Steven M. Smith

Environmental context and human memory

Five experiments examined the effects of environmental context on recall and recognition. In Experiment 1, variability of input environments produced higher free recall performance than unchanged input environments. Experiment 2 showed improvements in cued recall when storage and test contexts matched, using a paradigm that unconfounded the variables of context mismatching and context change. In Experiment 3, recall of categories and recall of words within a category were better for same-context than different-context recall. In Experiment 4, subjects given identical input conditions showed strong effects of environmental context when given a free recall test, yet showed no main effects of context on a recognition test. The absence of an environmental context effect on recognition was replicated in Experiment 5, using a cued recognition task to control the semantic encodings of test words. In the discussion of these experiments, environmental context is compared with other types of context, and an attempt is made to identify the memory processes influenced by environmental context.

Environmental context-dependent memory: A review and meta-analysis

To address questions about human memory’s dependence on the coincidental environmental contexts in which events occur, we review studies of incidental environmental context-dependent memory in humans and report a meta-analysis. Our theoretical approach to the issue stems from Glenberg’s (1997) contention that introspective thought (e.g., remembering, conceptualizing) requires cognitive resources normally used to represent the immediate environment. We propose that if tasks encourage processing of noncontextual information (i.e., introspective thought) at input and/or at test, then both learning and memory will be less dependent on the ambient environmental contexts in which those activities occur. The meta-analysis showed that across all studies, environmental context effects were reliable, and furthermore, that the use of noncontextual cues during learning (overshadowing) and at test (outshining), as well as mental reinstatement of appropriate context cues at test, all reduce the effect of environmental manipulations. We conclude that environmental context-dependent memory effects are less likely to occur under conditions in which the immediate environment is likely to be suppressed.

Background Music and Context-Dependent Memory

Two experiments demonstrated the use of background sound for inducing context-dependent memory. If a list of words was presented with sound in the background (instrumental music or white noise), then recall tested 48 hr later was better and forgetting was less if the acoustic background was reinstated rather than changed or removed. If learning occurred with quiet background conditions, recall performance was the same whether testing took place with quiet, music, or white noise in the background. The results imply that context-dependent memory caused by background sound is the beneficial result of contextual cuing rather than a deleterious effect caused by the distractions of a new background sound during testing.

Enhancement of recall using multiple environmental contexts during learning.

Distributing the presentation of sublists of words into multiple learning rooms produced better free recall scores than a single learning room condition for subjects who were given a comprehensive recall test in a new environment. No such effects occurred on recognition or list differentiation tests in Experiment 2, implying a retrieval explanation rather than one relying upon learning or list differentiation effects. Experiment 3 found that the contextual dependence of recall li.e., recall tested in a learning context is better than recall tested in a new context was nullified by using multiple learning rooms, rather than a single room for input. The data are consistent with an explanation that states that the multiple learning rooms become associated with the different sublists during learning and subsequently act as memory landmarks that guide the course of retrieval.

Environmental context-dependent recognition memory using a short-term memory task for input

Although many studies have demonstrated that recall is better when tested in the learning environmental context (EC) than in a new EC, almost all of the studies have failed to find EC-dependent memory when recognition was used to measure memory. Evidence of EC-dependent recognition, however, was found in the three experiments of the present study, in which an incidental short-term memory task was used for input of learned material. The results suggest that type of processing during input is a predictor of context-dependent recognition; material studied for a long-term memory test is not susceptible to background context effects, whereas material merely maintained for a short-term memory test is more apt to lead to EC-dependent recognition.

The roles of associative responses at study and semantically guided recollection at test in false memory: the Kirkpatrick and Deese hypotheses

False recall is found for semantically related words that are not presented on both categorized and associatively structured study lists. Four experiments provide evidence that the associative list method produces false memories because of semantic processes involved in studying list words (the Kirkpatrick hypothesis), but that false memories produced by categorized lists occur because of the use of semantic knowledge at test (the Deese hypothesis). In a free association task, words from associative lists, but not categorized lists, tended to evoke critical words as responses, indicating that our categorized list words have low associative strength to critical nonpresented items. Studying those associative lists, but not the categorized ones, produced indirect priming effects in stem completion. Critical nonpresented words from categorized lists showed a priming effect only when participants were instructed at test to try to complete stems with studied list words (i.e., stem cued-recall). The results highlight important differences between categorized and associative list methods, and indicate that false memories can be caused by semantic processes that occur at the time of a memory test.

Memory blocks in word fragment completion caused by involuntary retrieval of orthographically related primes.

Seven experiments showed that word fragments are not solved as well following prior exposure to orthographically similar primes (e.g., ANALOGY as a prime for A_L__GY) relative to orthographically dissimilar primes (e.g., UNICORN). This blocking effect was influenced by the morality (auditory vs. visual) of the primes but not by the depth to which they were processed. This blocking effect occurred even when participants were informed about it and told to try to avoid remembering the primes, and it was not affected by the proportion of test fragments for which the orthographic primes were correct versus incorrect answers. The results have implications for theories concerned with unconscious mechanisms that underlie memory blocking and blocks to creative problem solving.

Incubated reminiscence effects

Reminiscence, the recall of material that was not successfully recalled on a previous attempt, was examined in three experiments as a function of the intertest (incubation) interval. Incubation intervals inserted between successive recall tests resulted in increased reminiscence, but the effect was seen primarily in the first retested minute. Neither the duration of the initial test (1–4 mm), nor the incubation activity (maze problems vs. rest) affected this incubated reminiscence effect. The results support models in which recall tests cause output interference, but incubation intervals reduce it.

Category structure and created memories

Cued recall of categorized lists was used to examine effects of category structure on the creation of false memories. In three experiments, category members that had not been presented on studied categorized lists were nonetheless recalled by participants. Delaying the category cued recall test (Experiment 1) and priming category members that had been omitted from target lists (Experiment 3) increased the frequency of false recall. All three experiments showed that nonpresented category members that were higher in output dominance were more frequent intrusions. The typicality of category members, however, did not uniquely contribute to the predictability of false recall (or accurate recall) once the contribution of output dominance was taken into account, suggesting that item accessibility (related to output dominance) may be more instrumental than item distinctiveness (related to typicality) in causing certain types of false recall. The results show that created memories in category cued recall are strongly biased by prior category knowledge and can be predicted by the graded structure of categories, particularly in terms of the output dominance of category instances.

A comparison of two techniques for reducing context-dependent forgetting

Recall is poorer when tested in a new environment than when tested in the original learning context. Two techniques for reducing this context-dependent forgetting were compared. One technique involved instructing subjects to recall their learning room(s), and the other attempted to establish multiple environmental retrieval cues by presenting lists in multiple rooms rather than all in the same room. Subjects were given three word lists to study in one or three rooms. All subjects were given a free-recall test in a new room, and half were asked to use remembered environmental context (EC) information to facilitate word memory. Multiple input contexts benefited only subjects who were uninstructed in the use of EC cues. Subjects given EC-recall instructions, however, recalled somewhat less in the three-room condition than in the one-room condition. The facilitative effects of the two techniques were not additive: EC-recall instructions benefited only one-room subjects. The results suggest that both EC-recall instructions and multiple learning contexts induce subjects to use contextual retrieval cues that are otherwise not spontaneously utilized, and that the greater the number of context cues stored in memory, the less accessible those cues become.