Excerpt
Abstract
This study sought to find out whether the effect of positive mood on familiarity also transfers to déjà vu. It was hypothesized that people with a higher positive affect will be more likely to commit errors in a memory judgment task, and subsequently experience more déjà vus in a lab study. 42 participants of both sexes with a mean age of 23 participated for course credit or voluntarily. We used a 2 x 2 experimental research design with a mood induction (positive and neutral) and a computer task with pictorial stimuli; assignment to the mood conditions was random. The dependent variables were performance at a memory test and déjà vu occurrence. Independent variables were level of positive affect and processing style (deep or shallow). While we did not find that people with a higher positive affect were less accurate in the memory test, we found that more positive people were more likely to experience déjà vu. We concluded that the results of the present study could shed new light on previous studies but urge their replication with a larger sample size.
The impact of Affect on Déjà vu:
Does Happiness provoke Déjà vu?
Déjà vu, that particular funny feeling that we get when we think that we have seen or experienced something before despite disconfirmatory evidence, is familiar to most of us. Descriptive studies have shown that approximately two thirds of all people have experienced at least one déjà vu in their life (Brown, 2003).
One of the pioneering researchers in the field of déjà vu was Gerard Heymans, a Dutch scholar who lived more than a hundred years ago. In his studies from 1904 and 1906 he collected survey data about possible predisposing factors such as personality traits. Some of his conclusions were later confirmed using advanced statistical methods (Sno & Draaisma, 1993), including the hypothesis that a “reduction of psychological energy” caused by an episode of mental or physical effort coincides with déjà vu occurrence. Since then, many more studies sought to investigate this fascinating phenomenon. In a meta-analysis déjà vu was found to be most frequent in young adults, and declines with age. Educated, liberal and well-traveled individuals appeared to experience déjà vu more often (Brown, 2003).
Inspired by this research we designed a longitudinal descriptive study ourselves (unpublished raw data). We asked first year students bimonthly to report their déjà vu experiences along with related data. In the beginning we recorded demographics, factors that we had reason to believe could be related, as well as a measure of the Cognitive Failures Questionnaire (CFQ; Broadbent, Cooper, FitzGerald, & Parkes, 1982) and a stable Positive Affect Negative Affect Scale (PANAS; Watson, Clark, & Tellegen, 1988). Students were then asked to fill in one report every two weeks either about a déjà vu they might have had or if not applicable, a cognitive failure such as daydreaming. We chose a cognitive failure as a control measure because they are very common and it is highly likely that people will experience at least one during that period. For all reports we asked for further details such as when and where it happened, how they felt (using a stable PANAS), and other surrounding circumstances, e.g. where they alone or with friends or stranger. We also asked for a detailed description of the experience itself. The study ran for a total of six months, and we collected a total of 897 reports from 147 students. Dropout was very high after the 8th; so that in analyses we used only reports from the 1st to the 8th report with the caveat that one participant must have filled in at least 3 reports. This resulted in 814 reports, of which 23% were déjà vu experiences by a total of 139 participants. This data replicated some of the findings mentioned by Brown (2003), e.g. a very high déjà vu occurrence for young adults, namely a lifetime incidence of 96.6% in our sample. While this number may seem very high, this sample confirmed to the criteria for a population with the highest déjà vu incidence; young adults that are highly educated (i.e. university students) and they travel frequently (our sample consisted of international students from different countries).
A search of the literature on déjà vu does not only lead one to descriptive studies but also to experiments in which déjà vu was successfully induced in participants. Brown and Marsh (2010) summarized the most prevailing explanations along with research findings. There are three groups of theories that seek to explain déjà vu occurrence in healthy people, as opposed to people with epilepsy for instance, who often experience déjà vu as part of their aura before a seizure. There are two cognitive explanations that will be elaborated on here. The third one that is the least relevant for this research is a physiological explanation, and suggests that déjà vu arises from an asynchronous signal transmission as an image enters the eyes and is transmitted to the occipital lobe at the back of the head for further processing.
The first group deals with perceptual theories. These theories propose that one has seen the stimulus that triggers déjà vu before, but has not processed it properly due to distraction. On second encounter the stimulus is already primed but one fails to draw the connection due to insufficient processing on the first encounter. One of the studies exploring this theory (Brown & Marsh, 2009) used symbols of low and high familiarity (for instance the “divided” symbol known from mathematics for high familiarity), along with novel symbols. Level of familiarity was determined in a pilot study by ratings of students. Participants were briefly primed with the symbols, followed by a mask, and then shown the test symbol. Primes were either identical, different or none. Participants were asked if they had seen the target symbol before, and at the end of the experiment whether they had experienced déjà vu during the session. It was found that in those trials that used an identical prime, participants reported more often that they had seen the symbol prior to the experiment. Further, 50% of the participants reported having experienced déjà vu during the session. An important caveat, however, is that the experimenters did not define déjà vu for their participants, so it may be that they reported it because they felt that they had seen it before (déjà vu means literally “already seen”) and not because of the other criteria, which are disconfirmatory evidence that this cannot be the case, and this particular feeling that accompanies such an experience.
Another proposed explanation deals with implicit memory and postulates that some feature of the déjà vu-evoking scene has been experienced before but cannot be identified. In other words déjà vu is proposed to be a source monitoring issue. And can thus be classified as a type of cognitive failure where one cannot identify the source of the memory, or does not put effort into judging it properly (i.e. instead of asking “isn’t it possible that I’ve seen this before?” one just likes to wonder about the curious nature of déjà vu). A study that capitalized on the familiarity hypothesis of déjà vu used pairs of scenes that resembled each other based on their composition but depicted distinct environments (Cleary, Ryals, & Nomi, 2009). Participants were shown study scenes that were accompanied by a name (e.g. “locker room”), and later presented a configurally similar scene (CSS), which they were prompted to identify based on the study scene. Further, they were asked to rate the familiarity of the CSS, and report whether they had experienced déjà vu or not. Results indicated an elevated likelihood of experiencing déjà vu for scenes that resembled previously seen study scenes, and a close link between experiencing familiarity and déjà vu. Again, déjà vu was not defined and participants may have been over reporting déjà vu due to demand characteristics (Cleary et al., 2009).
The familiarity hypothesis fits neatly with the observation that the given déjà vu descriptions we received in our longitudinal study do not adhere strictly to the déjà vu definition. For instance one of our participants reported the following: “ I was talking to my family and suddenly had the feeling that this situation already had happened, the same atmosphere, same persons…” While that particular feeling was reported, the situation itself is not so unique that it is impossible that some of it has happened before. People seem to identify déjà vu based on that particular feeling of familiarity, and do not question the source of it. But on closer examination one often finds that it is possible that the person committed a source error.
A novel finding we came across in our preliminary déjà vu study is that the feelings reported after a déjà vu were much more positive than those for a cognitive failure. While it is true that a cognitive failure, such as replacing ones keys is rather annoying, one may wonder why a déjà vu, which is also a type of a cognitive failure is much better liked. Further investigating the relationship between mood and déjà vu revealed that the stable PANAS score, specifically the positive affect score taken at the beginning of the study correlates with the subsequent number of déjà vus during the 6-month period. We concluded that a relationship between positive affect and déjà vu exists.
This is a promising finding in the light of existing literature about affect on memory. The affect-as-information hypothesis (Storbeck & Clore, 2004) proposes that affective information cues the encoding strategy, using either item-specific or relational processing. Item-specific encoding focuses on an item’s distinct characteristics. In contrast, relational processing works by encoding an item with regard to its related concepts. A positive mood was suggested to trigger associated concepts and keep processing at a global level and thus an item-specific style. In contrast a negative mood activates a detailed and focused processing strategy, as in the relational processing. Tested was this with two experiments using the Deese-Roediger-McDermott paradigm (Roediger, & McDermott, 1995), which uses word lists that contain related words. Participants are exposed to these and have to recognize them later using a checklist. The checklist also includes semantically related words that were not presented; known as lures. If lures were identified as previously seen, this would be called an induced false memory. It was found that participants who underwent a positive mood induction or no mood induction showed a higher susceptibility for recognizing lures as originally presented, whereas people in the negative mood condition showed significantly less of this false memory effect. The second experiment established that the difference was based in encoding of the items, with those in the negative mood relying on an item-specific strategy (Storbeck & Clore, 2005).
Linking familiarity with positive affect is highly relevant to déjà vu and mood. An experiment that used smiling and neutral faces showed that faces that have not been seen before but that were smiling were more often falsely recognized as familiar than neutral faces (Garcia-Marques, Mackie, Claypool, & Garcia-Marques, 2004). This finding suggests that the valence of the stimuli alone may induce a false sense of familiarity. Again, the positivity from the stimulus is used as information. It appears that analytical judgments are neglected when we feel good about something, and instead we focus on peripheral details such as the atmosphere (Talarico, Berntsen, & Rubin, 2009).
Taken together it seems plausible to hypothesize that déjà vu is indeed connected with positive affect, and positive affect is connected with less analytical judgments, and thus more false memory and familiarity effects. The positive affect may stem from different sources, it may be that individuals inclined to a more positive personality are predisposed to the experience of déjà vu, or that the stimuli elicit positivity themselves and that one experiences a false sense of familiarity then. We designed a study to test whether people in a more positive mood will make more memory judgment errors than those in a low mood. And secondly, that those people with a higher positive mood will report more déjà vus during the experiment compared with people in a lower mood.
Method
Participants
Participants were 42 (14 male, 28 female) students, both first-year students who participated for course credit, and volunteers. Participants ranged in age from 19 to 29 years (M = 23.0, SD = 1.95). All participants were enrolled as full-time students at the University of Groningen.
Materials
The materials used in this study for the mood induction included a video for the neutral control condition about how to paint a wall, and an assortment of shorter videos for the positive mood induction that aimed at appealing to both males and females. Videos were both seven minutes long. We decided to use them because they were found to be highly effective in inducing mood (Gerrards-Hesse, Spies, & Hesse, 1994). Further, two printed autobiographical questionnaires with six questions each, adapted from Gillihan, Kessler & Farah (2007) were used, and pens were provided. The first questionnaire asked personal questions such as “What was the best present you ever received? Please write a few lines about it; who gave it to you, for what occasion, and why was it the best present?” whereas the second questionnaire asked for neutral or mildly negative responses such as “When was the last time you had a cold/flu?” (see Appendix 1). A PANAS scale (Watson, et al., 1988) was included twice as a measure of the participant’s current mood: the first after viewing the videos, and the second at the end of the experiment.
Testing was controlled on a Windows computer using the program e-prime. Participants could respond by either using a keyboard or a labeled response box. Test stimuli consisted of a picture data set (Goh, Siong, Park, Gutchess, Hebrank, & Chee, 2004), which we adapted for our use. We composed two sets of 50 object pictures, and 50 background scenes for the processing phase. In the processing phases the two sets corresponded to two distinct conditions: the shallow block in which participants responded to shapes embedded in the pictures with a button press, and the deep block in which they had to reply to the question “Is it alive?” for objects, and “Is it a landscape?” for scenes (see Appendix 2 for examples). Picture stimuli were presented in a random order and in the centre of the screen. The stimulus was on the screen for 1000 ms, and only after that time had elapsed participants were able to respond.
In the test phase we composed images consisting of an object and a background scene. Pictures were taken from two sources: either they were completely new, and thus had not been presented earlier in this study, or they were old and had been presented in the processing phase. Consequently, there were four possible combinations: 1) new object new scene; 2) new object old scene; 3) old object new scene and 4) old object old scene. For each combination there were 25 pictures presented, with a total of 100 pictures in each of the two test phases. The university’s ethics committee approved of this study.
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