This primary iconism is an indefinable parameter: it is, to repeat a question posed by Wittgenstein (1953 §50), like asking the length of the standard meter bar in Paris. Obviously the bar is exactly one meter long, since it represents the parameter on the basis of which we establish lengths according to the metric decimal system. Naturally, in the case of the standard meter bar we can elude this self-predication by applying another parameter and measuring it in feet and inches.
But in the case of primary icons it is not possible to shift to another system of qualitative measurement, because even though there is another one, it does not exist on a perceptual level, as when we interpret colors according to wavelength. On a perceptual level you cannot predicate anything of a Likeness other than the recognition that it is that Likeness. We may later say we were mistaken; the perceptual impact of a color can be modified by setting it alongside another color, but in that case we would simply be choosing one Likeness in place of another. Therefore this innate experience of likeness cannot be used to judge similarities, and rules of similarity cannot be used to define primary iconic likeness.
But we must get back to the old dispute, and to the reason why attempts were made to shift likeness wholly onto similarity. There was a tendency to favor iconographic techniques, whereby (to return to the classic example in Gombrich 1956) Diirer’s rhinoceros had scales in accordance with a cultural type, while little attention was paid to the fact that, while today it strikes us as a quasi rhinoceros, we are nevertheless unlikely to take it for a crocodile.
6.6 Outlines
One example of iconoclast vehemence was the polemic about outlines. I am going to quote myself again, because it is not a good idea to reprove others for carelessness or errors that we may have committed along with them. In La struttura assente, I held that we cannot say that hypoicons have the properties of the objects represented, because if I take a sheet of paper and draw the profile of a horse, the only property that the pictured horse has (the continuous black line) is the only property that the real horse does not have. Therefore I would not have reproduced so much as the conditions of the perception.
The problem of outlines was taken up again by Hochberg (1972), Kennedy (1974), and Gombrich, who had become critical of his original conventionalism (1975). While it was usually held that there are no lines in nature and that outlines are therefore a human artifice, observed Gombrich, psychologists now tend to deny that their comprehension must be learned just like any other code. Outlines are a perceptual surrogate and serve as indicators of discontinuity. He notes that outlines can serve as an anticipation of the parallax effect of movement, because the objects within our reach will always detach themselves from the background but maintain an intrinsic coherence even if we move our head slightly (1975). In other words, if, on looking at a horse standing against a landscape, I move my head or change my position, I see other aspects of the landscape that I did not see before, while the horse is still the same: and therefore the drawn outline accounts for this perceptual «boundary.» 14
Already in A Theory of Semiotics (3.5.2), taking my cue from some observations made by Kalkhofen 1972, 1 returned to the topic of outlines (this time of a hand). Again it was denied that the hand possessed the property of having a black outline, but it was granted that, if the hand were placed on a clear surface, the contrast between the edges of the body that absorbs more light and what reflects the light can generate the impression of a continuous line. I was picking up the idea of surrogate stimuli, already proposed, as we shall see, in La struttura assente.15
But before we move on to surrogate stimuli, it is worth reflecting a little more on what it means to say that outlines are given in nature.
Let us consider the «ecological» version of Gibson’s psychology, according to which the object seems to have some privileged features, which directly excite our nerve cells, with the result that what we grasp of the object is exactly what the object preferentially offers us. In this regard, Gregory (1981: 376) observes polemically that to assert that all the information necessary for perceiving the environment—without the intervention of any interpretative mechanism—reaches us in the form of light stimuli that are already objectively organized would mean returning to the theories of perception prior to Alhazen’s and Alkindi’s observations on light rays, in other words, to the notion of «simulacra» coming from the object. We would still be adhering to a medieval idea of an intellect that grasps of the object precisely what counts for most in the object, its essential skeleton, its quidditas.
But the admitted seductiveness of Gregory’s argument is no proof that it is correct. As a matter of fact, nothing forbids us (in principle) from thinking that the ancients were right and that Gibson is right in returning to them.
I think there is a difference between saying that outlines are already offered by the stimulating field and saying that the stimulating field offers the object in a definitive way, already wrapped to determine our completed perception, which simply recognizes and accepts what has been offered to it through the senses. This difference concerns the moment Peirce thought of as that of primary iconism, or of what he called the percept, and the completed perceptual judgment.
Hubel and Wiesel (1959) and Hubel (1982) tell us that in perceiving a stimulus, our nerve cells respond to an optimal orientation that already exists in the stimulus. After inserting tungsten microelectrodes in the brain of a cat, Hubel and Wiesel were able to ascertain which cells reacted to what stimuli, and proved that the animal, when shown a blot moving across a screen, reacted more to movement in one direction than to movement in the other. But that’s not all.
At a certain point, while a slide was being placed in the ophthalmoscope, the cat reacted with a sort of instantaneous cellular explosion: it was ascertained that the reaction had nothing to do with the images on the slide but with the fact that, on entering the machine, the slide had impressed the shadow of its own border on the cat’s retina, and that was exactly «what the cell wanted.»
Now, these data tell us how sensations are received, but it is doubtful whether they can tell us how perception works. They tell us that cats (which cannot have been infected by iconoclastic idealism) do not receive an uncoordinated mass of sensations but are led to focalize certain features of the stimulating field at the expense of others. But is this due to the way the object is made or to how the cat is made? Psychologists are very cautious about drawing conclusions from these experiments. We can easily accept that when a cat sees a table, it is struck more by the luminous incidence at its edges than by other aspects of the surface, and that it is the same for us: but from this to go on to state that the same process is prolonged (in us and in cats), always through the initiative of the object, all the way to the higher levels of perception, is another kettle of fish altogether.
True, Hubel maintains that our cortical cells respond poorly to diffuse light, with the result that, when I look at an egg against a dark background, the cells concerned with the central area of the egg are not stimulated, while those stimulated by the borders of the egg respond. But right after that, Hubel concludes: «How the information from such sets of cells is assembled at subsequent stages in the path to build up what we call percepts of lines or curves (if indeed anything like this happens at all) is still a complete mystery» (1982: 519). Quite rightly, conclusions on the level of a theory of perception are not drawn from data on the modalities of sensation, and the experimenter does not risk stating that therefore knowledge is a mirrorlike correspondence and not also a construction.
In referring to the research carried out by Hubel and Wiesel, Johnson-Laird reminds us that «trying to understand vision by studying only nerve cells, as Marr remarked, is like trying to understand bird flight by studying
