spacing effect
a cognitive phenomenon in which distributing to-be-learned information across time in short, interrupted study sessions leads to better long-term retention than continuous, massed sessions. In other words, distributed practice is more beneficial than massed practice. For example, a student preparing for a Spanish vocabulary exam on Thursday would remember more by studying the Spanish–English word pairs during brief sessions (e.g., 1 hour each) on consecutive prior days (e.g., Monday, Tuesday, and Wednesday) than by cramming study into a single session in one day. The spacing effect has been demonstrated with a wide range of learning paradigms, materials, and participants, but the precise mechanisms underlying it remain unclear. Various explanations have been offered, such as the consolidation theory, which proposes that people notice repetitions of items and create a second representation of the item when they encounter it again; the
deficient processing theory, which suggests that people pay more attention to spaced repetitions of an item because the item is thus not as active in memory; the encoding variability theory, which suggests that the contextual information stored with an item varies over time, so that a greater variety of information is stored with spaced presentations, resulting in multiple (or stronger) retrieval routes; and the study-phase retrieval theory, which states that people notice repetitions of items and retrieve the earlier presentation of an item when they encounter it again. Also called distributed-practice effect. See also lag effect; primacy effect; recency effect. [first described in 1885 by Hermann Ebbinghaus]