memory is cued not only based on one’s mental representation of the study item itself, but also of the study context. Since context varies and increasingly changes with time, on an immediate free-recall test, when memory items compete for retrieval, more recently studied items will have more similar encoding contexts to the test context, and are more likely to be recalled. Outside immediate free recall, these models can also predict the presence or absence of the recency effect in delayed free recall and continual-distractor free-recall conditions. Under delayed recall conditions, the test context would have drifted away with increasing retention interval, leading to attenuated recency effect. Under continual distractor recall conditions, while increased interpresentation intervals reduce the similarities between study context and test context, the relative similarities among items remains unchanged. As long as the recall process is competitive, recent items will win out, so a recency effect is observed. Ratio rule Overall, an important empirical observation regarding the recency effect is that it is not the absolute duration of retention intervals (RI, the time between end of study and test period) or of inter-presentation intervals (IPI, the time between different study items) that matters. Rather, the amount of recency is determined by the ratio of RI to IPI (the ratio rule). As a result, as long as this ratio is fixed, recency will be observed regardless of the absolute values of intervals, so that recency can be observed at all time scales, a phenomenon known as time-scale invariance. This contradicts dual-store models, which assume that recency depends on the size of STS, and the rule governing the displacement of items in the STS. Potential explanations either then explain the recency effect as occurring through a single, same mechanism, or re-explain it through a different type of model that postulates two different mechanisms for immediate and long-term recency effects. One such explanation is provided by Davelaar et al. (2005), who argue that there are dissociations between immediate and long-term recency phenomena that cannot be explained by a single-component memory model, and who argues for the existence of a STS that explains immediate recency, and a second mechanism based on contextual drift that explains long-term recency. Related effects In 1977, William Crano decided to outline a study to further the previous conclusions on the nature of order effects, in particular those of primacy vs. recency, which were said to be unambiguous