Imagery encoding effects on memory in the DRM paradigm: A test of competing predictions

Does context matter for memory? Testing the effectiveness of learning by imagining situated interactions with objects

Mounting evidence supports the efficacy of mental imagery for verbal information retention. Motor imagery, imagining oneself interacting physically with the object to be learned, emerges as an optimal form compared to less physically engaging imagery. Yet, when engaging in mental imagery, it occurs within a specific context that may affect imagined actions and consequently impact the mnemonic benefits of mental imagery. In a first study, participants were given instructions for incidental learning: mental rehearsal, visual imagery, motor imagery or situated motor imagery. The latter, which involved imagining physical interaction with an item within a coherent situation, produced the highest proportion of correct recalls. This highlights memory's role in supporting situated actions and offers the possibility for further developing the mnemonic potential of embodied mental imagery. Furthermore, item-level analysis showed that individuals who engaged in situated motor imagery remembered words primarily due to the sensorimotor characteristics of the words' referent. A second study investigating the role of inter-item distinctiveness in this effect failed to determine the extent to which the situational and motor elements need to be distinctive in order to be considered useful retrieval cues and produce an optimal memory performance.

Imagination Reduces False Memories for Everyday Action Sentences: Evidence From Pragmatic Inferences

Human memory can be unreliable, and when reading a sentence with a pragmatic implication, such as "the karate champion hit the cinder block," people often falsely remember that the karate champion "broke" the cinder block. Yet, research has shown that encoding instructions affect the false memories we form. On the one hand, instructing participants to imagine themselves manipulating the to-be-recalled items increase false memories (imagination inflation effect). But on the other hand, instructions to imagine have reduced false memories in the DRM paradigm (imagination facilitation effect). Here, we explored the effect of imaginal encoding with pragmatic inferences, a way to study false memories for information about everyday actions. Across two experiments, we manipulated imaginal encoding through the instructions given to participants and the after-item filler task (none vs. math operations). In Experiment 1, participants were either assigned to the encoding condition of imagine+no filler; pay attention+math; or memorize+math. In Experiment 2, the encoding instructions (imagine vs. memorize) and the filler task (none vs. math) were compared across four separate conditions. Results from the two experiments showed that imagination instructions lead to better memory, by showing a higher proportion of correct responses and better performance in a memory benefit index. Similarly, a significant reduction of false memories was observed across both experiments, even though a complementary Bayesian analysis only supported this conclusion for Experiment 1. The findings show that imaginal encoding improves memory, suggesting the engagement of a distinctiveness heuristic and source-monitoring process.

Does Test Type Influence False Recognition in the DRM Paradigm? Comparison of the Yes/No Recognition Test and Two-Alternative Forced-Choice Test

Studies attempting to identify the mechanisms that are responsible for the level of false recognition in the DRM paradigm usually apply a manipulation during encoding. The main aim of the studies reported here was to investigate the within- and between-participant effects of a testing method on memory performance using a standard yes/no recognition test and a 2-alternative forced-choice recognition test (2FC). To allow a direct comparison of the 2 testing methods, a 2FC test containing similar items as a typical yes/no test in the DRM paradigm was elaborated on in the pilot study. Moreover, 2 methods of data calculation were used: comparing rates of hit and false alarms with critical lures and with unstudied and unrelated items between the 2 tests and comparing measures of sensitivity (d’) derived from signal detection theory. Both experiments showed a lower false alarm rate to critical lures and higher hit rate in a 2FC test as compared with a yes/no test, depicting a typical mirror effect. A within-participant design (Experiment 1) also showed that this increased accuracy of a 2FC test diminished when memory performance was expressed in terms of a sensitivity measure, which may suggest that similar processes are used during these 2 retrieval methods. A similar analysis performed for a between-participants design (Experiment 2) revealed that a 2FC test was less susceptible to associative memory distortions, but the quality of memory (“remember/know” judgments) remained similar for both tests.

When do pictures reduce false memory?

An important discovery in false-memory research is Israel and Schacter's (Psychonomic Bulletin & Review, 4, 577-581, 1997) finding that presenting pictures at study relative to words alone reduces false memory in the DRM paradigm, a result that has been replicated many times. The standard interpretation is that memory for visual processing of the pictures can be used to reject the critical distractors, which were not explicitly present at study. Beginning from the empirical observation that the pictures used by Israel and Schacter are not consistently labelled with the DRM word they are supposed to represent, we present a series of four studies designed to determine if it is the presentation of pictures or the mismatch between the pictures and the words that reduces false memory. The results across the four experiments demonstrate that picture presentation at study is neither necessary nor sufficient to reduce false memory in the DRM and the categorical associate paradigms. However, we discuss other studies in which picture processing clearly is responsible for reduction of false alarms and note that these studies use study materials and memory tests that are different from the DRM and categorical associate paradigms in that critical lures are externally provided rather than generated. We speculate that the effectiveness of memory for visual processing for reducing false memory may depend on the source of the false memory, but this remains for future research.

False memories and the DRM paradigm: effects of imagery, list, and test type

Several researchers have reported that instructing participants to imagine items using the Deese-Roediger-McDermott (DRM) paradigm lowers false memory rates (Foley, Wozniak, & Gillum, 2006). However, other researchers have found that imagery does not always lower false memory rates (Robin, 2010), and investigators have examined the effects of imagery manipulation on semantic but not phonological lists. In the present study, we presented 102 participants with semantic and phonological DRM lists, followed by a free recall test and final recognition test. Some participants received instructions to imagine list items during the study phase to facilitate memory, and others were simply told to remember list items. Imagery instructions enhanced correct memories and further suggested a trend for decreased false memories. A test type by list type interaction also emerged, with phonological lists eliciting higher false memories at recall, and semantic lists eliciting higher false memories at recognition. Directions for future research are discussed.

Timing does matter: examining imagery's impact on the temporal origins of false beliefs

In the current study imagination inflation effects were revisited, giving special attention to decreases in confidence ratings following imagery. Reexamining false beliefs, 151 participants were instructed to rate their confidence that they experienced specific childhood events before and after imagery. No significant imagery effects emerged when examining differences in confidence ratings. However, imagery differentially enhanced (26.27%) and diminished (15.45%) belief ratings for specific events. Content analysis of participants' imagery descriptions revealed that only diminished false beliefs were distinguishable from genuine belief accounts, containing less affective and contextual detail as well as fewer words, but remaining comparable in the presence of cognitive operations. These findings suggest that deflation effects provide a route to studying the potentially positive impact of imagery on false beliefs. Because diminished false beliefs cannot be mistaken as veridical memories reconstructed during imagery, they are less subject to criticisms of traditional false belief studies using self-report measures.

Imagery encoding and false recognition errors: exploring boundary conditions of imagery's enhancing effects

After generating images based on descriptions of object interactions, false recognition errors can be substantially reduced in the Deese-Roediger-McDermott (DRM) task. Boundary conditions for this effect were examined in three experiments by testing imagery encoding tasks against encoding tasks used previously to alter false recognition levels. False recognition errors were lowest following imagery encoding whether comparisons involved an object interaction encoding task used previously (Experiments 1 and 2) or a new version of the task (Experiment 2). In addition reductions in false recognition errors were observed in a new imagery-encoding task (Experiment 3). Generating descriptions had differential effects on "remember" responses to falsely recognised items (Experiment 2). In combination with content analyses on participants' descriptions, these findings speak to alternative explanations for the effects of imagery encoding on false recognition errors. The findings also have implications for the use of DRM results in developing recommendations regarding the use of guided imagery in applied contexts.

When plausibility manipulations work: an examination of their role in the development of false beliefs and memories

In the current study we examined whether prevalence information and imagery encoding influence participants' general plausibility, personal plausibility, belief, and memory ratings for suggested childhood events. Results showed decreases in general and personal plausibility ratings for low prevalence events when encoding instructions were not elaborate; however, instructions to repeatedly imagine suggested events elicited personal plausibility increases for low-prevalence events, evidence that elaborate imagery negated the effect of our prevalence manipulation. We found no evidence of imagination inflation or false memory construction. We discuss critical differences in researchers' manipulations of plausibility and imagery that may influence results of false memory studies in the literature. In future research investigators should focus on the specific nature of encoding instructions when examining the development of false memories.

Acts of generating and their sources: predicting the effects of imagery encoding on false recognition errors

In the two experiments reported here the basis of the beneficial effects of generating images on false recognition errors is investigated. Acts of generating (descriptions, images, or both) were manipulated while examining the effects of the source of descriptions guiding imagery generations (participant vs peer). False recognition errors were relatively high across encoding conditions except when imagery generations were based on participants' own descriptions (Experiments 1 and 2). These differences in the acts of generating were not attributable to differences in the cohesiveness of descriptions themselves. Acts of generating led to greater "remember" responses than "know" responses only when participants were not the source of the descriptions used to generate images (Experiment 2). Results highlight the importance of examining the effects of the source of descriptions for guiding imagery (participant or peer) when testing predictions about the effects of imagery encoding on false recognition errors.

Imagery encoding and false recognition errors: Examining the role of imagery process and imagery content on source misattributions

Imagery encoding effects on source-monitoring errors were explored using the Deese-Roediger-McDermott paradigm in two experiments. While viewing thematically related lists embedded in mixed picture/word presentations, participants were asked to generate images of objects or words (Experiment 1) or to simply name the items (Experiment 2). An encoding task intended to induce spontaneous images served as a control for the explicit imagery instruction conditions (Experiment 1). On the picture/word source-monitoring tests, participants were much more likely to report "seeing" a picture of an item presented as a word than the converse particularly when images were induced spontaneously. However, this picture misattribution error was reversed after generating images of words (Experiment 1) and was eliminated after simply labelling the items (Experiment 2). Thus source misattributions were sensitive to the processes giving rise to imagery experiences (spontaneous vs deliberate), the kinds of images generated (object vs word images), and the ways in which materials were presented (as pictures vs words).