Spacing effect
（重定向自Distributed Learning）
The spacing effect is a desirable difficulty phenomenon that when repeatedly reviewing learned information spaced out over time makes these items easier to remember. This effect is achieved through spaced presentation rather than repeatedly studied in a short span of time also known as massed presentation. Practically, this effect suggests that "cramming" (intense, last-minute studying) the night before an exam is not likely to be as effective as studying at intervals in a longer time frame. Important to note, however, is that the benefit of spaced presentations does not appear at short retention intervals, in which massed presentations tend to lead to better memory performance.