The method presented here induced false memories using lists of related words and also assessed the effects of imagery instructions on the recall and recognition of those false memories. This protocol details a modified version of the Deese Roediger McDermott (DRM) paradigm.
Associated word list procedures can elicit false memories in predictable ways by inducing associative processing, thus making it harder to monitor the accuracy of memories. The purpose of the method presented here was to induce false memories using lists of either semantically or phonologically related words and to assess the effects of imagery instructions on the recall and recognition of those false memories. To do this, we used a modified version of the Deese Roediger McDermott (DRM) paradigm. We adapted word lists from previous DRM studies to suit imagery procedures and created an automated presentation to present the word lists in classroom settings. We then recruited undergraduate classes and instructed some of the classes to create mental images of the list words as they were being presented, while instructing the other classes to simply remember the words. The automated presentation presented word lists to participants, one word at a time, alternating between phonologically and semantically related lists. Participants used paper-pencil recall packets to immediately recall list items, complete a distractor activity, and take a subsequent final recognition test. Often, participants immediately recalled and later recognized words that were related to the list items but were not actually presented; these are known as critical lures and indicate a false memory. The protocol detailed here describes a four-step procedure – list presentation, immediate recall, distractor phase, and final recognition – that can assess the effects of list type and imagery instruction within the DRM paradigm on memory. The automated nature of the list presentation provides the ability to systematically vary variables of interest, and the paper and pencil method of data collection affords an easily accessible method for collecting data in classroom settings. The protocol also offers options to modify the procedure to a more traditional DRM paradigm without imagery and/or list type manipulations. The use of this protocol can provide results relevant to both classroom learning and cognitive science principles.
Memory is malleable and fallible, and these days people realize the limitations of their own memory system. But how do memory errors arise? What mechanisms are responsible for errors in memory retrieval? We modified a widely used and highly cited laboratory-based procedure called the Deese Roediger McDermott paradigm (DRM)1,2 to investigate the influence of different variables on memory errors. In traditional DRM procedures, participants are asked to learn lists of semantically related words (e.g., table, couch, desk, lamp, pillow, stool, bench, rocker). When later asked to recall and/or recognize the words from the lists, participants often report seeing words that were semantically related to the lists but not actually studied (e.g., chair). False memories for these words, referred to as critical lures, can occur 55% – 80% of the time in standard procedures2,3.
The Activation Monitoring Framework is often cited as a theoretical basis for memory errors that arise from the DRM paradigm. Specifically, DRM false memories are attributed to the dual processes of activation (i.e., the tendency for pieces of information currently active in working memory to "spread" and also activate other, related pieces of information) and monitoring (i.e., assessing the accuracy and/or source of something being remembered)5,6. The process of studying semantically related DRM lists causes activation to spread from the list words to the critical lure and thus activates the critical lure in working memory. The result is a false memory that may not be accurately monitored during later tasks.
The three-phase testing procedure inherent to the DRM paradigm allows cognitive psychologists to manipulate a number of variables during the process of encoding (study of the list items), retention (storage of the list items while completing a distractor task to disrupt working memory), or retrieval (a memory test), to better understand the specific processes that contribute to memory errors. Our procedure expands use of traditional DRM procedures to directly compare memory error rates for different types of content during encoding (e.g., semantically related versus phonologically related)9, test type during retrieval (e.g., a recall task versus a recognition task)10 and, perhaps most notably, imagery encoding processes during list study11,12,13,14.
Our primary interest in developing this protocol was to better understand possible effects of imagery on recall and recognition, particularly whether the effects of creating mental images of the list words during encoding (e.g., imagining them) would vary according to whether the list words were related to the critical lure according to sound (i.e., phonologically) or meaning (i.e., semantically). For instance, for the phonological list log, hog, dock, bog, fog, doll, frog, jog, and dot, the critical lure is dog. For the semantic list mug, saucer, tea, coaster, lid, coffee, straw, and soup, the critical lure is cup. We were interested in whether imaging the list words affected the associative processing for those lists differently. While traditional DRM word lists contain 12-15 semantically related list words2, our procedure employed 8-item word lists. These lists were modified from 16-item lists previously developed to investigate the converging effects of phonological and semantic word associations on false memories9. In order to adapt typical DRM procedures to include imagery instructions, we shortened the word lists by selecting the 8 words from each list that were easiest to create mental images of. This allowed for the elimination of less concrete words (e.g., pun, worst) that were hard to imagine. Additionally, we modified a computer-based word list presentation utilized in previous research15 to standardize the presentation of materials and also developed paper/pencil recall and recognition measures to more appropriately suit classroom environments.
Our results did not suggest an interaction between list association type and imagery procedures, but they did demonstrate the significant main effects of imagery and list type14. We pursued this line of inquiry because of the robust literature of imagination inflation effects suggesting enhanced feelings of belief and memory in past childhood events that are repeatedly imagined16,17,18. However, recently researchers suggest that perhaps not all imagery is created equal and that the nature of imagery instructions mediates the effects on false memory rates19. One possible limitation to the work assessing imagination inflation effects is inherent in the procedure itself. That is, participants are asked to provide Likert scale ratings of their confidence or belief in experiencing certain events in childhood, and following imagination of those events, ratings are provided a second time to assess changes (specifically increases) in those ratings. One possible problem with this procedure is a lack of control over the veracity of experiences that participants must identify with confidence ratings both prior to and after the imagery phase. In some studies, researchers consult family members for corroboration20; however, a majority of the research examining imagination inflation relies solely on the word of the participant.
DRM procedures offer methodological advantages over other memory paradigms, including imagination inflation procedures, because researchers maintain control over the content being activated in working memory through the design of the lists. Specifically, researchers select the list items according to their associative strength to the critical lure and can easily measure when a participant commits the targeted memory error (e.g., chair was not on the studied list but was recalled at test). This content control provides insight into processes that drive associative memory errors, affording researchers the opportunity to explore other potentially important factors driving false memory errors, such as the construction of visual images during list encoding21 or even elaborating on the list items to generate complex event narratives11.
This protocol employs a presentation administration of materials and a paper and pencil format of data collection that allows researchers to collect participant data in large groups (e.g., classrooms), while systematically varying variables. The accessibility and experimental control offered by this protocol provides an opportunity to teach students about memory processes with an in-class demonstration while reliably collecting data. Compared to laboratory-based DRM procedures, this context makes results more applicable to classroom learning, thus informing both cognitive science and educational psychology. In addition, this protocol provides optional modifications that can be utilized to remove the usage of imagery instructions or varying list types, thereby offering a construction-kit type approach that allows for more personalized use.
All methods described here have been approved by the Institutional Review Board of Georgia State University.
1. Material Preparation
2. Recruitment
3. Optional Modifications to Protocol
4. Procedure
Effects of DRM Procedures on False Memories: Standard DRM Instructions without Imagery
To illustrate standard DRM procedures' ability to induce false memories, we analyzed rates of falsely remembering non-list words during recall and recognition. Table 1 reports proportions for the different types of false remembering that occurred during recall and recognition. During immediate recall, participants recalled unpresented words on 20% of the lists, suggesting the protocol induced spreading activation to unpresented words that were then immediately remembered as being seen on 1 out of every 5 lists. Of those false recalls, 13% were recalls of the critical lures and 8% were recalls of other non-list words, which we refer to as non-critical lures. A repeated measures analyses comparing the proportion of lists in which the critical lure was recalled and the proportion of lists in which a non-critical lure was recalled indicated that participants recalled critical lures at significantly higher rates than non-critical lures, F(1, 48) = 9.24, p = .004. While this finding suggests that the DRM protocol successfully converged on and activated the critical lures more so than other words, it was not to the degree that longer DRM lists typically do. For instance, the longer 15-item lists described in protocol modification 3.2 can induce recall of the critical lure up to 55% of the time2.
To measure the effects of DRM procedures on the recognition of critical lures during the final recognition test, we compared the proportion of critical lures remembered (number of "yes" recognitions/10) to the proportion of non-critical lures remembered, which included filler list words used as distractors and their critical lures (number of "yes" recognitions/40). Repeated measures comparisons of these proportions indicated that critical lures were recognized at significantly higher rates than non-critical lures, F (1, 48) = 149.52, p < .001. Critical lures were recognized 45% of the time, whereas distractor words were only recognized 6% of the time, illustrating that the protocol induced high rates of false critical lure recognition.
When directly comparing rates of false memories across recall and recognition, a repeated measures analysis indicated that significantly higher proportions of critical lures were remembered during the recognition test (45%) than during immediate recall (13%), F (1, 48) = 145.14, p < .001. This finding is typical and demonstrates the different demands that each task places on memory and also illustrates the ability of this protocol, which utilized both types of memory tasks, to capture instances of false memory that were present during one task but not the other. The final recognition task measured instances of false memory that were absent during free recall.
To compare the effects of using phonologically-related versus semantically-related DRM lists on false memories, we calculated separate proportions of critical lure recall and critical lure recognition for each list type (number recalled or recognized/5). See Table 1 for proportions of false memories across list types. A 2 (test type: recall vs. recognition) x 2 (list type: semantic vs. phonological) mixed ANOVA indicated that critical lures for phonological lists were recalled at higher rates than critical lures for semantic lists (rates of 14% and 6%, respectively); whereas critical lures for semantic lists were later recognized at higher rates than critical lures for phonological lists (rates of 48% and 28%, respectively). This was evidenced by a significant interaction between list type and test type for false memories, F(1, 100) = 55.36, p < .001. This finding demonstrates that the type of association between the list words affects the type and/or level of processing induced during study (i.e., differences in recall performance) and later remembering (i.e., differences in recognition performance). Semantic lists induce deeper processing of the list association and critical lure, which makes reactivation of that critical lure particularly difficult to monitor during recognition; whereas phonological lists induce shallow associative processing that is confusing and hard to monitor during recall but that largely decays by the final recognition test.
Effects of Imagery Instructions during DRM Procedures
To demonstrate the effects of modified DRM procedures that instruct participants to create mental images of the list words, we compared hit rates (e.g., correctly recalling a list word) and false memory rates across participants in imagery and non-imagery conditions. We calculated separate proportions for recall and recognition hit rates by dividing the total number of list words correctly recalled by 10 and the total number of "yes" responses to list words on the recognition test by 30. A 2 (imagery vs. non-imagery) x 2 (proportion of recall hits vs. proportion of recognition hits) mixed ANOVA indicated a significant main effect for imagery instructions. Participants in the imagery condition remembered more list words than participants in the non-imagery condition during both recall (64% vs. 60%) and recognition (93% vs. 88%), F(1, 100) = 5.90, p = .02. A similar 2 (imagery vs. non-imagery) x 2 (proportion of critical lures recalled vs. proportion of critical lures recognized) mixed ANOVA on false memory rates indicated another main effect for imagery instructions, F(1, 100) = 3.82, p = .05. Participants who imagined the list words remembered fewer critical lures than participants receiving standard DRM procedures during both recall (7% vs. 13%) and recognition (39% vs. 45%).
A larger mixed model with list type added in as an additional repeated measure factor did not indicate any significant interaction between list type and imagery; imagery affected memory for both list types similarly. However, it is important to note that when list type was added to the mixed model, the impact of imagery on false recognition was only marginally significant, F(1,100) = 3.46, p = .066. Previous work has also indicated null effects of imagery during false memory recognition10, suggesting that simple imagery instructions (i.e., create a mental image in your head) are not sufficient aid during monitoring when the critical lure is reactivated during recognition. The relative decreases in false recall and increases in list word recall and recognition reported here are in line with previous work employing imagery instructions in DRM procedures10,23. Further, the effects of imagery would likely be more pronounced if protocol modification 3.2 was implemented, which utilizes longer semantically-related lists10.
Table 1: Proportions of the Different Types of Words Falsely Remembered Following Standard Instructions. This table illustrates the proportions of the various types of words falsely remembered by the non-imagery group. Rates of false memories for critical lures and non-critical lures are illustrated across test type and list type.
Figure 1: Comparisons of Imagery and Non-Imagery. This figure illustrates the proportions of list words accurately remembered and the proportions of critical lures falsely remembered during recall and recognition across imagery and non-imagery conditions. Error bars represent the standard errors. Please click here to view a larger version of this figure.
The protocol employed in this study modified a widely used word list procedure, the Deese Roediger McDermott (DRM) paradigm, to assess the effects of associative processing with and without imagery instructions on false memories in a classroom-based procedure. The expansion to include the variables of list association type, test type, and imagery instruction implemented here afforded the ability to analyze how each of these complex factors influenced a learning context independently, as well as how they interacted, providing insight into memory processing strategies. This protocol also offers optional modifications that can be used if a more traditional DRM procedure is desired, wherein imagery instructions or different list types are employed. These modifications can be implemented by only using the non-imagery condition with shortened presentation durations and/or substituting longer semantically-related word lists.
The automated presentation of DRM materials described in this protocol affords absolute control of presentation duration, which is an essential element to control considering that the length of presentation duration impacts recall across phonological and semantic lists differently22. A relatively long 5-second presentation duration was employed here to allow time for participants to engage in imagery procedures. However, the presentation can be easily modified (see protocol 3.1) to utilize shorter presentation durations when imagery is not being used. Shorter durations are associated with increased false memory rates for both phonological and semantic lists22. This automated format also allows for systematic control of list order presentation, which is necessary for counterbalancing the presentation of both list types. The false memory rates for phonological and semantic lists reported here suggests that the protocol's alternating presentation of list types successfully induced the associative processing inherent to each list type, and the significant interaction between list type and test type reported here demonstrates that phonological and semantic associative processing apply different constraints on memory.
The simple imagery instructions employed here were sufficient to significantly increase memory for list words and decrease false memory recall, but were not sufficient to decrease false recognition after a distractor activity. Using imagery instructions in this context not only provides insight into the mechanisms responsible for associative processing and source monitoring during classroom learning, but also has the ability to demonstrate the usefulness of creating visual memory cues to students.
The word lists included in this protocol were modified from previously normed word lists9 to only include concrete words that participants could mentally represent with visual imagery. Less concrete words (e.g., worst, dug, pun, accident, etc.) were removed from 16-item lists, resulting in shorter 8-item lists. While our shorter lists frequently created false memories in participants during recall, they did not converge onto one specific critical lure to the extent that longer lists typically do; they activated other related words that were misremembered in addition to the critical lures. This illustrates the function of list length on the convergence of associative processing onto one critical lure. Thus, false memories may be underestimated during recall when using shorter lists if other related non-list words are not taken into account. If phonological processing is not of interest, the 3.2 protocol modification can be utilized to increase false memory rates using longer semantically-related lists.
This protocol utilizes immediate recall and final recognition tests. When both of these assessments are used in conjunction and separated by a delay (i.e., the 7-minute word search), instances of false memory that may not be captured by one task can be captured by the other. For instance, our immediate recall task captured phonological false memories that had decayed by final recognition, and our final recognition task captured semantic false memories that were successfully monitored, or possibly not activated, during immediate recall. The combined use of both tasks provides a more comprehensive examination of the mechanisms responsible for false memories, namely activation and monitoring. Depending on the variables of interest, this protocol can be easily adapted beyond the specific modifications provided here by varying presentation versions by a single variable and comparing recall and recognition performance across versions. It is our hope that this adaptability and construction-kit approach offered here proves particularly useful for research and classroom usage.
The authors have nothing to disclose.
We send special thanks Dr. Mary Ann Foley and Dr. Karen Zabrucky for collaborative work on research projects informing our methodology in this paper.