The Deese-Roediger-McDermott (DRM) Task: A Simple Cognitive Paradigm to Investigate False Memories in the Laboratory

Summary

Here we present the Deese, Roediger and McDermott (DRM) task, a tool to study false memories in the laboratory. Subjects study lists of semantically related words (e.g., nurse, sick, etc.), and later falsely remember an unstudied word (doctor) that represents the gist, or theme, of the word list.

Abstract

The Deese, Roediger and McDermott (DRM) task is a false memory paradigm in which subjects are presented with lists of semantically related words (e.g., nurse, hospital, etc.) at encoding. After a delay, subjects are asked to recall or recognize these words. In the recognition memory version of the task, subjects are asked whether they remember previously presented words, as well as related (but never presented) critical lure words ('doctor'). Typically, the critical word is recognized with high probability and confidence. This false memory effect has been robustly demonstrated across short (e.g., immediate, 20 min) and long (e.g., 1, 7, 60 d) delays between encoding and memory testing. A strength of using this task to study false memory is its simplicity and short duration. If encoding and retrieval components of the task occur in the same session, the entire task can take as little as 2 - 30 min. However, although the DRM task is widely considered a 'false memory' paradigm, some researchers consider DRM illusions to be based on the activation of semantic memory networks in the brain, and argue that such semantic gist-based false memory errors may actually be useful in some scenarios (e.g., remembering the forest for the trees; remembering that a word list was about "doctors", even though the actual word "doctor" was never presented for study). Remembering the gist of experience (instead of or along with individual details) is arguably an adaptive process and this task has provided a great deal of knowledge about the constructive, adaptive nature of memory. Therefore, researchers should use caution when discussing the overall reach and implications of their experiments when using this task to study 'false memory', as DRM memory errors may not adequately reflect false memories in the real world, such as false memory in eyewitness testimony, or false memories of sexual abuse.

Introduction

The Deese, Roediger and McDermott (DRM) task was initially created by Deese¹, and later revitalized by Roediger and McDermott² as a convenient means of studying false memory in the laboratory. Although some^3,4 argue it should be called the DRMRS task, for the contributions of Read⁵ and Solso⁶, the most common name in the literature is the DRM task, and we call it by that name here. After a seminal paper published by Roediger and McDermott², interest of false memory research skyrocketed (see⁷), resulting in over 2,800 citations of that article to date. According to Roediger and McDermott, they revived the experimental design created by Deese because there was no reliable laboratory paradigm to induce false recall, while evidence of false recognition (e.g.,^8,9) did "little to discourage the belief that more natural, coherent materials are needed to demonstrate powerful false memory effects"².

One such example of a "more natural" paradigm is the misinformation paradigm^10,11. In this task, subjects are presented with a story through pictures, slides, or video. Later, misleading information is provided, and the question is whether subjects will incorporate this misleading information into their recollection of the story. The DRM task is simpler than the misinformation paradigm in several respects. DRM encoding requires only the quick presentation and learning of lists of words, either visually or aurally. Retrieval testing for the DRM task is equally convenient regardless of the particular method used. In a recognition test participants are presented with a subset of the encoded words, the critical lure words (e.g., 'doctor'), and unrelated lure words and have to make simple judgments of whether they remember each word or not, whereas in a recall test, participants have to write down all the words they are able to remember. In contrast, free recall testing for the misinformation paradigm is impractical, as it requires time-consuming content analysis. Additionally, the DRM task does not require any manipulation between encoding and testing, as DRM 'false memories' are spontaneously self-generated. The misinformation errors, on the other hand, are induced via external suggestions. Although both the DRM and misinformation paradigms are argued to assess false memory, newer studies have found small (r = 0.12)¹² or no relationship^13,14 between the misinformation and the DRM effects, suggesting that different mechanisms may be at play for each type of false memory. Moreover, the DRM illusions are argued to be a byproduct of the constructive nature of memory¹⁵, which can be considered an evolutionarily adaptive process¹⁶.

The DRM false memory effect is highly robust across studies (for quantitative reviews see ^17,18), and there is considerable evidence that the DRM task is quite reliable¹⁹ (but see²⁰). The DRM false memory effect has been found using various delay intervals, including those as short as an immediate test, and those delaying memory testing until 60 days later^21,22,23 (but see ²⁴). Warning subjects of the DRM illusion reduces, but does not erase, the effect ^14,25. The DRM effect has also been found with different encoding strategies, such as changes in word presentation duration²⁶, and can be increased by several post-encoding manipulations, such as sleep²⁷ or stress²⁸.

Moreover, the DRM task has been utilized by many laboratories to study false memory formation in a variety of subject populations, such as children^29,30,31,32 and older adults³³, and in a variety of research fields, including individual cognitive (e.g., working memory^20,34) and personality differences³⁵, neuroimaging^36,37, and neuropsychology³⁸. In spite of its popularity, however, many have argued against the generalizability of the DRM task, and whether the creation of DRM false memories is comparable to the naturalistic creation of false autobiographical memories outside of the laboratory, such as memories of child abuse recovered in psychotherapy^39,40,41. Nonetheless, several studies have found that subjects that are more susceptible to DRM false memories are also more prone to autobiographical memory distortions⁴², fantastic autobiographical memories (alien abductions⁴³; past lives⁴⁴), and recovered autobiographical memories⁴⁵.

In short, the DRM task has been a useful tool to investigate the neurocognitive underpinnings of the (re)constructive nature of memory^15,16, regardless of the ongoing debate about how appropriate and relevant it is in the study of autobiographical false memories⁷. In the current report, the DRM task procedures are explained in their simplest form, with a focus on targeting memory consolidation processes (i.e. experimental manipulations, such as sleep and stress, occur after encoding has finished and are thus used as tools to evaluate consolidation), as this has been the focus in our laboratory. The authors refer the reader to Gallo (2013)⁴⁶ for an excellent review of the DRM task, along with the different variations on encoding and testing procedures.

Protocol

The Institutional Review Board of the University of Notre Dame approved all of the procedures, including use of human subjects, discussed here. The preparation and the administration of the DRM task materials described below were used in a published study²⁸, in which the effects of psychosocial stress following DRM word list encoding were assessed 24 h later.

1. Preparation of DRM Task

1. Use the word lists from Stadler, Roediger, and McDermott⁴⁷, presented in the Appendix, to select the appropriate number of word lists for the experiment. From Tables 1 and 2, select the word lists with the highest probability of false recall and recognition. The more word lists used in the experiment, the greater the number of false words participants will have a chance to remember.
   NOTE: Tables 1 and 2 show the probability of false free recall and recognition memory, respectively, of the top 18 word lists used by Stadler et al.⁴⁷. The Appendix presents the complete word lists. See also Gallo and Roediger⁴⁸ for additional normed word lists.
2. Prepare the encoding task
   1. Choose modality of presentation of word lists. See Discussion for issues regarding the selection of presentation modality.
      NOTE: Presentation modality can be either visual or auditory.
   2. If auditory presentation is chosen, digitally record all the words in each list. Use professional-grade equipment (e.g., Rode NT1-A microphone), preferably an unfamiliar voice and a soundproof or sound-resistant room.
   3. Record the word lists in descending strength of association, as they are presented in the Appendix, at a rate of one word every two seconds.
   4. At the end of each list, include a reasonably long delay (e.g., 12 s) of silence, followed by a 1 s tone, 2 s of silence and then the start of the next list. This helps participants parse the individual lists.
   5. Use a audio-editing software (e.g., Audacity) to apply these standards.
      1. Drag and drop the audio file into the audio-editing software.
      2. Use the mouse cursor to select the portion of audio to which silence will be applied.
      3. On the top, select Edit>Remove Audio>Silence Audio.
      4. To apply the 1-s tone at the start of each list, use the copy and paste options in the audio-editing software.
      5. To save the recording, press STOP, select File>Export, and choose file format and destination of the audio file.
3. Prepare the testing task
   1. Choose a retention interval between encoding and testing that is appropriate for the experiment. If addressing the effects of stress on memory performance, choose at least 24 h.
   2. For the free recall task, have a blank piece of paper or a blank document in a word-processing application (e.g., MS Word) ready.
   3. For the recognition task, select words to include in recognition task.
      1. Include study words (i.e. words presented at encoding) from positions 1, 8, and 10 from each list included in the encoding task². See Appendix for complete word lists.
      2. Include all critical lure words (i.e. false words not presented at encoding that represent the gist of the word list) from each list included in the encoding task. See Appendix for complete word lists and their appropriate critical lure.
      3. Include the same number of additional, non-presented words (i.e. foil words that are unrelated to any of the studied DRM lists), from other, non-studied DRM word lists, from the same positions (1, 8, and 10) and their corresponding critical lures.
         NOTE: For example, if 15 DRM word lists are presented during encoding, for the recognition test, present 120 words: 45 study words, 15 critical lure words, 45 nonpresented list items from other non-studied DRM word lists, and 15 critical words from those nonstudied DRM word lists.
   4. Use experiment creation software (e.g., E-Prime) to create self-paced presentation of the words and to achieve data collection.
      1. Use black font with a white background, and reasonable font size, depending on screen size/resolution.
      2. In a standard old/new recognition test, use separate keys to assign responses; such as the 'Z' key for old and the 'M' key for new. If possible, add this legend in with the presentation of each word on the screen. Software such as E-Prime will automatically collect reaction times and key responses.

2. Administration of DRM Task

1. Administration of encoding task
   1. Ask subject to sit in front of device containing the recording of the word lists. Ensure subject is comfortable.
   2. Read the following instructions to the subjects: "For this cognitive task you will be listening to lists of words. At the final word of each list, there will be a 12 s break, followed by a 1 s tone, followed by 2 s of silence, and then the start of the next list. Please pay close attention to the words because you will be tested on them at the next session."
   3. Ask subject to put on headphones. To ensure participants have no distractions, turn off the computer monitor. Press play.
   4. Inform participant that this session has ended and provide them with instructions for the next (testing) session.
2. Administration of testing task
   1. Free recall test
      1. Ask subject to sit down in front of a table or desk (if using pen and paper) or in front of the computer (if using a word processing blank document).
      2. Read the following instructions to the subject: "This part of the task involves a simple memory test. Please write down all the words you can remember from the lists you heard in the last session. You have 10 min to recall all the words you can. When there are 2 min left, I will let you know. Any questions?"
      3. Answer any questions the subject may have.
      4. Start the timer and inform subject of the two-minute warning mark.
      5. Stop subject after time is up.
   2. Recognition test in the computer
      1. Open recognition test with the experiment creation software.
      2. Ask subject to sit in front of computer.
      3. Read the following instructions to the subject: "This is a simple recognition task. You will see a word on the screen. Use the keyboard to answer whether each word is old (that is, on one of the lists you heard/saw previously) or new. You will use the 'Z' key if you think the word is old and the 'M' key if you think the word is new. This is self-paced, but we are also measuring your reaction time, so answer as quickly but accurately as you can. Let me know you are done. Any questions? ".
      4. Answer any questions the subject may have.
      5. Start the recognition test and wait for the subject to finish.
   3. Debrief the subject and thank them for their participation in the study.

Results

Using the procedure presented here, the authors have been able to reliably produce the DRM effect in two independent experiments; that is, subjects recall and recognize, with high probability, non-presented critical words that can be considered false memories for the 'gist' of the word lists.

Results for experiment 1 (see Figures 1 and 2) have been published elsewhere²⁸. ...

Discussion

In this report, the authors described a highly used cognitive task that reliably produces gist-based false memories in human subjects. It is important to note that, in the current report, the DRM task was presented in one of its simplest forms, very similar to the original protocol used by Deese¹ and Roediger and McDermott². The similarity with the original protocol used in the experiments described here has one particular exception: a long delay (24, 48 h) between encoding...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Computer			No particular brand/type required.
Headphones			No particular brand/type required.
RODE NT1-A 1" cardioid condenser microphone	Rode	http://www.rode.com/microphones/nt1-a	recording equipment used to record the wordlists
Audacity	Audacity	http://www.audacityteam.org/	for editing the recording of the wordlists
E-Prime	Psychology Software Tools, Inc.	https://www.pstnet.com/eprime.cfm	for stimuli presentation and/or testing
MS PowerPoint (optional)	Microsoft		for stimuli presentation and/or testing
MS Word (optional)	Microsoft		for free recall testing. Any word processor application will work.