There are many common illusions to be found in psychology textbooks and books on perception. A number of excellent examples are included in the psychology section of the bibliography. Typical examples include the rabbit/duck (reproduced to the right), old/young woman alongside the heading to this section of the page, the reversing cube, vase/face (to the left), etc. In each case, although there are two possible interpretations, only one can be perceived at any moment in time. Such illusions do not need line drawings to be effective as the photograph of the vase illustrated below indicates. The reversible perspectives are just as strong.
This illusion also holds even in animated form as the animation below right indicates.
A simple example that requires no artistic ability to reproduce is the Muller-Lyer illusion. Here there are two lines of identical length with arrowheads at each end. The direction in which the arrowheads 'point' markedly influences judgement of length, such that the two lines seem considerably different in length. So much so, that one often needs to check the length of each line with a ruler to be absolutely certain they are the same length.
Another more intriguing example is the Kanizsa triangle (various examples below). The central area of this triangle appears slightly brighter than the rest of the page/screen and there is also the impression of a second triangle lying on top of the first. The slight brightness is perceived because (without any conscious thought) it is presumed to be a solid object partially obscuring a triangle. This area is therefore considered to be closer than the triangle and background. On the basis of previous experience everyone has learned that foreground figures ought to be brighter and this 2 dimensional representation of reality is actually perceived as if there were such an object present.
Adding additional (dark) features around the central area, as in the figure on right, enhance the perceived brightness of the central area. Similar illusions can be produced using curved rather than straight lines.
Try drawing this illusion yourself. Black figures on a white background produce the strongest effect. Producing this image on your own piece of paper reinforces the notion that it is an unconscious process that leads to perception of the bright area in the centre. Even though you know what you are doing and you know that the paper you are using is all the same colour you cannot prevent your perceptions changing. Once you have drawn the figure you cannot help but recognize a brighter area in the centre of your drawing. As in the illustration on the left, black on white produces an even stronger effect that black on blue.
Similar illusions can be produced using coloured lines against different coloured backgrounds. Although all four images shown below are drawn using straight lines in the larger images to the right of each pair the red lines are perceived as part of a circle of pinkish-red. Again the perception centres of the brain is 'constructing' what it thinks is 'out there' rather than allowing us to possess an accurate picture of reality. The brain 'thinks' this is a black cross with a (pinkish, transparent) circular disc covering the central area.
Only a few illusions have been shown here but you can find others on the Psychology page). These should be sufficient to indicate that when you look at ads, especially those with manipulative intent, you will only tend to note one aspect of the ad and not the component parts. Additionally, you will tend to make a decision about ambiguous information at a preconscious or unconscious level. You do not need to think about what you are doing.
These illusions indicate that what we 'see' is not a true reflection of what exists. We do not just record information as if our visual system were a piece of film. What we do is 'construct' our perception of the world on the basis of what is seen PLUS what we know about the world. Perception if thus more useful than vision but it is not necessarily more accurate.
It is at the level of (preconscious) psychological processes that semi-subliminal information is presumed to operate - if at all. For decisions to be made about semi-subliminal content some recognition must have taken place - and yet been discarded from consideration by conscious awareness. The classic psychoanalytic approach and Wilson Key would argue that the initial meaning (about sex, death, etc.) had been repressed. The more prosaic perceptual approach would simply argue that on the basis of probability, one is more likely to perceive that which is common, expected and known, rather than uncommon and unexpected.
Regardless of which explanation is preferred the consumer still needs to consider the ethical issues associated with presenting imagery or information at a level at which it cannot normally be consciously considered. The author considers this type of information to be manipulative in intent. It also denies the consumer certain of his/her rights concerning freedom of choice and control over their decision making.
For more information and examples of Illusions and their explanations see the Imagination page.
The previous section of this page indicated that decisions about ambiguous stimuli can take place without any conscious control. Viewing the illusions indicates that where more than one possible frame of reference exists only one can be attended to, even when the stimuli are presented clearly. When embedded stimuli are presented at a semi-subliminal level then it is unlikely that sufficient attention will be paid to the stimuli to cause any conscious conflict. However if one is to judge by the extent to which major corporations make use of embedded stimuli in ads, some recognition must take place before such aberrant semi-subliminal stimuli are disregarded in favour of the more obvious elements or recognition of the whole picture. If such preconscious recognition did not take place then the investment in the ads would be wasted.
This recognition need not involve a whole image, it may be only part of a 'jig-saw'. The word sex for example may be represented by incomplete letters or simply s and X. Symbolic images such as death masks or dogs may be merged with the background or be incomplete. Yet, in each case, the same process of perceptual decision making has to be run through in order to decide what is worth 'raising' to levels of conscious appraisal. Consumers tend to perceive the ad as a whole. But prior to this they presumably attempt to make sense of the contributory parts, including any semi-subliminal components on the basis of their previous experiences. Such experience includes decades of observing semi-subliminal ads and each of us presumably knows, almost intuitively, what an ad is supposed to 'tell us'. And we may respond accordingly.
There is some evidence to indicate that anxiety can be triggered by subliminal and semi-subliminal images in experiments. If anxiety can also be triggered by semi-subliminal aspects of ads then one need not acknowledge any psychological defensive strategy on the part of viewers to account for some of their behaviour. Tobacco and Spirits ads for example, seemingly rely upon viewers of their ads experiencing anxiety but using their products as means of allaying anxiety. Defensive psychological processes do not need to come in to the reckoning to account for commercial use of semi-subliminal ads.
Some viewers, according to Key, repress 'recognition' of semi-subliminal features. Here Key assumes that the Freudian notion of repression comes into play to 'prevent' viewers becoming anxious about distasteful material. Repression is an unconscious attempt to 'block out' recognition of something that is unpalatable or objectionable. This is markedly different from the suppression that occurs when one actively attempts to 'push something out of ones mind' e.g. a repetitive tune.
Clinical reports and personal observation indicates that certain individuals do not like to acknowledge the existence of semi-subliminal ads. Some, in fact, react vociferously. There could be a variety of reasons for such reactions. But, if they are doing so without any conscious awareness of why they are reacting in this way, then their behaviour can be interpreted as evidence for the existence of some form of defensive process such as repression. Such a mechanism might also account for some people being unable to recognize semi-subliminal aspects of ads, even when they are pointed out to them. However, it would be going far to far to state that the failure to recognize all semi-subliminal aspects of ads is dependent upon the activity of defensive mechanisms.
In most instances, it is much more likely that the failure to recognize semi-subliminal stimuli is due to weakness or inappropriateness of the semi-subliminal stimuli. That is, the semi-subliminal content makes relatively little impact when compared to the main content of an advert. Such arguments are promoted by experimental psychologists on the basis of experimental evidence. However, these experiments do not necessarily have ecological validity. They are carried out using unusual stimuli and unusual conditions. And they do not get carried out over an extended period of time. Advertising, of course, tends to be long term, rather than expecting immediate impact. And, as indicated above, failure to consciously recognize imagery does not mean that there is also failure to make a (minimal) impact. It is also notable that the largest companies have run (and continue to run) the longest running semi-subliminal campaigns. Long term use may simply be a reflection of resources or it may be an indication of what is required to influence sufficient members of the audience.
Writers such as Michael Billig also point out that as we learn our native language we also learn to control our use of that language and those aspects of reality that are pertinent to us. Failure to recognize semi-subliminal material may simply be a 'matter of choice', a preference to attend to certain aspects of the environment and ignore others, rather than repression in terms of active psychodynamic processes. However, even information that is supposedly disregarded, either upon an injunction as in a court of law or by preference when the argument does not appeal, tends to carry 'weight' when subjective judgements are made. Semi-subliminal images and messages may just manage to tip the scales in the direction of a specific product when no particular preference is held.
See the Frequently Asked Questions Page for further information
Last Revised: 3rd January, 2003