Principle #3b – Time. Learning takes time. Time does not cause learning to happen but provides a necessary condition for it to take place. This foundational role of time in learning was well stated by McGeoch (1932) when he said,
Time, in and of itself, does nothing. It contributes, rather, a logical framework in terms of which we can describe the sequence of observed events. Certain spans of it are necessary in order to give other and effective factors a chance to operate, and time, thus, figures largely in scientific description, but not as a factor in causal laws nor is itself active in any way. (p. 359)
There are two important aspects of time in learning. First is the total amount of time required to attain the learning target. Second is the distribution of learning activity within that span of time. Because of mental and physical fatigue, it is generally not feasible to reach a sizable target in one continuous session of practice. Instead, sufficient time must be allowed for the learning target (i.e., the pre-determined change in capacity) to be achieved, and then practice must be distributed within that span of time as necessary to allow for recovery from physical and mental fatigue. Distribution of practice is also necessary because massed, repeated exposure results in temporary automaticity, meaning the activity may be performed without attention. Until firmly established however, this automaticity is fleeting.
 Time is primarily a function of repetition (Principle #3a), or, the duration and frequency of whatever practice models, exercise, or experience (Principle #4) is necessary to effect the desired change in capacity (Principle #2).