The study of synesthesies - intersensory connections in the polymodal perceptive system - is a bright example of the infinite 'dramas of ideas', happening in the study of man - the most complex natural object ever known. The investigation of that psychic condition began to proceed, with difficulty, step by step, about 100-120 years ago, inspired by the public manifests of French and, after them, Russian poets-symbolists. They claimed the creation of new form of art, based on "melting of senses" and, in particular, "color hearing" ("'A' black, 'E' white, 'I' red…" in A.Rimbaud's poem; "the dawning, blue sound of the flute" in K.Balmont's verses). At the same time, positive sciences joining to the discussion of this unusual incomprehensible phenomenon, discovered something abnormal about it, not only from the artistic, but also from the point of view of psyche studies.

By the way, this discussion has much in common with an old one, evoked by rather unimportant case of color hearing - a statement of a certain blind Sounderson who lived in XVI century - that "the sound of trumpet seems scarlet to him". The list of world-famous thinkers who responded to that casual phrase is striking - J. Locke, "Essay concerning Human Understanding", 1690; G.W. Leibniz, "New Essays on Human Understanding", 1704; A. Shaftesbury, "Characteristics", 1712; D. Diderot, "Letter on the Blind", 1749; E.B. Condillac, "Traitu des systumes", 1749; A. Smith, "Of the External Senses", 1757; I.G. Herder, "Treatise on the Origin of Language", 1772. Philosophers in those times examined psychological problems as well, because psychology did not exist yet as separate science. It is remarkable, that all of them took the mere figurative phrase (just notice the word 'seems') as direct evidence of actual (!) seeing of color in response to the sound.

The acquaintance with the above works has convinced us that philosophers' interest in that particular fact was not incidental. It was inspired, first of all, by the constant search of new arguments in the heated discussions about sensationalism (the problem of objective character of our sensations; the sufficiency and hierarchy of sensory organs; their unity and the ability to substitute one another; their relation to consciousness and so on). And sometimes such keen interest for the possible abnormal "mixing of senses" together with its inadequate evaluation, would lead to general doubts in the primacy of the objective reality over the consciousness. In most obvious form it had been demonstrated by the physiologist J. Muller, who, on the base of such 'co-sensations' as a tooth-ache caused by scratching against the glass, put forward an idea of 'specific energy of sensor organs'. Later on this idea was a starting point for H.Helmholtz's epistemological 'hieroglyphs' concept that runs counter common sense. If such a great mind might fell a prey to prejudice, then what about the average men, blinded by the extravagant synesthetic verbiage of the poets, often using it for claiming their own exclusiveness or simply for shocking the "hopelessly sound" bourgeois?

Although since the end of XIX century many scientists assumed associative-productive origin of synesthetic compaisons in culture and art (V. Ivanovsky, P. Sokolov, L. Sabaneyev, N. Pern - in Russia; T. Ribot, A. Binet, E. Claparede, T. Flournoy, Ch. Rossigneux, V. Segalen - in France, and many others), there still remained some prejudice against the long ago compromised concept of the "association of ideas" (characterized by J. Locke as "some sort of madness"). This made some researches to seek for more 'reliable', more 'scientific' explanations of synesthesia, 'color hearing', etc. - as a rule, in the physiology of higher nervous activity. Some supporters of 'anatomic concept' supposed that, for example, Rimbaud's 'color hearing' or Scriabin's correspondences between color and tonality occurred due to 'short circuits' between different sensor 'lines'; some others believed that nervous stimulation could be transferred between the auditory and visual areas of brain (I. Baratoix, A. Benua - in France; F. Mendoza - in Spain, G. Lomer - in Germany, and others).

Close to that views was 'ataviatic concept'. According to that, all 'synesthets' just retained, in rudimentary form, the initial 'integral sense' supposedly inherent in all human beings at early stage of growing up, both in onto- and phylogenesis. (M. Nordau, R. Valaschek, G. Werner - in Germany, and others). And some researches attempted, already in these early times, to give sort of neuro-physiological explanation, suggesting certain cerebral structures responsible for such 'mixing of senses' (a summary of these hypotheses is available in later Russian editions, see [1, pp.64, 74; 2, p.54]).

What accounts for paradoxical fact, contradicting even to plain logic, that synesthesia is considered simultaneously as a miracle, and as anatomic or psychic abnormality, that is, in the end, as 'useful illness'. Judging from the psychological dictionaries, such absurd situation remains up to now!

As it appears, let's repeat once more, the abnormal synesthesia (in a form of actual co-sensations) really exist, having a status of very rare psychic phenomenon. It can be characterized as an obsessive, unintentional, invariable psychic condition (by some assumptions, even inherited and genetically determined condition). Some researchers specially note, that this form of abnormal perception - they call it 'constitutional synesthesia' - can be evoked (modelled) in normal subjects under certain conditions, for example, sensory deprivation, meditation, epilepsy, and, with more guarantee - by drug influence, which may cause besides hallucinations also real 'co-sensations' [3, p.30].

There are known less dramatic forms of synesthesia, first of all, 'color hearing', which can be considered, by their obsessive character, as some sort of abnormality, acquired in the course of maturation, although not nestled on the anatomic level. Such sort of synesthesia usually appeared in a childhood as a result of casual intersensory associations (associations by contiguity). And had they been connected with a strong emotional experience, they would be fixed in memory, ousted to subconscious level and stay their for life as some kind of 'dear neurosis'. For example, a grown-up man would ever see the name 'Julia' in yellow color just because his first love in early childhood used to wear yellow dress. Russian psychiatrist I.Yermakov at the beginning of XX century was the first to explain the neurotic origin of such synesthesies, claiming his discovery as "the brilliant victory of Freud's concept" [4, p.268].

Naturally, such synesthesies are more frequent than 'constitutional' ones, but they still belong to a number of marginal phenomena that would distort the understanding of synesthesia as a normal psychic condition. Already in 1930-s the scientists had become definite in discerning of associative synesthesies, which play big role in everyday communication, culture, and abnormal or 'constitutional' synesthesies. The latter were referred to 'clinical' cases (with reason) by the outstanding German researcher of that period A.Wellek. As if in revenge, today's researchers refer the normal common case to 'pseudo-synesthesia', with a negative air on it, counter to 'constitutional' synesthesia which seems more interesting to them.

In spite of remaining confusion with the discerning of normal and abnormal case of synesthesia, the studies of normal synesthesia's manifestations (most interesting case, serving important functions in culture) were going on successfully. Among the marked achievements in that field are: an ascertainment of the regularities in the intersensory correlation by 'semantic differential' method (which was specially developed to study 'color hearing' phenomenon (C.Osgood [5]); classification of the most common synesthesies in everyday language (L.Marks [6]); a study of metaphoric synesthesies and their functions in the art (B.Galeyev [7]).

As it happened, for many years the studies of synesthesia were conducted rather by the linguists, art critics and musicologists than by the psychologists. But since the 1980-s the burst of interest to the very nature of synesthesia is observed in Western countries (in USA first of all). During this last period the attention is focused exactly on the abnormal, 'constitutional' form of synesthesia (being considered as a 'true' form of it). The boom was produced by the emergence of new tools in neuro-physiology and neuro-psychology: electroencephalography, computer tomography, etc, which allowed the researchers to consider the results of their studies as more reliable.

All that could be just greatly appreciated. More than that, were these new technologies used correctly and adequately, under the supervision of science considering a man as an integral whole, surely they would help, at last, to draw a definite line between normal and abnormal cases.

But it turned out otherwise. Some researchers, seized with euphoria by the potentialities of new technique, restricted themselves in the study of 'constitutional synesthetes' only, using tomography method to trace in minute details their 'movement of thoughts'. They believed, this would help them to approximate to the understanding of 'color hearing' nature - the unique gift, which 'great synesthetes' Rimbaud, Rimsky-Korsakov, Scriabin, Kandinsky, Chiurlionis and Messiaen supposedly possessed of [8]. Once again the same situation as in the end of XIX century repeated - and again it's not only excessive claims which are faulty, but also unjustified involving of all these famous names to draw more support to (let me say it) their poor understanding of the nature of 'color hearing' inherent in the musicians and painters (see about it [9, 10, 11]).

Let's remind that prominent Soviet neuro-psychologist A.Luria was the first to point out in 1970-s the cerebral areas which probably have something to do with the origin of 'constitutional' or abnormal synesthesia (he never studied other cases). To his opinion (which could not be corroborated by direct measurements in that time) synesthesia occurs "on the level of upper tube and sub cortex area" [12, p.21]. (By the way, he applied his speculations, rather mechanically, to A.Scriabin case!).

American psychiatrist R.Cytowic continued the cause began by A.Luria, using Single Photon Emission Computerized Tomography (SPECT) to locate areas in the brain, responsible for synesthesia origin. He dealt with only 'constitutional' synesthesia condition, too (considering A.Scriabin a 'constitutional synesthet'). SPECT method involves the introduction of radioactive xenon 133 into the blood flow. It is believed that any change of neural activity in certain cerebral area is accompanied with the increase of blood flow through that area, and consequently, the increase of xenon-133 radioactive emission in this spot. The latter effect can be located and measured, enabling scientists to study the working brain of the 'synesthetes', exactly in that time when they actually experience synesthesia. Such experiments were conducted by R.Cytowic and showed remarkable "shut-down of the cortex" in synesthesia condition. This made him think the 'limbic system' (ancient area of the brain) to be more likely place for synesthesia origin. Similar inhibition of the cortex is observed in other conditions: free hallucinations, drugs intoxication, eideticism and other forms of hypermnesia. This proves once more (for all R.Cytowic's objections) that 'constitutional' synesthesia' belongs to a number of deviations from the normal cerebral activity. To R.Cytowic's opinion, all sensations are firstly processed by the limbic system unconsciously, in blended, integrated form. Their differentiation into separate species such as visual, tactile, etc. sensations occurs at the next stages. Now, in case of 'constitutional synesthetes' these processes in the limbic system may be released, come into consciousness and experienced as synesthesia. Basically, we are all 'synesthetes'; the difference is that 'constitutional synesthetes' are aware of their initial, blended form of sensations, while the rest do not. Thus Cytowic has indirectly supported the 'atavistic' concept of synesthesia popular at the beginning of XX century [13, 14] and referred 'true synesthetes' as 'cognitive fossils'. I think that in this case 'blended' are not the sensations themselves, but their protopathic components, which excessive intensity would cause such deviations from the norm.

English scientists S.Baron-Cohen and J.E. Harrison, using more complex method (Positron Emission Tomography, or PET) studied marginal case of 'color hearing' (obsessive involuntary 'seeing' sounds in colors). They assert that the origin of synesthesia is determined by the direct links between two cortical areas, processing visual and auditory information [15].

H.M. Emrich from Hannover Medical Institute has concluded that synesthesies are determined by the cortical areas communicating through limbic structures [16].

Scientist V.S.Ramachandran from the University of California sees the mediator of sight and hearing areas in the cerebral zone called TPO (a junction of Temporal, Parietal and Occipital lobes) which proceeds "cross-modal synthesis of sensations" to build the integral image of object. He also produced some evidences that the mechanisms responsible for metaphoric thinking and synesthesia share one and the same cerebral zone. At the same time he proved the real sensory nature of the extreme links of synesthetic associations chain [17].

P.Grossenbacher also seeks the origin of synesthesia at the genetic level, yet he prefers functional approach. He supposes that synesthesia is caused by the incorrect work of the brain, rather than anatomic anomalies, pointing out that this condition can be evoked by enough dose of drugs. Obviously in that case the additional pathways can't be grown in a moment. As it is known, brain contains multi-sensory areas which process information received from specialized single sense areas. There exist also 'feed-back' pathways running from multi-sensory back to single sense zones. In normal condition these feed-back links are inhibited. Grossenbacher believes that in synesthetic brain this inhibition might be reduced resulting in the experience of synesthesia [18].

As we can see, all these explanations differ one from another appreciably. Maybe, it's just because the researcher study different things, using different methods. So the dispersion of estimated portion of 'constitutional synesthets' in the population is not surprising. 120 years ago Bleuler and Lehman cited the figure 12%; Luria (studying, in fact, only isolated cases) - 50% for children and 15% for adults. More strict in the estimation of 'constitutional synesthetes' ratio were R.Cytowic - only 1:100000 at first, then increased to 1:25000; Baron-Cohen - 1:2000; Emrich - 1:1000; Ramachandran - 1:200. All researchers emphasize that the number of female 'synesthetes' far exceed that of male's (with male/female ratio 1:10 by Baron-Cohen and 1:3 by Cytowic). The latter also reported higher rate of left-handers, homosexuals and artists among the 'synesthetes'.

Judging to all, the situation here changed only slightly since the end of XIX century, when synesthesia admirers collected synesthetic cases, ranking Rumbaud and Scriabin with the notorious Sounderson from XVI century or housewives who shared their 'dear neurosis' with everybody around them. Articles were being published under the titles such as "One more possessor of 'color hearing' is found - a peasant from Bavaria", or "an Eskimo from Greenland", or "an Indian of Pueblo tribe" and so on. The present situation simply looks more reputably and more striking to the average man, as it involves fascinating things - computers, magnet-resonance tomography and so on. It's not surprising then, that quite a few Synesthesia List's members (web forum held by the American Synesthesia Association) express distrust and negative attitude to many scientific data a-la Cytowic, when they are applied to the synesthesies borne by the culture and functioning within it.

Let's remind that the revival of interest to the psychological problems of synesthesia in 1980-s - with a predominant reductionism approach - has been provoked not only by the emergence of new neurophysiological methods. Synchronically it was stimulated by the needs of quick-growing new-media industry - the formation, on the base of computer technologies, completely artificial audio-visual realm (various kinds of multi-, hyper-, inter-media, virtual reality). Man-programmer actually plays a role of 'Creator' of this new medium, trying to make it in most optimal and harmonic form, adapted to human perception. Naturally, designers' attention has been turned to synesthesia phenomenon. One would think, modern research technologies should be applied, first of all, to study intersensory links and the laws of normal form of synesthesia, as the most adequate to the task.

But the present situation in that field makes us recall the parable about a man who is seeking for the lost coin under the street lamp, only because there is enough light for him…Alas, almost every Western conference on synesthesia turns into one more 'party' of 'constitutional synesthetes'. Respectable scientific editions give space to their tiresome self-observations; neuro-physiological laboratories conduct experiments with the same contingent, examining fanciful, casual manifestations of 'color hearing' of abnormal or neurotic origin (colored vowels, letters, names, days, months, etc). According to such synesthetes' own admissions, their experiences show no conformity to any definite law. As for suggested neuro-physiological mechanisms of synesthesia, the discord is observed in that field too. It seems that the lack of conformity in the synesthetic correspondences suggests the great variety of possible causes for their origin (and vice versa).

Not long ago my favorite international journal 'Leonardo' for the Arts, Sciences and Technology has announced a discussion on the implications of synesthetic correspondences in multi-media projects. You can imagine my shock when I saw synesthesia being defined in this announcement as 'brain anomaly' [19, p.162]. The author had to break in with the Open Letter [20]. This letter set out, in short, the same arguments as presented here in detailed form. Praise God, after that the references to 'brain anomaly' had vanished from the discussion. It's a pity I have not recall then, to the point, one joke of the above-mentioned remarkable researcher of synesthesia, A.Wellek, whose name is consigned to oblivion for some reason. As early as in 1931 he wrote: "trying to find any regularities of intersensory connections on the basis of clinical synesthetes' evidences is the same as putting the question of ghosts reality to the vote in a madhouse" [21, p.352].

To work out practical rules for polymodal multimedia synthesis it would be better to examine 'common synesthesia' evidences supplied by language and art. That does not matter if the internal psychic mechanism of this phenomenon is not quite understood yet, for it can be taken as 'black box output'. Since synesthesies functioning in the culture, fit everyday communication so well, one could expect some general laws at the bottom of it. Any casual, senseless deviations inevitably would fall out, unable to stand practical test. That is why we always pointed out that synesthesia fixed in language and literature is an excellent 'laboratorial material' at hand to study these laws [22, p.72]. The same relates to the sounding material of music, more precisely, musicological texts [23, p.181] which often involve synesthetic comparisons to describe certain features of music. For better understanding we give here some examples of, first of all, audio-visual (i.e., synesthetic), most general, common correspondences [24, p.50]:

A study of cultural inheritance would help to reveal some concrete correspondences existing in human psyche - for example, between certain timbres and certain colors, tonalities and colors (see about it [25]).

Strict adherents of neuro-physiological methods in synesthesia studies reject apriori such successive approach, referring 'subjective' introspective methods as obsolete. Getting bored with behaviorism, they give definite preference to the 'objective' instrumental procedures. Let's repeat, we are not against such instrumental support, but - if to take up the profound Wellek's joke - not for the purpose of registering the presence of colored ghosts in a dark room by means of modern computer technologies.

One could agree, after all, with the proposals like that: "Post-mortem examinations would allow closer inspection of what's different about synesthetes' brains… But, so far , no known synesthetes have died and left their brains to science" [26, p.35]. But is it possible, let us ask, to consider poet Rimbaud, painter Kandinsky, musicians Scriabin and Messiaen as candidates for such 'post-mortem examination'? To mix their 'color hearing' with brain abnormality is as incorrect as to compare poetical imagery with clinical hallucinations.

As we can see, the studies of synesthesia are focused now mainly on the analysis of abnormal deviations of the intersensory connections. Yet when the results of this analysis are extrapolated incorrectly to the manifestations of synesthesies of cultural origin, it is itself an example of 'anomaly' in the process of scientific cognition - as far as psychology and epistemology are concerned.

REFERENCES

[1] Kravkov S.V., "An interaction of the organs of senses". - Moscow, 1948, pp.64,74 (in Russian).

[2] Blinova M., "Musical creative work and the profession of a musician". - Moscow, 1974 (in Russian).

[3] Cytowic R.E., Wood F.B., "Synesthesia". - Brain and Cognition, 1982, v.1, No.1, pp.23-35.

[4] Ermakov I.D., "Synesthesies". - In: Transactions of the Psychiatric Clinic of Moscow University. - Moscow, 1914, v.2, pp.249-269 (in Russian).

[5] Osgood Ch., Suci G., Tannenbaum P.H., "The measurement of meaning". - NY, 1978.

[6] Marks L.E., "The unity of senses". - NY, 1978.

[7] Galeyev B.M., "The co-operation of senses and the synthesis of arts". - Moscow, 1982 (in Russian).

[8] "Richard E. Cytowic M.D. interviewed by Jas. Morgan: Synsory overmode". - Mondo-2000, 1994, No.12, pp.77-86.

[9] Galeyev B., Vanechkina I., "Was Scriabin a synesthete?". -Leonardo, v.34, 2001, No.4, pp.357-361.

[10] Vanechkina I., Galeyev B., "'Color hearing' in Rimsky-Korsakov's creative work". - In: "Russian music of XVIII-XIX centuries: culture and traditions". - Kazan, 2003, pp.181-195 (in Russian).

[11] Vanechkina I., Galeyev B., "Color hearing of the musicians: myths and reality". - In: Annual of Russian Psychological Society: Proceedings of the III All-Russian congress of psychologists. - St.Petersburg, 2003, v.2, pp.11-15 (in Russian).

[12] Luria A.P., "Sensation and perception". - Moscow, 1975 (in Russian).

[13] Cytowic R.E., "Synesthesia: a union of the senses". - NY, 1989.

[14] Cytowic R.E., "The man who tasted shapes". - NY, 1993.

[15] Baron-Cohen, Harrison J., "Synaesthesia: classic and contemporary readings". - Oxford, 1997.

[16] Emrich H.M., Schneider U., Zeedler M., - "Welche Farbe hat der Montag?". -Stuttgart, 2002.

[17] Ramachandran V., Hubbard E., "Hearing colors, tasting shapes". - Scientific American, 2003, No.8, pp. 47-53 (USA).

[18] Grossenbacher P.G., Lovelace C.T., "Mechanisms of synaesthesia: cognitive and physiological contents". - Trends in cognitive sciences, v.5, 2001, No.1, pp.36-41.

[19] "Synesthesia special project". - Leonardo, v.31, 1998, No.3, p.162.

[20] Galeyev B. "Open letter on synaesthesia". - Leonardo, v.34, 2001, No.4, pp.362-363.

[21] Wellek A. "Zur Geschichte und Kritik der Synasthesie-Forschung". - Archiv fur Gesamte Psychologie, 1931, Bd.79, S.325-384.

[22] Galeyev B.M., "Literature as a 'laboratory' of synesthesia studies". - In: "Inter-disciplinary connections in literature studies". - Saratov, 2003, pp.33-38 (in Russian).

[23] Galeyev B.M., "Light-music: the formation and the content of new art". - Kazan, 1976, p.181 (in Russian).

[24] Galeyev B.M., "Problems of synesthesia in the art". - In: "Art of shining sounds" (collected articles). - Kazan, 1973, pp.67-80 (in Russian).

[25] Galeyev B.M., Vanechkina I.L., "'Color hearing' and 'affect theory'". - In: "Languages of science - languages of art" (collected articles). - Moscow, 2000, pp.139-142 (in Russian).

[26] Carpenter S., "Everyday fantasia: the world of synaesthesia". - The Monitor of Psychology, v.32, 2001, No.3, pp.26-29.