Australasian Science: Australia's authority on science since 1938

Sleight of Memory



By John Bradshaw

Our memories can easily deceive us, for good or for ill.

Not long ago I came across a box of old possessions containing a picture book entitled My Farmyard Friends. My mother had sent the material years earlier when clearing out my juvenilia, and it had long languished until the time came for another generational spring clean. The book immediately evoked vivid recall of its pictures in the finest detail. It also brought back a much darker memory, but more of that shortly.

I was particularly struck by the fact that merely the physical presence of the book could provide sufficient context for the re-emergence of long-inaccessible associated memories that probably could never have otherwise re-emerged, no matter how careful and extensive the verbal prompting. Indeed we all know how finding an old theatre ticket in a long-disused suit can bring back many a long-forgotten emotional memory. Maybe we should hoard all of life’s trivia to recapture old loves, triumphs and disasters!

What was the dark secret associated with the children’s bestiary? Around the age of three my big toe became severely infected, with exquisite pain and impressive swelling and discolouration. In those late-wartime years in England, the family doctor visited you rather than the other way round. The toe was to be lanced, and to distract me I was presented with this wonderful new book to look at during the procedure. Not only do I remember that the procedure climaxed exactly at the page where a friendly old cart horse was hanging his head over a stable half-door, but also that I felt absolutely no pain whatsoever. In fact this realisation itself puzzled me, and actually made me naively aware of the power of distraction.

Fast-forward now to a few years ago, when I had to undergo a largely routine oesophageal endoscopy. This involves the examiner passing a scope down the patient’s throat to the stomach – potentially a thoroughly unpleasant experience requiring a level of “conscious” cooperation by the patient. In a world where date-rape drugs apparently permit sexual predators to make their victims cooperate to some extent, while subsequently retaining little or no awareness of what transpired, we can at least be grateful for the fact that similar partial anaesthesia permits the endoscopy patient to cooperate with the examiner while subsequently remembering mercifully little or nothing about the procedure.

In the anxiety-provoking minutes just before “going under”, I tried to distract myself by carefully reviewing a complex experimental design associated with a new research project. The room I was in, though fairly featureless like most such places, nevertheless possessed drapes of a certain shape and colour, and one or two obvious fittings. Suddenly, in the midst of my ruminations on experimental procedure, I became sharply aware of a complete change in the room’s layout; with a shock I saw that it had immediately become a totally different room while my thought processes had seemingly continued in an apparently seamless way across this instantaneous transition.

It was this last observation, rather than the realisation that the operation had been completed entirely without my knowledge but presumably with my full or partial cooperation, that most impressed me. Nor was I at all groggy on coming round – it was literally as if a section of my life had been neatly excised, and all cognitive processes equally neatly continued across the closed-up gap.

These two personal, almost everyday, instances illustrate two rather opposing memory phenomena – the power of context to cue the recall of very remote and otherwise inaccessible memories from extreme childhood, and the power of modern drugs to inhibit memory formation selectively without leaving a subsequent “gap” in the stream of awareness. Indeed some experimental success is recently being reported on possible procedures that delete pre-existing and unwanted memories (AS, April 2009, p.47), but that is another story for another time.

There is a clinical condition known as “dissociative fugue state”, whereby an individual may perform often quite bizarre (or even perfectly normal) acts in an apparently purposeful fashion with subsequent total memory loss or amnesia for the episode. Alcohol, physical or mental trauma may play a precipitating role. The state may or may not be accompanied by sudden loss of personal identity and all autobiographical memories. Significant distress may be experienced during or after such an episode.

As this article is an attempt to illustrate clinical memory and attentional phenomena with relatively benign examples from everyday life, let me recount my own experience of the clinical fugue state. In my mid-twenties I used to drive each day to and from my place of work along a featureless series of three-lane roads running through equally featureless countryside, the roads being punctuated by a regular series of roundabouts. In one direction I had to continue straight ahead across three such roundabouts and turn left at the fourth.

One day I suddenly realised, with something approaching terror, that I was in totally unfamiliar territory, without the faintest idea where I was or how I had got there. I knew nothing then about fugue states, not that it would have helped me. Pulling up in a panic, I gradually realised that the most likely explanation was that somewhere along the track, while preoccupied, I had inadvertently turned either at the wrong roundabout, or in the wrong direction, or both.

It seems almost a truism to claim that memory is a reconstructive process rather than something akin to making, storing and replaying a video clip. This was forcibly brought home to me some years ago when I participated, as a supposedly healthy control, in a study of individuals suffering from memory problems.

The actual procedure was not exactly novel, being borrowed from one developed by Elizabeth Loftus in her classic studies on the powerful effect of suggestion in recall. A video clip was shown of a minor traffic incident involving some superficial damage to a vehicle. The participants were subsequently asked either “How fast was the car going when it hit the lamp post?” or “How fast was it going when it hit the road sign?” In fact it had only hit one of these obstacles but participants, myself included, were quite sure, when subsequently asked, that it had in fact hit the obstacle mentioned, apparently almost parenthetically in the seemingly far more important context of its speed. We concentrate upon certain key features in a scene and fill in the subsidiary context.

Truly amnesic patients, and those suffering from dementia, may take this a stage further with frank, unintentional confabulation. I once studied aspects of short-term and long-term memory processes in patients suffering from Korsakoff psychosis. This condition, commonly caused by excessive alcohol intake and associated thiamine deficiency, affects memory circuits such as the hippocampus and temporal lobes. Old memories typically remain largely unaffected, but this is not he case for the formation of newer memories of events occurring after the onset of illness. The patients all seemed entirely rational – almost excessively so – and when questioned as to what they were doing in the hospital ward invariably confabulated that they were merely visiting friends, and soon would be returning home to eat with their spouses.

Similarly my mother, in her final years living in the family home, regularly claimed that all the neighbours, and in fact everyone in the street, had left, either permanently or on vacation, and that she was some kind of survivor in an otherwise empty world. Indeed, that was probably how it was for her. When we showed her the neighbour on one side washing his car, and the one on the other side mowing the lawn, she would rationalise that they must have come back for a while, though in a few minutes she would have again forgotten she had seen them and return to her solipsistic and lonely world.

Thus confabulation involves the generation of “fabricated” accounts of events or experiences, not necessarily deliberately or with conscious intent, to compensate for and make sense of the paucity of retained information in memory. As a form of “honest lying”, it illustrates the constructive nature of autobiographical memory – something that, in this era of “recovered memories” in the context of possible child abuse, we should always be aware of from a forensic viewpoint.

It is not just memories that may be selective and reconstructive. At a purely perceptual level we see largely what the context leads us to expect; hence we have difficulty picking up errors while proofreading. There is a phenomenon known as “change blindness”, a dramatic demonstration of which involved aficionados of a ball game watching a particularly exciting stage in the proceedings, at which point someone dressed in a gorilla suit strolled across the field. Few of the avid spectators even noticed the intruder.

Many years ago, during my doctoral research, I was measuring pupillary changes in the human eye that typically accompany cognitive processes and variations in information processing load, superimposed upon various background light intensities. We had an eminent visitor to the department, a specialist in hypnosis and hypnotic suggestion, and we thought it would be interesting to “suggest” to experimental participants that the brightness of the background illumination was rhythmically fluctuating up and down in synchrony with a rising and falling tone. In fact it remained constant. In those to whom the hypnotic suggestion was made, pupillary dilations tended to track the auditory tone. I often regret not having followed up that “quick-and-dirty” pilot study with a properly controlled experiment, but unfortunately our eminent visitor, who alone could make the hypnotic suggestions, did not stay long enough.

Suggestion, however, may have a powerful influence in the clinical context of the placebo effect. A placebo is an assumedly inactive substance or procedure, and is used as a control to serve as a baseline for comparison with an active treatment of interest. Thus a new drug is typically trialled, blind to both patient and administering physician, with half the patients merely receiving an inactive placebo. If the patients subsequently shown to have received the active substance improve compared with those on the placebo, the drug is deemed to be potentially efficacious.

The problem is that even placebos can have positive and beneficial effects if the patients believe in them, as they usually do. Thus there can be both behavioural and brain-activation changes, indicating cognitive and emotional benefits in depressed and obsessional patients on a placebo. Moreover, in a study of Parkinson’s disease, where the neurotransmitter dopamine is produced in insufficient quantities in certain neural circuits, placebos temporarily improved both dopamine levels and clinical state.

This situation may partly underlie recent concerns that expensive anti-

depressants, sometimes with unwanted side-effects, may be no better than placebos. Thus depression is indeed notoriously susceptible to at least temporary amelioration by suggestion, cognitive behaviour therapy and other non-pharmacological interventions.

If placebos can benefit, what about the possible powers of suggesting the opposite? This is the “nocebo” phenomenon. While the Latin placebo literally translates as “I shall please or help”, nocebo means exactly the opposite. Indeed, as we all know from everyday experience, telling someone that a procedure may lead to unpleasant consequences often leads to self-fulfilling prophecy, at least in the eyes of the beholder or victim.

Plato was undoubtedly correct when two-and-a-half thousand years ago he cautioned against blind trust in the simple evidence of our senses. The evidence is rarely simple.

John Bradshaw is Emeritus Professor of Neuropsychology at Monash University. This is an edited version of a script broadcast on Ockham’s Razor.