Editing Spacing effect (section)

=== Semantic priming ===
Research has shown reliable spacing effects in cued-memory tasks under incidental learning conditions, where [[semantic analysis (knowledge representation)|semantic analysis]] is encouraged through [[orienting tasks]] (Challis, 1993; Russo & Mammaralla, 2002). Challis found a spacing effect for target words using a frequency estimation task after words were incidentally analyzed semantically. However, no spacing effect was found when the target words were shallowly encoded using a graphemic study task. This suggests that [[semantic priming]] underlies the spacing effect in cued-memory tasks. When items are presented in a massed fashion, the first occurrence of the target semantically primes the mental representation of that target, such that when the second occurrence appears directly after the first, there is a reduction in its semantic processing.  Semantic priming wears off after a period of time (Kirsner, Smith, Lockhart, & King, 1984), which is why there is less semantic priming of the second occurrence of a spaced item. Thus on the semantic priming account, the second presentation is more strongly primed and receives less semantic processing when the repetitions are massed compared to when presentations are spaced over short lags (Challis, 1993). This semantic priming mechanism provides spaced words with more extensive processing than massed words, producing the spacing effect.

From this explanation of the spacing effect, it follows that this effect should not occur with nonsense stimuli that do not have a [[semantic representation]] in [[memory]]. A number of studies have demonstrated that the semantically based repetition priming approach cannot explain spacing effects in [[recognition memory]] for stimuli such as unfamiliar faces, and non-words that are not amenable to semantic analysis (Russo, Parkin, Taylor, & Wilks, 1998; Russo et al., 2002; Mammarella, Russo, & Avons, 2005). Cornoldi and Longoni (1977) have even found a significant spacing effect in a [[forced-choice recognition memory]] task when nonsense shapes were used as target stimuli. Russo et al. (1998) proposed that with cued memory of unfamiliar stimuli, a short-term perceptually-based repetition priming mechanism supports the spacing effect. When unfamiliar stimuli are used as targets in a cued-memory task, memory relies on the retrieval of structural-perceptual information about the targets. When the items are presented in a massed fashion, the first occurrence primes its second occurrence, leading to reduced perceptual processing of the second presentation. Short-term repetition-priming effects for nonwords are reduced when the lag between prime and target trials is reduced from zero to six (McKone, 1995), thus it follows that more extensive perceptual processing is given to the second occurrence of spaced items relative to that given to massed items. Hence, nonsense items with massed presentation receive less extensive perceptual processing than spaced items; thus, the retrieval of those items is impaired in cued-memory tasks.

Congruent with this view, Russo et al. (2002) demonstrated that changing the [[font]] in which repeated presentations of nonwords were presented reduced the short-term perceptual priming of those stimuli, especially for massed items. Upon a recognition memory test, there was no spacing effect found for the nonwords presented in different fonts during study. These results support the hypothesis that short-term [[Semantic priming#Perceptual and conceptual priming|perceptual priming]] is the mechanism that supports the spacing effects in cued-memory tasks when unfamiliar stimuli are used as targets.  Furthermore, when the font was changed between repeated presentations of words in the study phase, there was no reduction of the spacing effect. This resistance to the font manipulation is expected with this two-factor account, as semantic processing of words at study determines performance on a later memory test, and the font manipulation is irrelevant to this form of processing.

Mammarella, Russo, & Avons (2002) also demonstrated that changing the orientation of faces between repeated presentations served to eliminate the spacing effect. Unfamiliar faces do not have stored representations in memory, thus the spacing effect for these stimuli would be a result of perceptual priming. Changing orientation served to alter the physical appearance of the [[stimulus (physiology)|stimuli]], thus reducing the perceptual priming at the second occurrence of the face when presented in a massed fashion. This led to equal memory for faces presented in massed and spaced fashions, hence eliminating the spacing effect.