"The scent of youth pours out of the clean wounds of the tree" —Vasalis

The plasticity of poetic language lends itself to an adulterous interchange of fields of meaning between our different senses. About a deceased man, the poet Pierre Klemp knows that ‘today, he smelled at his girl for the last time.’ Consequently, with regard to language, synaesthesia is a type of metaphor which entails a transfer between the respective domains of the different senses. We remember the poet Paul Éluard’s dictum that "la poésie donne à voir" (poetry makes [us] see). It is evident that vision and hearing are the senses most often involved in synaesthetic metaphors, yet references to the sense of smell are not rare. But synaesthesia is not limited to the confines of poetry solely. The philosophies of Plato and of Pythagoras, for instance, deal with ‘the harmony of (celestial) spheres’. In the history of art, Symbolism was based on the assumption that all phenomena that are perceived by our senses correspond with each other and that these correspondences refer to a supernatural reality.

The fact that we brought up the subject of synaesthesia‚ within the context of language is not fortuitous. It is at the very level of language that we assess quite clearly how linguistic strata connected to sensorial perception exchange semantic characteristics amongst each other. In the expression ‘a loud colour’‚ we notice how the adjective explicitly confers the intensity of a scream to colour. ‘The golden sound of strings’‚ evokes a hard resplendence which corresponds with the sound of the bow as it starts to glide over tightly stretched strings, while, at the same time, the noble character of gold is being transferred to sound.

Synaesthesia as a topic in philosophy

"Das Sehen ist schon Theorie" —Goethe

In contemporary philosophy, the question of synaesthesia‚ enhances the complexity of the issue addressed by Ludwig Wittgenstein in his ‘Remarks on Colour’, namely, the genuine inadequacy of language to describe even the most evident of sensorial perceptions. In this treatise, Wittgenstein deals with the inaccuracy/inadequacy of descriptive words used by empirical psychology on the one hand, and colour sensations on the other hand. According to this linguistic philosopher, there is a wide gap between the ‘appearance’‚ of our psychological experiences and the logic of physical ‘being.’ Wittgenstein specifically points at conceptual confusion; since our experiencing of colour is indeed hardly, if at all, buttressed by the reality of physical objects. It is evident that the cones in our retina are sensitive to the electromagnetic radiation of certain wavelengths -these are called spectral colours-, but whether these cones are specifically receptive to the very three wavelengths which correspond with the three primary colours, as the theory of psychology of colour perception would have it, is perfectly uncertain, just as it remains unsolved what exactly happens in the interaction, to and fro, between the retina and the central nervous system. In other words, theories of colour stemming from the field of psychology establish an apparent standard which is, however, not anchored physical actuality, but is credited in culture -and/or its conventions- with veracity and is applied to, for example, colour photography and colour television (the chromatic diagram). In his ‘Philosophical Investigations’‚ Wittgenstein states it in this manner: "The correspondence, the harmony between thought and reality consists of the following: if I untruthfully state that something is red, then it consequently is not red. And if I want to explain the word red‚ as it figures in the sentence "that is not red" to someone, I will do so by pointing at something red." Wittgenstein emphasised the representative quality of thought, which is not the same as its corresponding quality. A representation appears to be something that is either in correspondence or at odds with the results of scientific research. If language is stumbling and faltering in its own speech when wording out something as evident -to our eyes- as a red spot, what then should Wittgenstein think when confronted with the phenomenon of hearing colours or seeing sounds ! From the point of view of objectivist thought -within which even the naming of the physical stimulations of each separate sense remains problematic- the very phenomenon of synaesthesia is something paradoxical.

However, in ‘The Imaginary’‚ by Jean-Paul Sartre we read: "As a result of a mescaline injection that I have had administered to me, I have been able to experience brief hallucinatory sensations which were characterised by their markedly oblique, collateral nature: in an adjacent room, somebody was singing and when I pricked up my ears in order to listen more attentively and consequently completely stopped looking in front of me -three small parallel clouds appeared in front of me which evidently disappeared as soon as I tried to seize them."

In other words, the phenomenological perspective is diametrically opposed to the formalistic-analytical approach of Wittgenstein’s thinking. In this context, Maurice Merleau-Ponty went to the greatest lengths. In his ‘Phenomenology of Perception’, he describes how the different senses are interrelated. Music, for example, ‘encompasses space and displaces it.’ To Merleau-Ponty, the sensorial experience does not constitute our first contact with the world, but an experience brought about by "natural perception which is enacted by our entire body in one instance and which opens itself to an intersensorial world. There is a primaeval stratum of perception that precedes the split-up into distinct senses". He argues that: "on this level, experience is so ambiguous that the rhythm of a sound brings about the merging of cinematographic images and creates space that allows for a perception of movement, whereas this succession of images would be too slow without this acoustic sustenance to evoke stroboscopic movement." He also refers to the experience under the influence of mescaline: Indeed, under the influence of mescaline, the sound of a flute produces a blue-green colour, the ticking of a metronome in the dark changes into grey spots and the spatial intervals of vision coincide with the temporal intervals of sound, the dimensions of the grey spot correspond with the intensity of the sound and the height of the location of the spot with the pitch of the sound. To Merleau-Ponty, however, the phenomenon of synaesthesia is not an otherworldly one that would only be brought about under the influence of psychedelic substances. Quite to the contrary, synaesthetic perception is the rule, not the exception. For every colour actually is the internal structure of the object as it reveals itself by externalisation. "The glitter and shine of gold shows us its homogeneous composition in a sensual manner, whereas the flat, dull colour of wood reveals the heterogenous nature of its fabric. The senses are interconnected by opening up to the structure of an object. One sees the inflexible and fragile character of glass and as it breaks with a crystal-clear creaking sound, this sound is -in its turn- carried by the visual quality of the glass." For very good reasons, the phenomenologist refers to the body as the general symbolical corpus of the world. Our corporeality is based on a generalised sensitivity to stimuli which opens a door via one of the senses. Even language is corporeal. Before a word is transformed into a concept, it is first and foremost a physical event. A word has a grip on the body upon which it acts and this hold is scanning in the semantic field that the word stands for. For words are indissolubly connected with what one says, what one hears, what one sees.

The psychoanalytical ‘in-sight’

"I hear you with my eyes"

Jacques Lacan takes up this symbolisation of thinking and elaborates thence. But to this structuralist psychoanalyst, the process of symbolisation in language does trigger or entail a break with corporeality. Language grants an in-sight. The synaesthetic experience is much rather based on the fact that our perception is already pre-mediated by language from the very moment of its inception. The sensorial input is fashioned and moulded by linguistic symbolisations which give way to associative condensations and displacements/shifts of meaning, in the same way as this occurs with the metaphorical process in poetry. We always perceive something in a sound or in an image which needs not necessarily be manifestly present in these. Perception never equals objective observation, but much rather a process of selection, attention and projection. In our desire to get to see what cannot be seen, we attempt to lift a corner of the veil. But the veil is sheathing something which is not there. The very thing we desire to see, is always bound to elude our vision. Pornographic images cater an incessant flood of images to eyes desirous to see what cannot be seen. Our sexual anatomy is serving fetishised objects to an invisible pleasure. Ultimately, sexual pleasure is the desire to be seen by those who provoke our desire. The look that is upon us when we want to see something. Like in the painting ‘Le viol’ (The rape)‚ by Magritte, featuring eyes in the place of female breasts, staring at the spectator, the vagina has become her mouth. This surrealist world constitutes an accurate depiction of the fact that things are not in reality what they are in our perception. As such, synaesthesia presents the fragmented relics of a phantasm: it seems as if, in the sexual experience, the senses of feeling, vision, smell, taste and hearing intermingle and blend into an amorphous mass.

Synaesthesia quintessentially is an experience in which language, the voice, resurfaces into the visual field. How are we to understand this ? According to Lacan, the gaze and the voice are -in addition to breasts, faeces and the phallus- two partial objects‚ of desire. This implies that the gaze and the voice do not respectively pertain to vision or hearing as perceptual procedures, but they much rather have to do with what‚ we see or hear. When we speak, we respond to a primordial address with the Other, but this mailbox remains empty. What occurs in psychosis, is the condition that this empty spot in the Other, in what we see and/or hear, becomes part of reality. The psychotic actually hears the voice of the primordial Other, and is aware of the fact that he is being relentlessly observed. To the psychotic, the voice and the gaze have become part of reality. But in the case of the average neurotic such as you and me, dear reader, the voice and the gaze tend to elude our experiences. The experience of a soundtrack that accompanies a silent film does not constitute a naturalisation, in the sense of a realistic imitation of life. Much rather, we are witnesses to a strange experience as we hear the voice of an invisible master. The Other speaks. Sound and vision do not complement each other in a harmonious manner. In our capacity of speaking beings, we much rather experience how our voice is detached from our body. When we see someone speak, we hear a ventriloquist. In his ‘Vorlesungen über die Aesthetik’‚ Hegel presents us in a certain instance with the example of an ancient Egyptian sacral sculpture which utters a deep resonating sound every morning at sunrise. This mysterious sound that emerges from an inanimate object is a good metaphor for the birth of the subject. The voice is mute and always resonates within a void. Man loses the immediacy of his experiences as a result of his accession to the symbolic order, i.e. his adherence to the order of language. And the very tone of his voice constitutes a lost object of immediacy. The tone is an elegy for a lost object. When this lost object comes too close to us, we are in a horror film. We take such pleasure in listening to music, because it prevents us from meeting the voice as an object. Beauty is outwitting us, it is a screen, a curtain that shields and protects us from a direct confrontation with the horror of the vocal object. The relation between voice and image can be described in the following manner: they relate to each other as a ‘figure’‚ does to the ‘background’. It is not so much silence that constitutes the background against which the voice emerges; it is much rather the figure of silence that becomes ‘visible’‚ against the background of the echo of sound. The voice is not only active on another level than the gaze, but it points at the hole in the field of the visible. In other words: we hear things precisely because we cannot ‘everything’! In the same manner, an image can emerge when a voice stammers, when the mouth ceases to produce any sound. ‘The Scream’‚ by Münch, for example, is mute‚ per definition. We hear the scream with our eyes. Let us consider the Testa di Medusa‚ ‘Medusa’s Head’ by Caravaggio. The scream of the Medusa is silent, her throat is seared up. ‘Hearing with your eyes’‚ is much more frightening than ‘seeing with your ears’. ‘To see with your ears’‚ does not only stand for fantasising, daydreaming and the like, but equally contains, for example, the rhythms of jazz as Mondriaan painted them in his Broadway Boogie Woogie. But Münch and Caravaggio present us with images of moments when the voice falters and fails. This form of ‘hearing with our eyes’‚ is at the same time a metaphor of the absolute silence of the heavenly spheres through which life moves about in the manner of a flying carpet.

Synaesthesia as a neuropsychological phenomenon  

In its physical, medical sense, the term synaesthesia refers to a complementary sensation: a form of perception that comes about without a stimulus to the sense that registers this perception and as a result of a different sensorial stimulation. ‘Auditio colorata’‚ refers to seeing colours when hearing certain sounds. ‘Phonism’‚ is an abnormal sensation, for instance hearing sounds when staring into glaring light. ‘Photism’‚ is an abnormal sensation of light, as occurs upon hearing shrill, piercing or loud sounds. Furthermore, restaurant owners know that people can smell certain foods upon seeing an illustration depicting a certain dish. Consequently, synaesthesia is the involuntary physical experience of a cross-modal association. The stimulation of one of the senses causes a perception in one or several senses. This neuropsychological interpretation attempts to locate the phenomenon of synaesthesia beyond the borders of metaphor, literary tropes, symbolism of sound and artistic multisensorial convergence. Considered from this angle, it is a function of the brain, occurring outside of the cortex in the left hemisphere. The hippocampus (a curved elongated ridge extending over the floor of the descending horn of each lateral ventricle of the brain) plays a quintessential role in the synaesthetic process. Synaesthesia only occurs with a select group of synaesthetes‚: at a ratio of 1 in 25.000 individuals, the overwhelming majority of whom are female, and the phenomenon would tend to occur more often with left-handed individuals. Synaesthesia most often occurs within families via either an autosomal or an X-chromosomal dominant transmission.

Synaesthesia functions as an aid to memory. For example, a synaesthete may state: "I know that it is 2 since it is white." It also enables them to remember the spatial location of objects. They show a markedly developed sense of order, cleanliness, symmetry and balance which is exemplified by their tendency to start work only when everything on the table lies where it belongs and is neatly ordered.

From the perspective of the organs involved in sensorial perception, an interesting problem surfaces in a comparative analysis of the respective spectrum of hearing and vision. The sensitivity of the human eye to colour is insufficiently developed to register the full and undeniably vast range of colours that exist in reality. The eye captures light, but light cannot represent all colours that feature in nature. We are unable to capture most of the vibration frequencies: they race past us, pass through us or are deflected by our body. Only frequencies between 430 and 750 billion vibrations per second stimulate our retina. This is what we call light‚: the rainbow spectrum of orange, yellow, green and blue. But what lies beyond these ? The lower frequencies are the infrared and radio-frequencies. The higher frequencies are the ultraviolet, gamma and X rays. But what would the glow of infrared be like ? How intense is ultraviolet ? We are not equipped to perceive the colour impression of radio waves. The tympanic membrane in our ear reacts to fluctuations in atmospheric pressure, with lower frequencies, but of an immensely larger divergence. We capture frequencies between 20 and 20.000 vibrations per second. 20 vibrations equal the deep primaeval bass growl of a Buddhist monk, pressing the holy ‘Aum’‚ out of the inner recesses of his body; 20.000 vibrations sounds as a razor-sharp shrill whistling. One octave on a piano keyboard is the interval between two pitches, the highest of which has twice the frequency of the lower pitch. We are able to discern a range of ten octaves. Within this tonal spectrum we hear the whispers of our beloved one and the roar of thunder. However, we ought to keep in mind that this wide range and broad differentiation on the level of hearing does not correspond to a comparably broad spectrum on the level of our vision. The interval between 450 and 750 billion vibrations does not even encompass one octave. What the eye is able to register is what our hearing captures between C and B-flat. Not more than that. In other words, our colour perception comes close to near-deafness. The range of audible sounds is larger than the palette of visible colours.

The aesthetics of synaesthesia: synaesthetics  

Synaesthesia often occurs with artistically trained individuals. Wladimir Nabokov, Olivier Messiaen and David Hockney, to name but a few, bear testimony to synaesthetic experiences. In other words, if we were to ask synaesthetes -thus, artists- to research the issue of synaesthesia in the field and the manner of art, we are bound to be presented with synaesthetics. Instances of crossover between the senses contain ample data for further experimental research. The artistic project synaesthetics‚ invites us to shift the boundaries of the senses by means of multimedia projects. Painting, graphics, installations, new media.... can all be marshalled to penetrate from the perspective of the visible into the total range of the sensorial field. Some more expeditions and research could be done on the domain of less explored senses such as haptic sensations and the sense of smell. Whereby we declare the hunt on sensorial interpenetration to be open.

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