A solution to the problem of context-dependent recognition memory is presented in terms of the item, associated context, and ensemble (ICE) theory. It is argued that different types of context effects depend on how context information is encoded at both learning and retrieval. Matching associated context in memory and a retrieval cue produces increases in both hit and false alarm rates and may not be accompanied by a change in discrimination. Integrating item and context information in an ensemble and matching ensemble information in memory and a retrieval cue produces context-dependent discrimination. Empirical support for these predictions is presented.

In 3 experiments motivated by the implicit memory literature, the authors investigated the effects of different strengthening operations on the list strength effect (LSE) for explicit free recall, an effect posited by R. M. Shiffrin, R. Ratcliff, and S. E. Clark (1990) to be due to context cuing. According to the one-shot hypothesis, a fixed amount of context is stored when an item is studied for at least 1 or 2 s. Beyond the initial context storage, increases in study time or different orienting tasks do not influence the amount of context that is stored, and thus only spaced repetitions should produce a positive LSE. Consistent with prior findings, spaced repetitions always produced a positive LSE, but increases in depth of processing, study time, and massed repetitions did not. A model implements the one-shot hypothesis, and a role for context storage as a link between episodic and semantic memory is discussed.

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Forgetting is frustrating, usually because it is unintended. Other times, one may purposely attempt to forget an event. A global theory of recognition and free recall that explains both types of forgetting and remembering from multiple list experiments is presented. The critical assumption of the model is that both intentional and unintentional forgetting are often due to contextual interference. Unintentional forgetting is the natural result of contextual changes between study and test. Intentional forgetting is accomplished by a rapid, metacognitively instigated change in mental context that renders to-be-forgotten information relatively inaccessible and renders to-be-remembered information more accessible (L. Sahakyan & C. M. Kelley, 2002). This occurs for both recognition and free recall. Implications for item-method directed forgetting, exclusion recognition, source memory, and encoding operations are discussed.

Empirical tests were conducted on the elevated-attention hypothesis that low-frequency (LF) words are better recognized than high-frequency (HF) words because LF words attract more attention than do HF words (e.g., Glanzer & Adams, 1990). The elevated-attention hypothesis predicts that the hit rate advantage for LF words should be reduced by increases in attentional strain at study. We first tested this prediction in two experiments by varying the amount of experimenter-controlled study time (on the basis of the assumption that a decrease in study time would reduce the amount of resources available for studying a word). The elevated-attention hypothesis was confirmed, but only when words were studied for relatively short durations. This finding led us to formulate an early-phase elevated-attention hypothesis that proposes that more attentional resources are allocated to LF words than to HF words only during the early phase of encoding (which produces the LF hit rate advantage in subsequent recognition) and that the allocation of attentional resources during the late phase of encoding is not greater for LF words than for HF words. An additional empirical test of this revised hypothesis was conducted: Experimenter-controlled study time and the composition of the to-be-remembered pairs of words were varied orthogonally. The results confirmed the early-phase elevated-attention hypothesis.

Atkinson and Shiffrin's (1968) dual-store model of memory includes structural aspects of memory along with control processes. The rehearsal buffer is a process by which items are kept in mind and long-term episodic traces are formed. The model has been both influential and controversial. Here, we describe a novel variant of Atkinson and Shiffrin's buffer model within the framework of the retrieving effectively from memory theory (REM; Shiffrin & Steyvers, 1997) that accounts for findings previously thought to be difficult for such models to explain. This model assumes a limited-capacity buffer where information is stored about items, along with information about associations between items and between items and the context in which they are studied. The strength of association between items and context is limited by the number of items simultaneously occupying the buffer (Lehman & Malmberg, 2009). The contents of the buffer are managed by complementary processes of rehearsal and compartmentalization (Lehman & Malmberg, 2011). New findings that directly test a priori predictions of the model are reported, including serial position effects and conditional and first recall probabilities in immediate and delayed free recall, in a continuous distractor paradigm, and in experiments using list-length manipulations of single-item and paired-item study lists.

According to some theories of recognition memory (e.g., S. Dennis & M. S. Humphreys, 2001), the number of different contexts in which words appear determines how memorable individual occurences of words will be: A word that occurs in a small number of different contexts should be better recognized than a word that appears in a larger number of different contexts. To empirically test this prediction, a normative measure is developed, referred to here as context variability, that estimates the number of different contexts in which words appear in everyday life. These findings confirm the prediction that words low in context variability are better recognized (on average) than words that are high in context variability.In a typical recognition memory experiment, a list of words is studied, and memory is tested subsequently by showing subjects both words that were studied (i.e., targets) and words that were not studied (i.e., foils). The subject's task is to discriminate the targets from the foils. Of course, subjects have encountered words a large number of times in many different contexts prior to the experiment. Hence, the subject's rather daunting task is to discriminate the most recent encounter with a word from all prior encounters.Theories of memory usually address this issue by making a distinction between item and context information (e.g., Anderson & Bower, 1972;Dennis & Humphreys, 2001;Humphreys, Bain, & Pike, 1989;Jacoby, 1991;Maddox & Estes, 1997;McGeoch, 1942;Mensink & Raaijmakers, 1988;Raaijmakers & Shiffrin, 1981;Shiffrin & Steyvers, 1997): Item information represents a studied stimulus (e.g., a word), and context information represents the environment in which the stimulus was encountered. According to these theories, when an item is studied, both item and context information are stored in an episodic trace, and when recognition memory is tested, memory is probed with a retrieval cue consisting of both item and context information. The critical role context plays in the retrieval cue is to restrict the probe to the relevant subset of memory traces (as defined by the task). Those episodic traces that contain context information similar to the retrieval cue might become members of the "activated" subset of memory and contribute information to the recognition decision. Hence, the to-be-remembered encounter with a word can, in principle, be isolated from prior encounters according to the similarity between the context used in the retrieval cue and context information stored in memory.

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