Discrimination of speed distributions: sensitivity to statistical properties.

Two experiments examining the ability of human observers to detect differences in the statistical properties underlying velocity distributions were conducted. A four-alternative forced-choice methodology, using four simultaneous velocity distributions, was used in both experiments. In the first experiment the value of one statistical moment (mean, variance, skewness, or kurtosis) was manipulated while the others were held constant. The subjects task was to determine which of four velocity distributions contained the dissimilar value. In the second experiment only the latter three moments were examined. A similar procedure was used, however feedback was given after each trial to maximize observer performance. The results from both experiments indicate that human observers can reliably detect differences in both mean and variance information underlying velocity distributions. The results of this research has important implications for image segmentation and the detection of heading from optic flow.