Linear and rotation motion aftereffects as a function of inspection duration

Subjects rated the strength of linear and rotary motion aftereffects (MAEs) on an eleven point scale. Inspection durations ranged from 30 to 180 sec in 30 sec steps. In Expt 1, trials using a single inspection duration were spaced at least 22 hr apart to minimize the possibility of interactions between adapting stimuli and long lasting aftereffects. In Expt 2, a counterbalanced sequence of inspection durations was completed in a single session. Total duration of the MAE and durations of the decay phase and tail were measured directly. The decay time constant (DTC), the time it takes for rated strength of the MAE to drop to 1/e of its initial value, was calculated from a line fit to a semilog plot of the ratings during the decay phase. The DTC is inversely related to the decay rate which is indexed by the slope of this line. In both experiments, the duration and DTC increased, and decay rate decreased, with increasing inspection duration for both rotary and linear MAEs. This finding replicates the results for linear MAEs and extends them to rotation MAEs. There were no discernible differences between the two types of MAEs. When the trials were spaced, the total duration increased with the square root of inspection duration. The DTC did not follow the square root rule over the entire range but appeared to approximate it for inspection durations of 90 sec and above. When trials were massed, the square root rule did not appear to apply at all.