by Guy Claxton
Subliminal perception is hard to write about, because the relevant terms in the language are so muddled. It is symptomatic of our cultural neglect of the undermind that we have no word for ‘being influenced by something of which we are unconscious’. Although it may conflict with the way some people use the word, I am going to use ‘awareness’ to refer to the general phenomenon of ‘picking up signals’ from the environment (or from the body), regardless of whether they get represented in consciousness. And I shall reserve ‘consciousness’, and ‘conscious awareness’, for what appears before the mind’s eye. Thus, in my usage, there is nothing paradoxical about using the expression ‘unconscious awareness’ to refer to the state of being affected or influenced by some stimulation that is not itself present in consciousness.1
In 1989, Thane Pittman and Robert Bornstein of Gettysburg College in Pennsylvania conducted an experiment to investigate how people decide between job applicants. Students were given the job specification – for a research assistant in the psychology department – and asked to review the applications of two young male candidates (call them Tom and Dick), and to make a recommendation as to which should be appointed. In fact, the applications differed in only one salient respect: Tom had good computing skills, but was poor at writing, while Dick was the opposite. Each application was accompanied by a photograph of a (different) young man. Before they took part in this study, the subjects had been asked to help out with another short experiment on visual perception, in the course of which they were exposed to five four-millisecond presentations of either Tom or Dick’s face, accompanied by the word GOOD. An exposure of four milliseconds, under the lighting conditions used, is too short for any conscious impression to be gained. All the subjects saw was a tiny flicker of light, without any ‘content’.
The students were twice as likely to choose, as the best person for the job, the candidate whose face had been subliminally presented. If it was Tom’s face that had been projected, two-thirds of the students chose Tom over Dick. If it was Dick that had been flashed up, two-thirds opted for Dick. When they were asked to justify their decision, the subjects who had preferred Tom said it was because computing skills were more important for a research assistant than the ability to write well. The subjects who had chosen Dick said that anyone could learn the requisite computing skills, but to be able to communicate fluently was of vital importance.2
Pittman and Bornstein’s subjects are unconsciously aware of the face that was flashed too briefly for conscious recognition, and of the association between that face and the positive evaluation conferred by the accompanying word GOOD. We know that they are unconsciously aware by virtue of the fact that their actual behaviour cannot be accounted for in any other way. Of course, it is true by definition that we cannot ‘see’ the unconscious itself directly. We can only infer its presence from its influence on things that we can observe, in just the same way that a ‘black hole’ cannot be photographed, yet its existence, and its properties, are implied by the fact that light behaves oddly in its vicinity. Likewise, to see how subliminal perception works, we have to look at the way people’s actual behaviour, or their conscious thoughts, feelings and perceptions, are ‘bent’ by forces and processes that are themselves invisible.
Though there are many controlled studies of unconscious perception, we do not really need science to convince us of its ubiquity. We are constantly reacting to things that do not enter consciousness (though it takes an effort of will to notice the existence of things that one has not noticed). As you read these words your body is conforming to the chair or whatever you are sitting in or lying on, and you are adjusting your posture every so often in response to sensations of which you are usually unconscious. Your hands are responding to the size and stiffness of the book as you hold it and turn the pages. You may even, while reading, have the experience of realising that a clock is in the middle of striking the hour, and of being able to count up the number of unheard chimes that preceded your moment of ‘awakening’.
The classic example of unconscious perception is driving a car and suddenly ‘coming to’; you realise that you have driven for the last twenty minutes, absorbed in a conversation or a train of thought, without apparently – consciously – noticing anything at all of the road, the traffic or the operation of the controls. Consciousness has been absorbed in one world, while the unconscious ‘automatic pilot’ has been in quite another, coping very nicely on its own with roundabouts, traffic lights and pedestrian crossings. And the same ability to pursue flexible, intelligent routines, while being ‘elsewhere’, is manifest just as much in walking along a crowded street, doing the washing up, playing the piano, taking a shower or getting the children’s tea. The ability to do things mindlessly, even cognitively quite demanding things like chatting to a friend or giving a lecture, is notorious. (You may recall the old story of the vicar who dreamt that he was delivering a sermon, and woke up to find that he was.)
The automatic pilot is sensitive to what is happening, and how things are going, just as the computer that controls the real automatic pilot in a plane is sensitive. On automatic pilot we do not just respond like stupid robots; we respond appropriately, like intelligent ones. Or we do most of the time. Sometimes we are caught out, and then we have behaved ‘absent-mindedly’. You find that you are halfway to work before you remember that you were supposed to be going to the doctor’s. Or, in William James’ famous example, you go upstairs to change for the party, and suddenly realise that you are in your pyjamas and cleaning your teeth. Especially when ‘we’, that is, our conscious minds, are preoccupied, we may find ourselves pouring the hot water into the sugar jar or lighting the fire with today’s newspaper.
But when consciousness is not so totally obsessed, merely entertaining itself with a fantasy or a rehearsal, then we do find that the unusual breaks through, it ‘grabs our attention’ and we wake up. A ball bounces out from between two parked cars just ahead, and suddenly we slow down and are on the alert for the child who may be about to dash out after it. Consciousness is re-engaged with perception and action; the conversation stops in mid-sentence. But here again there is evidence for unconscious perception, for how did we know to lock consciousness on to just this small detail, out of the stream of impressions that is constantly flooding in? How is it, when we impulsively turn our head, or stop and listen for a moment, that we frequently find there is something there to be attended to? The faint, unrecognised night noises of a friend’s country cottage keep jerking me back from the edge of sleep; while the taxis that used to rattle past my London flat throughout the night left me unmoved.
The only possible explanation for these phenomena is that the undermind is keeping a continual check on what is happening below the horizon of conscious awareness, detecting what might be important or dangerous, and deciding when to butt in to consciousness with a ‘news flash’. Of course it does this fallibly. Sometimes it interrupts me with false alarms – the noise which wakes me is just the beams creaking, not burglars or a fire – and sometimes it fails to alert me to what matters. But its existence is all I am trying to highlight at the moment, not its omniscience. The movements of consciousness, and the pictures it presents, reflect, like the news flash on the television, the judgements of editors, and the alertness of reporters whose existence we must infer, but whose faces we may never see.
We are constantly reacting to things not solely in terms of what they are, but in terms of what we expect them to be. We prepare ourselves, physically and mentally, for what is going to happen next on the basis of cues that frequently do not themselves enter consciousness. While this process continues in a routine and successful fashion, it usually remains unnoticed. But it reveals itself through its errors. The first few times you use a moving escalator, getting on and off feels slightly peculiar. But when you are more experienced, your body has learnt to make a subtle set of adjustments to help you keep your balance, which are automatically triggered by the surrounding visual cues as you st
ep on to the stairs. Now, as you approach, as travellers on the London Underground frequently do, an escalator that is stationary, the same cues trigger the same pattern, and you initiate, at just the right moment, a delicate compensation for an acceleration (or deceleration) that, disconcertingly, does not occur.3
An even more compelling demonstration of the same effect is provided by the room that you may be invited to enter if you visit the Psychology Department at the University of Edinburgh. The walls and ceiling of the room are actually an upside-down box that is suspended from cables just above the ‘real’ floor. The gap between walls and floor is too small to be noticed. You enter the room, the door closes behind you – and someone outside pushes the ‘room’ so that it moves relative to the floor, and to you. This produces a visual perception that normally only occurs when you yourself are walking or swaying, so, acting on this unconscious interpretation, you ‘correct’ your inferred movement by leaning in the opposite direction – and fall over.
Unconscious preparation may be perceptual as well as physical. Give someone a large and a small tin that weigh the same, and they will tell you that the small one is the heavier – because it is heavier than expected, given its size. Someone brings you what you unreflectingly imagine to be a cup of tea – and the first sip tastes strange, before you realise that it is actually a cup of coffee. Once your expectations are recalibrated, then its taste, the very same taste, becomes reclassified as familiar and satisfactory.
We do not see or taste or feel what is ‘out there’; conscious perception is a useful fiction that misrepresents ‘reality’ in our own interests. As you read, your eyes are flicking along the lines of print in a succession of jumps and fixations – ‘saccades’ – yet what you see, consciously, is a whole, stable page of print. If you were to hold the book twice as far away from your eyes as it is now, it would hardly look any smaller, even though the image on your retina is only half the size. And though part of the page is (probably) falling on the ‘blind spot’ of the retina, you are not aware of a corresponding hole in the world you see. The undermind routinely makes all kinds of adjustments to the data it receives before it hands them on to consciousness – because it is usually advantageous to do so.
These everyday examples of unconscious perception often concern aspects of the world which are perfectly visible, audible and so on, but which, though they are registered by the undermind, do not make it into consciousness. They affect us, but pass unnoticed. Experimental studies such as Pittman and Bornstein’s, however, have tended to use stimuli that are themselves very faint or fleeting, on the borders of what is perceptible. Such situations demonstrate very clearly the nature of unconscious perception. And they have fascinated psychologists since the very beginnings of the scientific approach to the study of the mind.
In a classic study in 1898, for example, B. Sidis showed people cards on which were printed a single number or letter – but the cards were placed far enough away that his subjects were quite unable to read what was on them. Sidis reports that ‘the subjects often complained that they could not see anything at all; that even the black, blurred, dim spot often disappeared from their field of view’. However, when he asked them to name the characters on the cards, they were correct much more often than they would have been by pure guessing, even though that is exactly what they felt they were doing. Sidis concluded from his experiments that there is ‘within us a secondary subwaking self that perceives things which the primary waking self is unable to get at’.4
Even earlier, in 1884, philosopher C. S. Pierce carried out a series of tests with his graduate student Joseph Jastrow at Johns Hopkins University in America, in which they judged over and over which of two nearly identical weights was in fact the heavier. Again, despite the fact that their subjective confidence was effectively zero, they were able to do much better than chance would dictate. Over the thousands of trials on which they made complete guesses, indicating ‘the absence of any preference for one answer over its opposite, so that it seemed nonsensical to answer at all’, they were in fact correct between 60 and 70 per cent of the time. What was particularly interesting about their study was their recognition that these results were not just of curiosity value; they are of real significance for the way people operate in the world, for instance how we relate to each other. They wrote that:
The general fact has highly important practical bearings, since it gives new reason for believing that we gather what is passing in one another’s minds in large measure from sensations so faint that we are not fairly aware of having them, and can give no account of how we reach our conclusions about such matters. The insight of females as well as certain ‘telepathic’ phenomena may be explained in this way. Such faint sensations ought to be fully studied by the psychologist and assiduously cultivated by everyman.5 (Emphasis added)
Not only do they see the relevance of these findings for everyday life; they also suggest that people may increase their sensitivity to such faint sensations. Just as intuition can be educated and sharpened (as I argued in Chapter 5), so can one’s ability to make use of the mass of weak impressions that underlie – and are usually neglected by – our normal ways of seeing and knowing. It is as if the mind has two thresholds, one below which it registers nothing at all, and a second above which something becomes conscious. In between the two lies the demi-monde of the undermind in which impressions are active but unconscious. And Pierce and Jastrow’s suggestion is tantamount to saying that the distance apart of these two thresholds can vary, so that it is possible to increase one’s conscious sensitivity to what had previously been going on at an unconscious level.
An early demonstration of the power of unconscious perception to influence what does appear in consciousness was given by Otto Poetzl, a Viennese neuropsychologist working with casualties of the First World War. He tested a number of soldiers who had suffered gunshot wounds to the part of the brain which processes visual stimuli, the occipital lobe at the back of each cerebral hemisphere, and discovered something rather odd. They were effectively blind in the centre of their vision, yet if they kept their eyes fixed on a picture (which they couldn’t ‘see’), ideas and images would begin to come into their conscious minds which were clearly related to the ‘invisible’ picture. Associations to the picture would start to surface in consciousness not as features of a coherent visual perception, but as more free-floating and mysterious fragments. Poetzl wondered whether he could produce the same kind of effect in people with normal vision, and devised the following test. First a detailed picture was flashed very briefly, for just one hundredth of a second, in front of the volunteers. They were asked to draw whatever they could of what they had seen – which was usually nothing or very little. Then they were told (absurd though it may sound) to go away and to have a dream that night, and to come back the next day, relate their dreams, and draw any elements of their dreams that they could. When he analysed the records of the dreams, he found that they contained many fragments and associations of the original ‘invisible’ picture.6
Though these early studies were not as tightly designed as one might wish, the essential results have been replicated recently under more stringent conditions. Cambridge psychologist Mark Price, for example, has shown that people are able to ‘guess’ the category to which a word belongs, even though the word itself was exposed too quickly to be detected. If subjects are flashed the word ‘carrot’ subliminally, they may not be able to say what the word was, but they still have a better than chance likelihood of guessing that it was a vegetable. In one of his experiments, when the subject happened to be his brother, Price inadvertently replicated the Poetzl effect. At one point he flashed the word ‘camel’ which his brother failed to detect However, in the middle of the following presentation, the subject suddenly started chuckling to himself. When Mark asked him what was up, he replied that he was laughing because an absurd fantasy about camels had suddenly popped into his head ‘from nowhere’.
Similar effects ar
e obtained when stimuli are hard to detect, not because they are faint or fleeting, but because they occur in peripheral rather than central vision. John Bradshaw at Monash University in Australia has shown that we can unconsciously read words that are on the edge of the visual field, and that such subliminal perception will influence how we interpret what we are consciously attending to. He flashed people an ambiguous word like ‘bank’ in the middle of the screen, and simultaneously, at the edges of vision, he flashed another word, such as ‘money’, which suggested one of the two different meanings of the central word. Though they had no conscious awareness of the peripheral words, his subjects nevertheless tended to interpret the central word as meaning ‘financial institution’ rather than ‘edge of a river’.7 Information which is strong enough to exceed the threshold of awareness, but not to become conscious itself, is nevertheless able to influence what does appear in consciousness. As we saw with intuition, consciousness seems to demand evidence that is more definitive than does the undermind.
Another implication of the Pittman and Bornstein study discussed earlier is that, because subjects do not know how or even that they have been influenced subliminally, they are unconscious of the true source of their decision, and they are therefore unable to use consciousness to guard against the influence itself. They are susceptible to the subliminal message precisely because they do not know it is there. People may have many tendencies that they try to control or mitigate, but unless these are picked up by the ‘radar’ of consciousness, those controls may not be able to operate. Just as we saw with intuition, the undermind may work with a richer database than consciousness, but the tapestry it weaves may contain threads and assumptions that are false or out of date. This opens up the intriguing possibility that, by bypassing the checks and inhibitions of consciousness, a subliminal stimulus may actually have a greater effect on behaviour than one perceived clearly.
