The story goes something like this. I've been unmasked as an intellectual fraud, shipped back to my home town where it's been discovered that I never actually completed my high school degree, and I'm then forced to re-enrol as a thirty-something-year-old senior taking basic courses in the revised curriculum. The academic year whizzes by and now I'm smack in the middle of finals week, realising in a panic that I've either missed a critical exam or failed to study for it. And now, ironically, despite the fact that ‘technically' I already have a Ph.D., and even with all the turgid prose and arguments I can muster, I'm apparently not even intelligent enough to graduate from high school.

I've experienced this same annoying dream, or some alternative version of it, at least once a week for many years now - probably since earning my Ph.D., in fact, in 2002. Now, as far as I know, I did graduate legitimately from high school ... barely. In a future post, I may talk at more length about the impostor phenomenon, a belief common among academics where, despite objective evidence to the contrary, one feels they have only achieved their success through luck, deception, or by duping the system.

In the present post, though, I'd like to tell you about a relatively new, empirically supported theory of dreaming that some scholars believe can account for this dream as well as similarly distressing dreams that you probably experience on a semi-regular basis too. It also can explain why recurrent dreams are usually nightmarish in nature, rather than euphoric and Bacchanalian in tone. (For me, rather unfortunately, such titillating scenes happen only once in a blue moon and are usually mired somehow in guilt anyway.)

Originally proposed by Finnish neuroscientist Antti Revonsuo, the Threat Simulation Theory, or "TST", holds that dreaming serves a biologically adaptive function because it allowed our evolutionary ancestors to simulate problem-solving strategies for genuine, waking life threats. Antonio Zadra, Sophie Desjardins, and Eric Marcotte of the University of Montreal, neatly summarise the central argument of TST this way: "By giving rise to a full-scale hallucinatory world of subjective experience during sleep, the dream production mechanism provides an ideal and safe environment for such sustained practice by selecting threatening waking events and simulating them repeatedly in various combinations." Although Revonsuo's theory was initially postulated for dreams in general, it has special relevance for recurrent dreams, argue Zadra and his colleagues, because these should capture the most salient threat themes jeopardising reproductive success.

Researchers in this area concede that the evolutionary predictions made by TST are not directly testable because we cannot gain access to the dream content of our distant ancestors. It would be nice, of course, if our australopithecine relatives had jotted down their nocturnal ruminations in trim bedside journals for dream researchers to study today, but as with any other evolutionary psychological theory, TST can be indirectly tested through the standard reverse-engineering logic of Darwinian adaptationist principles. What we should see in contemporary recurrent dreams, argues Revonsuo, are "threat scripts" depicting primitive themes of danger that would likely have been relevant in the ancestral environment. Thus, once you look past the specific cultural relevance of my warped "Strangers-With-Candy" nightmare of returning to high school as an adult, what's lurking beneath the storyline's surface is a deep-seated threat to my status and reputation, aspects which are central to the biological success of all social primates.

In a 2006 article published in the journal Consciousness and Cognition, Zadra, Desjardins, and Marcotte performed a content analysis on a set of 212 recurrent dreams reported by participants ranging from 18-81 years of age. Among their findings, the authors report that escape and pursuit themes were the most frequent type of threat found in their sample of recurrent dreams (25.9%), followed by accidents and misfortunes (19.7%), aggression and violence (19.0%), physical difficulties (17.0%), emotional difficulties (7.5%), and disasters (3.4%). Furthermore, in nearly all cases the dreamer him- or herself (rather than a stranger or loved one) was the specific target of the threat and usually the dreamers actively participated in some way to resolve, escape, or combat the threat.

Also in the majority of cases, the dreamer did not suffer any loss due to the threatening event, or the loss was minor. (In my recurring dream, it usually ends with me convincing myself that at the end of the day I still have a Ph.D., thus all my anxiety is for nought and I wake up with a sigh of relief.) Yet as the authors note, whether or not one resolves the threat during sleep may be inconsequential if simply reflecting on the simulated episode upon waking concurs biologically adaptive benefits. There is some evidence, for example, that recovered alcoholics and former smokers who dream of falling off the wagon and giving into their vices experience such negative nocturnal emotions that these nightmares actually support abstinence in real life.

So, what do you think, is there any truth to the Threat Simulation Theory of dreams, or is it one of those "Just So" stories that some critics of evolutionary psychology believe are concocted, groundless tales of human nature?

According to Zadra and his colleagues, one major finding from their study of recurrent dreams failed to support a prediction made by TST. This was that fewer than 10% of all dreams analysed involved "realistic and probable" threats that could be translated to biologically adaptive behaviour in the real world. It's unlikely, for example, that I'll be hauled off to repeat my senior year of high school, so what's the adaptive use of my mind going over this silly scenario like a broken record, week after week?

Here's what Revonsuo and his colleague Katja Valli have said in light of this finding: "...fantasy-based threats can activate the threat perception and avoidance mechanisms in a relevant manner, just as effectively as reality-based simulations. For dreaming to function as an efficient threat simulation it makes little difference whether it is a realistic wolf or a werewolf chasing you in the dream."

And then there's the issue of my other recurrent dream of being chased around the neighbourhood by a monster-sized albino snake while people in their homes are slamming their doors shut on me and closing their blinds. But maybe that's for a different post...