Investigating the Effects of Divided Attention on Memory Source Monitoring using the DRM Task

Investigating the effects of divided attention on memory source monitoring using the DRM taskAbstract

False memories can exist due to a variety of psychological factors, and have been the subject of scientific investigation for a long time. Researchers have always been interested in discovering the reason why the brain tends to make false memories. Mounting evidence toward the role of attention systems in this mechanism. While some research shows the effect of divided attention on both memory encoding and retrieval, neuroimaging data has failed demonstrate the former. To address these conflicted findings, we used the Deese-Roediger-McDermott (DRM) false memory paradigm under full attention or divided attention by the concurrent administration of the random number generation (RNG) task. 78 undergraduate psychology students, age 18 – 27, took part in this experiment. This shows that dividing the attention will significantly increase the number of falsely remembered words but will not have a significant effect on the correctly remembered words, implying that the stronger effect of divided attention on memory retrieval. This possibly is due to the active role of attention in monitoring and retrieving the memories.

Keywords:  False Memory, DRM, Divided Attention, Memory Encoding, Memory Retrieval

Investigating the effects of divided attention on memory source monitoring using the DRM task

The human capability to encode and retrieve explicit memories in short- and long-term, has indubitably contributed to our evolutionary rise to the top of the food chain through the millennia (Nakamaru, 2016; Smid & Vet, 2016). It has been demonstrated that the human ability for remembering long sequences exceeds those of most other members of the Animalia kingdom (Ghirlanda, Lind, & Enquist, 2017). Although, we make frequent mistakes by remembering wrong facts or stimuli. The best demonstration of this fact is through the behavioural paradigm first designed in the 1950s (Deese, 1959) and then fully developed by in the 1990s (Pardilla-Delgado & Payne, 2017; Roediger & McDermott, 1995), called the Deese-Roediger-McDermott (DRM) paradigm. The subjects in this paradigm read a sequence of words, each set of which is designed around a non-presented ‘lure word’. The lure words are the semantic concept related to all the words in the set. For instance, the sequence “bed, sheet, comfort, snore, yawn” revolves around the lure word “sleep”. Roedriger & McDermott also published their word sets used for the 1995 paper (Roediger & McDermott, 1995), which has let researchers reuse them for designing experiments investigating false memory recall.

Both memory encoding and retrieval mechanisms have been suggested to play out in false memory recall (Abe et al., 2013). Other mechanisms relating to encoding and retrieval have also been implicated in the false memory recall. It has been demonstrated that the emotional content of the encoded memories can increase the number of false memories recalled (Bookbinder & Brainerd, 2016; Mirandola, Toffalini, Ciriello, & Cornoldi, 2017; Storbeck & Clore, 2011). In the recent years, mounting evidence has been pointing out that attention plays an important role in false memory recall (Shah & Knott, 2018). Patients with ADHD have been observed to have higher false memory rates and higher knowledge corruption rates in the DRM task (Soliman & Elfar, 2017). Hence further studies are necessary to understand the mechanisms of attention in false memory recall. To address this gap, we used the DRM word remembering task in full and divided attention states and compared the performances. In this experiment, we used the random number generation task for achieving the division of attention, as it can put a high pressure on encoding and retrieval processes of the working memory (Baddeley, Emslie, Kolodny, & Duncan, 1998; Knott & Dewhurst, 2007).

In the current literature, two possible mechanisms have been suggested for false memory recall. We present each of these possibilities and their implications for this research:

Explanation #1: Encoding at fault

An argument has been made that the false memory recall is an effect of wrong encoding of memory material. This would mean that an erroneous engram of the memory has been stored in the brain upon encoding which is then retrieved during the recall task.

Explanation #2: Retrieval both at fault

Another possibility is that false memories are a result of an error in the memory recall system. This is supported by biological evidence such as Ramirez et al. (2013) and Liu, Ramirez, & Tonegawa (2014), demonstrating that by stimulating a region in the Dentate Gyrus of the hippocampus during memory retrieval, false memories can be induced. Loftus has also demonstrated that the false memories do not have the signature true memory reactivation of primary sensory areas (Stark, Okado, & Loftus, 2010). This is also in line with Barense’s work showing possible false memory induction after reactivating the memory trace by presenting parts of the encoded stimulus (Sinclair & Barense, 2018).

As an example, when a student tries to recall what the instructor has mentioned in the classroom, they possibly try first to remember the words being said. If this fails, they would try to recall the notes they have taken of the class, and reconstruct the missing auditory information using visual memory of the written material. In this process, a piece of information might be marked with an incorrect gain function (scored closer to the stimulus than it truthfully is) by mistake or by association with similar semantic subjects, it can be falsely added to the memory trace, producing the signature false positive. In the context of the DRM paradigm, we can explain that the individual unconsciously tried to explain the data using available information, but fell to mistakes and falsely attributed the memory as old (previously observed) due to the semantic context of the lure words.

Based on the current knowledge, we expect to see a higher false-memory recall in subjects with divided attention as

Methods

Participants

This experiment was undertaken with the informed consent of the undergraduate students in a second-year psychology class. Seventy-eight participants (50 females, 19 males, 8 other or unspecified) aged 18 to 27 (M=20.55, SD=2.08) took part in the experiment. The participants were divided into the divided attention (DA) and full attention (FA) groups based on the location of seating; students on the right half of the classroom were assigned to the FA group and the students on the left side were assigned to the DA group.

Materials & Stimuli

The experiment used a sequence of words from Knott & Dewhurst (2007), which is itself adopted from Stadler, Roediger, & McDermott (1999). Both the groups were concurrently given a sequence of words. The word sequence consisted of 4 sets of 10 words presented loudly by the instructor with the pace of 1 word per 2 seconds. Each set of words included 2 lure words not presented with the sequences. The FA group was instructed to simply listen to the presented sequences, whereas the DA group was instructed to write down a random number from 1 to 20, in synchrony with the presentations of each word (i.e. every 2 seconds). All participants were then tested for correct and false memory recall. Participants from both the groups were instructed to answer yes/no whether they had seen a 48 test words in the presented sequence, using the TopHat portal (TopHat Inc., Toronto, ON, CA) on their digital devices. These test words included 8 of the presented words (2 from each trial, across 4 trials) plus all the 8 lure words (2 per trial, across 4 trials) plus 32 unrelated non-presented non-lure words, dispersed randomly to prevent stereotyped interactions between their memory traces.

Results & Statistical Analysis

The participants indicated whether or not the test word was in the sequence. Their responses were analyzed using SPSS (IBM Corp., Armonk, NY, USA). The first independent-samples t-test concluded that the mean of correctly-remembered words in the FA group (M=6.11, SD=1.37) and that of the DA group (M=5.52, SD=1.61) had no significant difference, t(76) = 1.719; p ≈ 0.09. But the mean for FA was higher than the DA. No definite answer can be drawn, but a non-significant decrease in true positives was seen as a result of dividing the attention.

Another key observation was made by running an independent-samples t-test on the false memory rates. It concluded that the mean false memory recall rate for the DA group (M=5.1, SD=1.32) was significantly different than that of the FA group (M=4.06, SD=1.71) and higher. In other words, the divided attention group showed a significantly higher rate of false positives.

Discussion

We demonstrated that dividing the attention using the random number generation task significantly increases false positives more strongly and more significantly than it lowers true positives. Two possible explanations were presented in the introduction (Cf. pg. 4)

This experiment’s findings stand against this theory that. This theory implicates that the errors in encoding are in charge of false memories. In that case, the decrease would appear with the same rate in both the DA and FA groups, as it has been shown that DA affects memory encoding much more strongly than it affects recall (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996, p. 199).

Explanation #2

Seeing the present experiment with this light concludes that dividing the attention causes a mild decrease in the correct recall, as it would do in any categorized or free recall task. But the strong decrease shown in the false memory recall is due to the exclusive effects of attention on the false memory recall.

Next lines of research can explore the reason behind this effect. It can be hypothesized that the brain monitors the memories that are to be retrieved and in the case of a missing piece of information, it uses attentional resources for reconstructing the picture using other available data, modifying the memory during the retrieval plasticity window. Frankly, more experiments are needed to precisely affirm the nature of this relation between the units.

In short, we demonstrated that divided attention affects false memory retrieval more strongly than it affects correct memory retrieval

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