No matter how much information is in the light falling on the retinae, there must be a mental mechanism for recovering the identities of the things in a scene and those of their properties that vision makes explicit to consciousness. Without such mechanisms, retinal images would be no more use than the images produced by a television camera and, contrary to the naive view, they cannot see anything … These processes must rely on certain assumptions about the world. (Johnson-Laird 1988: 61)
Moreover, maintaining that the process from sensation to perception involves unvarying privileged patterns to which the brain (human and animal) responds in a constant fashion, and even fully accepting an ecological theory of perception (in its most brutal form: we see what is there, and that’s all), still tells us nothing about the hypoiconic modalities with which we artificially represent those same objects of perception.
The real crux of the misunderstanding yet again lies in the immediate passage from the primary iconism of perception (that is, from the evidence that relations of likeness exist perceptually) to an established theory of similarity, in other words, of the creation of the effect of likeness. Anyone who has ever visited a perfume factory will have come up against a curious olfactory experience. We can all easily recognize (on the level of perceptual experience) the difference between the scent of violets and that of lavender.
But when we want to produce industrial quantities of essences of violet or lavender (which must produce the same sensation, albeit a little enhanced, stimulated by these plants), the visitor to the factory is assailed by intolerable stenches and foul odors. This means that in order to produce the impression of the scent of violets or lavender, one must mix chemical substances that are most disagreeable to the olfactory sense (even though the result is pleasant). I am not sure if nature works like this, but what seems evident is that it is one thing to receive the sensation (fundamental iconism) of the scent of violets and another thing to produce the same impression. This second operation requires the application of various techniques with a view to producing surrogate stimuli.
Think, for example, of two schematic figures (in some perspective) of a cylinder and a cube.16 A naive iconist would say that they represent a cylinder and a cube exactly as they are; a supporter of the cognitive value of iconism would say (and we cannot disagree) that under normal circumstances—when the cultural inheritance is equal—the figures would allow a subject to identify a cylinder and a cube and to distinguish between them; the supporters of the natural nature of outlines (whose number I have decided to join) would say that the lines of the two drawings exactly circumscribe the profile by means of which the object presents itself to us.
But the representation is «good » from a certain point of view, and such is the function of all representations in perspective, whatever the projective rule applied. Perspective is a phenomenon that brings into play both the object and the position of the observer, and that position also has a role to play when a three-dimensional object is being observed. Therefore the hypoicon in some way transcribes these conditions of observation. But now let’s reflect on the fact that the straight lines that circumscribe the contours of the cylinder do not have the same semiosic function as those that circumscribe the surfaces of the cube.
The parallel lines that circumscribe the contours of the cylinder are surrogate stimuli that represent the way in which, from whatever direction we look at it, we will see the cylinder stand out against its background (the number of these lines, if we were to rotate the cylinder, would be infinite, and Zeno would admit that we would never stop seeing the cylinder’s infinity of outlines). The lines of the cube, on the other hand, represent not only the profile of that object seen from that point of view but also, at the same time, the edges of the solid, which remain as such, even though their perspectival relation changes, depending on the point of view we look at or represent the cube. In both cases, we are dealing with surrogate stimuli, but (again in both cases) these stimuli «surrogate» different phenomena, which depend partly on the form of the object and partly on the way in which we decide to look at it.
6.7 Surrogate Stimuli
It is not true that the iconoclasts took into consideration only the profiles of horses or fanciful rhinoceroses, without posing the problem of the immediate impression of likeness experienced by the observer when in the presence of a realistic or hyperrealistic image. In La struttura assente (1968: no ff.), I examined an advertisement showing a foaming glass of beer, which evoked a sense of pronounced coolness, because on the glass you could see a film of icy vapor. Clearly the image contained neither glass nor beer nor icy vapor: therefore it was suggested that the image reproduced some of the conditions of the perception of the object: where, on perceiving the object, I would have been struck by the incidence of light rays on a surface, in the image there were certain chromatic contrasts that produced the same effect, or an effect that was satisfactorily equivalent.
Therefore, even though I realize that what I see is not a glass but the image of a glass (but there are cases of trompe l’oeil where I do not realize the image is an image), the perceptual inferences I bring into play to perceive something (and certainly on the basis of previous cognitive types) are the same ones I would bring into play to perceive the real object. From the relatively satisfactory way in which these surrogate stimuli stand in for the effective stimuli, I will take the image either as a good approximation or as a miracle of realism.
Now, this idea of surrogate stimuli has frequently been asserted by various psychologists.
For example, Gibson (1971, 1978) has spoken in these cases of «indirect perception» or «secondhand perception.» Hochberg (1972: 58) says on several occasions that the scene represented by a picture is a surrogate, because it acts on the eye of the observer in a way «similar» to the real scene; that an outline is «a stimulus that is equivalent in some way to the features by which the visual system normally encodes the images of objects in the visual field» (1972: 82); that when a border between two surfaces appears in the visual field, it is usually accompanied by a difference in luminosity, and therefore an outline provides an index of depth insofar as it makes us perceive (in a vicarious fashion) the very border where the luminous difference is found (1972: 84).
Research by Marr and Nishishara (e.g., 1978: 6) on computer simulations of perceptual processes tells us that a scene and the drawing of a scene look similar to us, because «the artist’s symbols correspond in some way to natural symbols that are computed out of the image during the normal course of its interpretation.»
But there is no doubt about the vagueness of all these definitions (in which we frequently come across expressions such as «in some way»). More than explain how surrogate stimuli work, these definitions acknowledge the fact that they exist and function. We have to do with surrogate stimuli in all those cases in which the same receptors react as they would in the presence of the real stimulus, just as birds respond to decoy whistles or as a sound-effects expert in the radio or the cinema supplies us (through the use of strange instruments) with the same acoustic sensations we would experience on hearing the gallop of a horse or the roar of a racing car. The me chanics of surrogate stimuli remain obscure, also because these «surrogations» range from the highest of high fidelity, as we shall see, to a simple invitation to behave as if we were receiving a nonexistent stimulus.
The fact that—even though we do not know exactly how they work—there are surrogate stimuli is exemplified splendidly in Diderot’s pages on Chardin (the 1763 Salon):
The artist has placed on a table an old porcelain china vase, two biscuits, a jug full of olives, a basket of fruit, two half-full glasses of wine, a Seville orange and some pâté. To look at the pictures of others it seems that I need to have new eyes made; to look at Chardin’s, all I need do is keep the eyes nature gave me, and use them well … The thing is that the porcelain vase is porcelain; these olives are really separated by the eye from the water in which they float; should I wish to eat the biscuits all I need do is reach out and take them; all I need do is peel this orange and squeeze it, take this glass of wine and drink it, peel these fruits, take this pâté and sink my knife into it … O Chardin, it is not white, red, or black that you spread on your palette; it is the very substance of the objects, it is the air and the light that you gather with the tip of
