UCLA

Most laypersons assume that remembering and forgetting occur along a single continuum. That is, to remember is to avoid forgetting. To the contrary however, over 20 years of research suggests that forgetting can actually be incredibly adaptive, and indeed quite essential for the efficient functioning of the memory system. Forgetting serves as an updating mechanism, allowing for the successful retrieval of current information that is relevant, at the expense of irrelevant or outdated information. One very illustrative example of such adaptive forgetting is a phenomenon known as retrieval-induced forgetting (Anderson, Bjork, & Bjork, 1994). While information that is retrieved is strengthened in memory and thus becomes more recallable than it would have been otherwise, related items in competition with that which is retrieved become less recallable. This decrement in recall for related, competing information is referred to as retrieval-induced forgetting.

Investigations of retrieval-induced forgetting typically employ a standard retrieval-practice paradigm that consists of three phases. During the initial learning a phase, a series of category-exemplar pairs, drawn from a number of different categories, are presented to the participant for study (e.g., fruit: orange, drinks: whiskey, trees: elm). Subsequently, during the retrieval-practice phase, a subset of the pairs are retrieved in response to category-plus-two-letter-stem cues (e.g., fruit:or, drinks: wh). After a brief distractor task, participants are prompted to retrieve all of the initially presented pairs in response to category-plus-one-letter stem cues (e.g., fruit; o, drinks:w). This retrieval-practice paradigm creates three types of items: Rp+ items that were retrieved during the retrieval-practice phase (e.g., fruit: orange), related Rp- items that share the same category cue but were not retrieved during retrieval-practice (e.g., fruit: apple), and baseline or Nrp items from nonpracticed categories that did not receive retrieval-practice (e.g., trees: elm). Not surprisingly, Rp+ items that were given retrieval practice after study are recalled better than related Rp- items from the same categories that were not practiced. Interestingly however, relative to nonpracticed items from nonpracticed categories, (i.e. Nrp items), Rp- items are impaired. Said differently, on average, participants recall fewer Rp- items than Nrp items. This decrement in recall for Rp- items relative to Nrp items is referred to as retrieval-induced forgetting.

Such retrieval-induced forgetting is assumed by many to reflect inhibitory mechanisms recruited during retrieval of target items to decrease the accessibility of related, nontarget items. In Chapter 1, I will briefly review the literature on retrieval-induced forgetting.

Recently however, Jonker, MacLeod, and Seli (2013) proposed an alternate account that emphasized the role of context in producing retrieval-induced forgetting. In this framework, the study and retrieval-practice phases are represented as two disparate contexts. While the study context includes all of the studied items – that is, the Rp+, Rp-, and Nrp items – the practice context only contains the Rp+ items. Critically, while the Nrp or baseline items are only present in the study context, the Rp- cues are associated with both the study context and the retrieval-practice context. Thus, at test, participants may search the retrieval practice context first which then makes it more difficult to recall items from the study context. The Nrp cues, however, are only associated with the study context, and are therefore very effective at reinstating the initial study context.

In evidence of this account, Jonker et al. (2013) showed that even restudy practice—which is assumed by the inhibitory account to be insufficient to cause forgetting —can cause forgetting when a mental context change is inserted between study and restudy. In Chapter 2, I present a series of experiments designed to replicate this finding while also testing the possibility that a far mental context change would cause more forgetting than a near mental context change.

An important assumption of the contextual-cuing account is that if only the practice context is reinstated at final test, retrieval-induced forgetting will occur because participants are unable to access Rp- items. In contrast, if the study context is reinstated at test, because all items are available, retrieval-induced forgetting should be eliminated. To test this critical assumption, in Chapter 3, several experiments are presented in which subjects were encouraged to reinstate the appropriate context regardless of whether a given item was practiced or unpracticed. Finally, in Chapter 4, a summary and interim conclusions are given, as well as future directions that may be fruitful in this domain of research.