possible, Proactive Encouraged) × 2 (Trial Type: No-switch, Switch) × 2 (Age: 5, 10) mixed design ANOVAs2.