Two choices good, four choices better: For measuring stereoacuity in children, a four-alternative forced-choice paradigm is more efficient than two
Fig 4
Simulation results for 2-AFC (top) and 4-AFC (bottom).
Each panel depicts the difference between the estimated thresholds and the model thresholds as a function of the model threshold (all in log10 arcsec). The average difference, plotted with open circles, is centred on zero, indicating no bias. Filled triangle symbols represent one standard deviation below and above the average difference. The asterisks show the median (around zero) and the 16th and 84th percentile. That the median and 16th and 84th percentiles respectively overlap with the mean and one SD below and above the mean indicate that the differences follow a normal distribution. The top row shows results for the 2-AFC task for a selection of number of trials (40, 60, and 80 trials). The bottom row shows results for the 4-AFC task for half the number of trials as the 2-AFC task (20, 30, and 40 trials).