Christopher Nolan’s ”Inception” is an engaging action film. But it is merely that: a film. Not even really a film about dreams. In fact, whilst I enjoyed the complex storyline immensely, I was a little disappointed that the film’s production team had not wanted the film to depict dreaming in an accurate way.

The notion of having dreams within dreams (which occurs in Inception on four levels within an enforced (drug induced sleeping state) forms the basis of the plot and allows characters to carry out various tasks at different speeds simultaneously. Multiple dreamers enter into one dream space via technology that supposedly administers a drug and monitors sleep state, which is led by one individual in each dream. This method allows for different people to enter into the “subconscious” minds of another.

The film attempts to acknowledge the multi-faceted nature of dreams: the changeable balance of uncontrolled behaviours, characters and settings with the more rational ongoing monitoring of one’s dream environment. As researchers and dream scientists we have evidence that dreams contain both of these features, although there is some disagreement as to how each of these predominate. Dreams are presented in Inception as containing both projections (presumably some reference to the Freudian unconscious, referred to as the subconscious) that cannot be controlled, as well as there being a high degree of problem solving, forward planning, dialogue and numerous other higher order cognitions and abilities that are typically characteristic of waking consciousness. On the one hand I am delighted that Inception implies that dreams can be so sophisticated, within an unpredictable and often attacking situation. Indeed research has demonstrated the high presence of threatening situations and stimuli within dreams and there is an increasing body of work that evidences how dreaming cognition is more similar to that of waking thought, than different. On the other hand it seems that the producers of the film did not consult any current research in creating a representation of dreams, as there are numerous inaccuracies in the film.

The main controversial aspect of the film that some viewers are accepting without question, is that more than one individual can enter into the same dream space at the same time. We call this “dream sharing”. Within Inception, this was coordinated in a supposedly controlled, technical manner (that was never described or explained, of course). As researchers we try to understand features of dreams and dreaming behaviours by conducting careful observations and manipulations, and analysing output as evidence for something specific. We have not been able yet to find a way of entering into an individual’s dream so we can measure it objectively. Does this mean that we can’t demonstrate evidence against the idea that shared dreaming can occur? Technically no, however we should always adopt the scientific approach of seeking evidence before making any assumptions at all. With the advance of brain neuroimaging methods I do not doubt that only a few years will pass before we are able to find neural correlates of particular features of dreams, such as vivid imagery, salient emotionality and specific high order cognition. However at present there is nothing at all to indicate that dream sharing can occur.

Of course more than one individual could dream about the same event, theme, emotion or feature at a similar time, especially if some feature of a shared environment has been incorporated into the dream (a background noise or change in temperature, for example). However dreaming is a unique process so each and every dreamer will add to a dream their own experiences, preconceptions, current physiological state such as awareness of self in space, emotions, fears and wishes. This not only makes the study of dreams rather difficult (and intriguing!), it also implies that shared dreaming is likely to be impossible.

Another feature of the film - the idea of dreaming within a dream - may well reflect something that is possible. Data illustrating the functioning of the brain whilst asleep indicates how particular cells within the hippocampus – a region associated with episodic memory (remembering experiences and contextual information) – fire in the same order, though at different speeds (increased speed) over different times of night. That is, within different stages of sleep. Therefore within dreams it may be possible for things to occur to the dreamer at different speeds and times to real-world time. Take the example within the film of a dreamer being woken by be thrown into a bath of water. In the dream, the individual incorporated features of the water for some time before the dream ended, i.e. he awoke. We may recognise this from our own experiences of incorporating an alarm sound into a dream scene and creating a reasonably lengthy set of behaviours around that one sound.

Inception raises interesting notions about features of dreams, even though these are not often represented in a manner in line with our own research findings. For instance, memories from the main character’s (Cobb) past are often integrated into the shared dream space in an uncontrolled, unwilling manner. Some of these memories are relayed in a precise way as they actually occurred in waking life. We know that in actually such replays only occur in rare circumstances and are typically characteristic of post traumatic stress disorder. The memories that have been incorporated into Cobb’s dream space were especially emotional and we know that emotionality of an event does influence the likelihood of memory incorporation. However in actuality only some features of memories are likely to feature in a dream, rather than every aspect of it, such as where it occurred, where it occurred, who was with you at the time, what you were wearing, what you said and what you felt. So in the dream some aspects will be familiar to us and we accept the mismatching dream environment without question, as in the majority of cases we are not aware that we are dreaming or that things are somewhat strange.

Another feature of dreams alluded to in the film concerns that of dream recall. We may be familiar with the sensation of a dream memory lingering with us, though remaining inaccessible. A common feature of dreaming is the rapid decay of a dream memory trace. This is so profound that many individuals remain convinced that they never dream at all. Within Inception, the vagueness of a dream memory is exploited to convince an individual that a previous (lower) dream layer was actually reality. The same individual suddenly seems able to retrieve memory details from that previous dream layer (within another dream), with effort. In actuality effort does not often increase dream recall. Only focusing on a dream experience soon after waking can allow the waking processes of the memory system to encode the dream sufficiently for later retrieval. Other attempts, such as by thinking over the dream in different ways later on, may allow a dreamer to supposedly retrieve information and features. However we have no evidence whatsoever to demonstrate that these individuals are engaging in anything other than confabulation. That is, the making up of information. Clinicians and dream workers therefore need to be most careful when asking individuals to engage in similar practices.

In summary, Inception is a watchable (although not entirely engaging) action thriller, exploiting the intriguing human phenomena of dreaming to provide a backdrop for otherwise impossible behaviours. Unfortunately this results in some unnecessarily gratuitous action, rather than an accurate depiction of dreaming. The film should therefore be enjoyed for its big budget blockbuster special effects and complex layered storyline, and any viewer should not question the fictional nature of the plot.

Dr. Caroline Horton, Senior Lecturer in Psychology and Dream Researcher, Leeds Metropolitan University, UK.