Deja Vu Effect

How can deja-vu effect the

When I teach memory to my undergraduates, I point out that one of the leading theories of memory retrieval and the very nature of memory itself hinges on what it feels like to access memories. Some information feels like it is being remembered, whereas other information comes to mind as a fact. Likewise, when making judgements of whether we’ve encountered something before — recognition — we can sometimes retrieve specifics to justify our endorsement of prior occurrence, or other times we can be certain we’ve encountered the information before without retrieving such context – our recognition is driven by a feeling of familiarity. I’ve made a career out of researching such feelings – and when they go wrong, such as with deja vu – and I have a lot invested in it. In short, I think that memory is guided by subjective states which operate at retrieval. As I am teaching, having outlined this theory, I like to pause at this point and ask how we might measure such subjective feelings as experimental psychologists.

I tell them that the simple answer is that we can just ask the participant in our experiment to tell us what they think or feel*. In the 1980s, according to some of my elder and better colleagues, this came as something as a revelation for the experimental study of memory, and was even viewed as something of a return to introspectionism. I didn’t know all that when I started a PhD looking at subjective evaluations – metacognition – in Alzheimer’s disease. Alongside advances in patient-centred care, it seemed a reasonable thing to do to ask patients to gauge their own memory capacity, and the measures yielded sensible data and meaningful results, if you got around the fact that the accuracy of such metacognitive evaluations was plagued by floor effects for the memory task. Likewise, the classification of recognition memory responses according to subjective states yields replicable and robust effects. Levels of processing manipulations effect the experience of ‘remembering’ in a predictable fashion, for instance, as I tell my students.

Anyway, my career developed to include the study of deja vu and delusional states of familiarity. Deja vu, it should be noted, is a subjective experience par excellence. Because of the earlier work on subjective experiences of memory and the mainstream use of subjective reports, it has become acceptable to just ask people about the states they are experiencing. Again in the 1980s, we started ‘inducing’ Tip-of-the-Tongue (ToT) states by merely administering a set of tough general knowledge questions and asking people if they had the answer on the tip of their tongue (it might be nice in this era of embodied cognition to see if there actually IS something on the tip of the tongue). Some experimenters do neat things like look at the susceptibility of having another ToT after having just had one, or the reaction time to respond to a question the trial after reporting a ToT, but such things are rare. As you might have noticed, ToTs vary with age (but how they differ seems to differ in the lab and the real world) and other ‘objective’ factors like that – all that helps us triangulate on what such states are, and more importantly, it helps us know whether we actually are measuring something real but intangible . Nonetheless, you can never really know if someone is experiencing a ToT or not. Likewise for deja vu – as we (the handful of deja vu researchers who will assemble shortly for the first time at ICOM 6) are found of saying – it has no behavioural corollary.

The holy grail of deja vu research is the experimental induction of the experience. A few sensible, apparently testable theories of deja vu formation exist, and so we should put them to the test. If we know what causes deja vu, we can provoke it in experiments. Clearly the most compelling and elegant of these experiments have been run by Anne Cleary, and they represent the very best we have in understanding deja vu-like illusions of familiarity. We are probably all searching for the paradigm which does for deja vu what the DRM did for false memory, but I don’t need to go into any detail here about the experiments carried out on deja vu because what I am addressing here is something more fundamental than that: can we trust someone’s judgement when they report having had a deja vu experience?

All of which is a necessarily long preamble to describe what seems to me to be the culmination of my research work so far, five well-powered experiments (or four experiments and 2B) run with somebody else’s graduate student, Radka Jersakova at the University of Leeds (hard-working first author) and my own ex-student Akira O’Connor at the University of St Andrews (hard-working senior author). These data have just been . It seems to me they raise some very alarming issues about subjective reports in cognitive psychology.

A long time ago, when I still lived in the UK, we started out with the aim of measuring how we asked questions about deja vu influenced the report of deja vu. It seemed to us that in our own experiments and in those published elsewhere, it was pretty easy to generate deja vu. Or at least, it was suspiciously too easy to have students report they were experiencing deja vu. Or at the very least, it was relatively easy to have students report that they were having what they thought to be deja vu experiences. These tortuous sentences underlie the whole problem of subjectivity (we shall come to this later): is what I say is deja vu the same as what you say deja vu is? More importantly, how could we know we were really giving people deja vu? I suggest that if we were really capable of reproducing the intensity and strangeness of the deja vu experience in the laboratory, then we should probably have a few spontaneous reports of deja vu in our cubicles – and, probably, a long queue of eager undergraduates willing to do our experiments. We don’t have either.

In our PLOS ONE article we stress the fact that even in control trials (where deja vu is not supposed to be generated) reports of experience can be as high as 23%. We thought that the use of repetitive questions on each trial about deja vu were responsible for this high baseline report of deja vu and we were concerned that it would lead to the exaggeration of the real rate of deja vu, which is, admittedly, always significantly (in the statistical sense of the word) higher in the experimental condition. We were worried by the possibility of ‘false positive’ deja vu experiences – and thus a misunderstanding of what deja vu is.

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