ABSTRACT
Temporal acuity is not absolute, but rather is scaled to the reference duration. It is frequently expressed in terms of a coefficient of variation (COV), taken as the difference threshold divided by the point of subjective equality. The COY is sometimes referred to as the Weber fraction, and when this value remains constant, then temporal acuity is said to obey Weber's law, similar to that observed on discrimination tasks for many other perceptual dimensions, including numerosity (e.g., Krueger, 1989, p. 268). The fact that variability scales with duration indicates that the underlying noise is associated with the operation of an internal clock. Nonscalar sources of variability are attributed to other processes such as those associated with starting and stopping the timing process or various decision sources.
