Quantifying accuracy on distance estimation tasks: A Monte Carlo study.

An important aspect of perceptual learning involves understanding how well individuals can perceive distances, sizes, and time-to-contact. Oftentimes, the primary goal in these experiments is to assess participants' errors (i.e., how accurately participants perform these tasks). However, the manner in which researchers have quantified error, or task accuracy, has varied. The use of different measures of task accuracy, to include error scores, ratios, and raw estimates, indicates that the interpretation of findings depends on the measure of task accuracy utilized. In an effort to better understand this issue, we used a Monte Carlo simulation to evaluate five dependent measures of accuracy: raw distance judgments, a ratio of true to estimated distance judgments, relative error, signed error, and absolute error. We simulated data consistent with prior findings in the distance perception literature and evaluated how findings and interpretations vary as a function of the measure of accuracy used. We found there to be differences in both statistical findings (e.g., overall model fit, mean square error, Type I error rate) and the interpretations of those findings. The costs and benefits of utilizing each accuracy measure for quantifying accuracy in distance estimation studies are discussed.

The effects of testing environment, experimental design, and ankle loading on calibration to perturbed optic flow during locomotion.

Calibration is the process by which the execution of actions becomes scaled to the (changing) relationship between environmental features and the actor's action capabilities. Though much research has investigated how individuals calibrate to perturbed optic flow, it remains unclear how different experimental factors contribute to the magnitude of calibration transfer. In the present study, we assessed how testing environment (Experiment 1), an adapted pretest-calibration-posttest design (Experiment 2), and bilateral ankle loading (Experiment 3) affected the magnitude of calibration to perturbed optic flow. We found that calibration transferred analogously to real-world and virtual environments. Although the magnitude of calibration transfer found here was greater than that reported by previous researchers, it was evident that calibration occurred rapidly and quickly plateaued, further supporting the claim that calibration is often incomplete despite continued calibration trials. We also saw an asymmetry in calibration magnitude, which may be due to a lack of appropriate perceptual-motor scaling prior to calibration. The implications of these findings for the assessment of distance perception and calibration in real-world and virtual environments are discussed.