spaced repetitions. Subjects were asked to perform various "orienting tasks", tasks which require the subject to make a simple judgment about the list item (i.e. pleasant or unpleasant, active or passive). Subjects either performed the same task for each occurrence of a word or a different task for each occurrence. If the encoding variability theory were true, then the case of different orienting tasks ought to provide variable encoding, even for massed repetitions, resulting in a higher rate of recall for massed repetitions than would be expected. The results showed no such effect, providing strong evidence against the importance of encoding variability. Study-phase retrieval theory A theory that has gained a lot of traction recently is the study-phase retrieval theory. This theory assumes that the first presentation is retrieved at the time of the second. This leads to an elaboration of the first memory trace. Massed presentations do not yield advantages because the first trace is active at the time of the second, so it is not retrieved or elaborated upon. Greene (1989) proposed a two-factor account of the spacing effect, combining deficient processing and study-phase retrieval accounts. Spacing effects in free recall are accounted for by the study-phase retrieval account. Under the assumption that free recall is sensitive to contextual associations, spaced items are at an advantage over massed items by the additional encoding of contextual information. Thus, the second occurrence of an item in a list reminds the observer of the previous occurrence of that same item and of its previous contextual features. Different contextual information is encoded with each presentation, whereas for massed items, the difference in context is relatively small. More retrieval cues, then, are encoded with spaced learning, which in turn leads to improved recall. Deficient processing According to the deficient processing view, massed repetitions lead to deficient processing of the second presentation—that we simply do not pay much attention to the later presentations (Hintzman et al., 1973). Greene (1989) proposed this to be the case in cued-memory tasks (e.g. recognition memory, frequency estimation tasks), which rely more on item information and less on contextual information. The increased voluntary rehearsal of spaced items makes this deficient processing noticeable. Findings that the spacing effect is not found when items are studied through incidental learning support this account. Retrieval effort hypothesis According to research conducted by Pyc and Rawson (2009), successful but effortful retrieval tasks during practice