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Synaesthesia, metaphor and right-brain functioning

by Patrick Martin


This essay examines the phenomenon of synaesthetic experience, its implication for conventional models of perception and the cognitive structure of the brain. It also proposes that there are similarities between metaphorical expression and synaesthetic perception in their formal deviance and their construction of single "images" by the use of forms drawn from two (or more) distinct conceptual fields.

Table of Contents

1: A brief exposition of the conditions and neurological activities which pertain to synaesthesia.

2: A case study of a synaesthete: Vladimir Nabokov.

3: How synaesthesia disrupts the notion of "perceptual modularity".

4: The election of feeling as an alternative mode of knowing within synaesthesia.

5: The structural and functional correspondence between metaphorical expression and synaesthetic perception, and their occlusion from structural hypotheses of operational behaviour.

A brief exposition

Synaesthesia might be described, metaphorically, as a confluence of two or more sensations derived from a single perceived datum. That is to say that the synaesthete experiences form (as in sound, image, smell, taste and touch) in more than one modality. The synaesthetic effect is most prevalent with written language; individual lexical items being associated with (or more precisely, experienced concomitantly and indistinguishably from) chromatic, phonic, tactile and olfactory sensations. An example of this is the almost universal agreement, amongst those who bear this ability, that "O" has a brown texture and "I" has a whitish hue.

Recent research expounds further upon this: Hubbard (1994) has found amongst subjects an association between light visual stimuli and high auditory pitch. Harrison & Baron-Cohen (1995) corroborate this link between audition and vision. Gilbert, Martin & Kemp (1995) record the robust correspondence between vision and olfaction.

The generative implications of this phenomenon are such as to disrupt the modularity framework with which cognitive science conventionally operates. It also questions the imputed hierarchical arrangement of the brain, within which the cortex has a favoured pre-eminence. The means by which research on synaesthesia tends to undermine this model shall be dealt with later. An account of the neurological activity that pertains in synaesthetic perception should thus provide a helpful preface to that discussion;

Synaesthesia has only received acknowledgement as a legitimate field of study in the last seventeen years and its corollary in some branches of cognitive sciences has been to modify extant models of cerebral activity. Positron emission tomography has revealed that during synaesthetic experiences there is greater activity in the limbic system, at the base of the temporal lobe. This biological positionning would implicate the involvement of a more emotive influence on the apperceptive functionning of synaesthetes (as the temporal lobe is responsible for emotion and memory), an hypothesis which is supported by the further discovery that during synaesthesia bloodflow (and hence neural activity) in the left hemisphere is greatly reduced.

As if to convince of their right temporal-lobe orientation, synaesthetics are predominantly (and on a statistical basis, overwhelmingly) left-handed.

The overwhelming majority of synaesthetes are women ( a ratio of 6:1 enjoys consonance across many studies (Motluk,1994),(Harrison and Baron-Cohen,1995)) and enjoy far-above-average memory faculties. These individual phenomena configure to suggest that, within the dichotomy of verbal understanding and feeling, synaesthesia exclusively pertains in the latter. An account for this, and its implications, shall be approached later.

Vladimir Nabokov: A case study.

Nabokov was a self-proclaimed synaesthete, recording that at five years of age he announced to his mother that "the number five is red"(Boyd,1991). His case is exemplary in that it is a verbal-chromatic kind and that it is seemingly hereditary: his mother too experienced synaesthesia which accords with Cytowic's research (1996, and cited in Motluk,1994) of intergenerational transference of ability. Nabokov's obsessive and eidetic memory and intense reverence for both his own childhood and the age of childhood is also a feature of synaesthesia. (Motluk, ibid.)

The correlation between synaesthesia and written language (in that their development seems synchronous) might be said to have a manifestation within his writing. The structural similarities between metaphorical expression and synaesthetic experience are discussed later in this paper but some instances of the transrational schema of sensations which Nabokov expresses will serve to partly illustrate this correspondence and to exemplify the manner in which the expression of this "neurologically real phenomenon"(Harrison & Baron-Cohen,1995) functions as a dynamic signifying element; one which transgresses semantic rules and works at a level of sensation and polysemous suggestibility.

These example are taken from "Lolita; or the Confessions of a White Widowed Male." (Nabokov, 1956).

1."a sigh of delicious relief"(p.105)

- A projection of alimentary sensations onto emotion.

2."sweet wetness" (p.112)

- A projection of alimentary onto tactile.

3."the air was warm and green"(p.116)

- A projection of visual-chromatic onto tactile.

4."Lo was listening in profile"(p.118)

- A projection of visual onto auditory.

5."A young golden giggle"(p.120)

- A projection of visual-chromatic onto auditory.

6."Her young silent hands" (p.120)

- Auditory onto visual-tactile.

What is brought to bear in these instances is a keen sensitivity to a non-modular perceptivity of sense-data, the visual, audible, and olfactory are recombined (in a way that is natural and unsuppressible in the synaesthete) to appeal to a sense that it is not operating under a strictly rational framework.

Nabokov studied partly in the Russian Formalist tradition which had as one of its tenets

"tearing the object out of its habitual context (thus achieving )...a heightened awareness of things and their sensory texture."(Ehrlich,1981,p.126).

This is a measured (although admittedly too reticulated) account of the effect of synaesthesia; it prerupts the accepted link between cause and singular perceptive effect (as in the air being both warm and green (ibid.)) which draws attention to the potentiality of modal experience to be gained from one stimulus. This in turn brings into dispute the conventional cognitive view of the modular link between perception and sensation.

Perceptual Modularity

Anderson (1985) accounts for visual and auditory memory as being of separate modules; they are stored separately in iconic and echoic memories respectively. The Gestalt approach to this phenomenon of reception is that there are organising principles which distinguish between sense data, and structure it accordingly for sensory input. In this conventional approach it is the cortex that governs the operation of these principles along programmatic lines, and guides data along separate neural modules.

In this model there is at work the notion of a division of labour; certain neural channels carrying only visual stimuli, certain others carrying auditory and tactile stimuli etc.For example Anderson describes visual information processing thus

"Light falls on the retina of the eye and is converted into neural energy by a photo chemical process. This information is sent by various neural paths to the visual cortex of the brain"(Anderson,1981,p.10).

What is posited from Cytowic's research on synaesthetics (1996 and cited in Motluk,ibid.) is that in their cases it is not the cortex that controls this distribution but the limbic system. The limbic system is thus said to determine the saliency of information being processed.

The underlying theoretical approach to the cortico-modular view of sensation is a rationalist one, one which has as its basis the excision of the emotive and (necessarily) the transrational.

Anderson writes that "To a large degree cognitive psychology has been engaged in a search for the right set of higher level concepts with which to describe human intelligence"(p.10,1981).

The procedure thus described is one in which extant verbalised frameworks are adopted in an attempt to offer insight into the non-verbal operations of the cognitive system. In this manner it is not discovery of phenomenological observables within the activity of the brain that influences theory and hypotheses but rather the availablity of rationally consonant scientific metaphors which shape the means by which human cognition is understood. For example in speaking of information processing Anderson draws an analogy between it and a postal service and uses the terms "channels", "centre", "pathways"; thereby engendering the notion that the brain operates with an immutable hierarchical system ("cortex"="centre") with a programmatic functional communication system to and from that centre. It is not the simple point that language can only fail to record truthfully the features of an extra-linguistic reality that is being made here, but rather that a science which operates with the precept cited, of a complacent linguistic determinism, has at its core a fundamental weakness in it approach.

It is precisely this tendency to adopt the available model which is most attuned to the notion of rationalist and cortical supremacy in cognitive activity that the study of synaesthesia challenges. The election of the limbic system as the focus of control is promoted in Cytowic's research (ibid.). Whereas Anderson records that information is processed and stored in a serial and sequential fashion within the brain Cytowic proposes that the study of synaesthetics shows that this is not the case and that neural impulses do not flow in a strictly linear fashion.

At this point the question of whether this putative challenge to the authority of the body of mainstream cognitive psychology is weakened by the fact that its contentions only pertain to a very small percentage of people should be addressed. Harrison and Baron-Cohen (1995) cite its instances as being one in twenty five thousand people , Cytowic claims it is at least one in two thousand. The simple promotion of the limbic system as the central assessor and dispatcher of information (to adopt Anderson's postal metaphor) in lieu of the cortex would seem to be misguided. What does seem to be evident from the research is that the integration of limbic and cortical systems (rationality and emotivity) within the cognitive system cannot be dealt with in the limited terms that it has. Their occlusion from the operations of one another in terms of perception and sensation, as dealt with in theory, mark the partial failure to view any kind of holistic integrated activity as being carried out by the brain.

Synaesthesia: Feeling as an alternative mode of knowing.

Within the psychoanalytical model of the self (or the two potentialities of consciousness) synaesthesia belongs to the pre (or un-) verbalised self in most aspects of its condition. Its physiological positionning in the right-hemispheral temporal lobe equates it with a diffuse attentional capacity; an awareness that is unpremeditated, unprojected. Matluk (ibid.) describes it as perception bared to consciousness. This is partly an expression of its irrepressible and unconscious nature (the twin association of sense-elements is unmediated, it seems, by conscious striving).

It also suggests a more integrated flux of memory, emotion and sensation than is posited within conventional cognitive science. What Claxton (1991 ) describes as the projection in desire is therefore absent.

Herman Hesse (cited in Claxton,199 ) has written that "everything is beautiful that becomes a clear object of contemplation"(P.213). This "clearness" must be seen as a perception that operates outside cultural bias, and is an attempt to forego the projective tendencies inherent in perception. Everything that is hypothesised about synaesthesia (its non-linearity of process, its non-modularity, its prevalence amongst women (and emotiveness) and its concomitance with childhood traits and exceptional memory capacity) tinge it with a pre-social, pre-symbolic operational tone.

The pure contemplation of the object of which Hesse speaks mirrors the formalist approach which was mentionned earlier. Formalism also stressed the importance of qualities of sound, stress and topography within poetry above its culturally contextualised semantic element. In synaesthesia the commingling of formal qualities (as instantiated in the Nabokov quotes) is contrastive to the staticity of verbal meaning.

All of this would seem to suggest that synaesthesia is somehow a shadow of a pre-lapsarian ( a "pure") consciousness; a diaphonous perception through feeling. This is partly corroborated by the points just elaborated but to accept this is to ignore the fact that synaesthesia is a product of symbolic and linguistic acquisition; developing at about five years of age in most cases.

It might be hypothesised that, although it is partly hereditary, synaesthesia is cultivated in a child as a receptive response to the immediate social environment. It is aided by the non-forcing of closure upon the stimulating capacity for the subject of the object. Nabokov's case more than attests to this. His childhood was almost idyllic in this manner, the acquisition of words and symbolic referents did no more than draw out the singularity of the objects to which they referred and his subsequent and individual pursuit of creativity was perhaps an attempt to re-furnish the object with its uniqueness intact, by refusing to accept the generic, categorisations of language (which draws strict distinctions between senses).

Nabokov also had an immense fastidiousness for specificity of detail (exemplified by his learning the latin species name of every butterfly extant) which itself bespeaks an attention, an unclosed receptivity to the objective that is present in synaesthesia as it is in the feeling self.


The Non-Constructivist Approach:

Within the study of metaphor the non-constructivist approach dismisses tropic use of language as deviant and illogical, since the model and rules of language with which they work do not permit of the comprehensibility of metaphorical expression. Metaphor can be defined summarily as the expression of similarities between dissimilars, in other words constituents of distinct conceptual categories are shown to bear similarities through metaphorical expression.

In a similar way the effect of the "Cortico-Modular" thesis of sensory functionning precludes the possibility of synaesthetic knowledge. As if suspecting the disingenuity of claimed synaesthetes Harrison and Baron-Cohen (1995 & 1996) have tested the modal association of subjects over long periods of time and found them to remain the same to a degree of one hundred percent (Control subjects scored 32%).

Thus the similarity ("of dissimilars") in sensory form that results from the study of synaesthesia is allowed no neurological reality within the model of the brain and is dealt with either by denying its legitimacy, dismissing it as statistically insignificant or accomodating it in a new and lesser model of activity. For the most part the latter option prevails.

In the study of metaphor the self-evidence of the legitimacy of metaphorical expression has resulted in a drive to integrate it formally into a model of language.

The theories of metaphor which most relates to synaesthesia are those of Paivio and Walsh (cited in Ortony,1995) and shall be discussed here.


It is not the perceptive qualities of synaesthesia that can be (is) deemed deviant by any "logical" framework, schemata or theory; only through the expression of it, through its verbal realisation can it become deviant. In this it bears absolute similarities to Metaphor. The standard theories on the systematic logic of metaphorical expression (Ortony,1995), propose a model of base and target domains i.e. the expression "The lecturer attacked the student's proposal on synaesthesia" uses the domain of warfare as a tenor through which the vehicle of the sentence can be understood.

The hierarchical distinction between the conceptual fields is somewhat spurious, and in an effort to equivocate more properly on the nature of metaphorical composition Paivio and Walsh propose that within metaphor

"disparate elements are combined in utterance to yield up more than the sum of its parts" (Ortony,1995,P:136)

In a related way synaesthesia can be understood as not merely a comparison or combination of alike modalities, but the re-begetting, through structural similitude and confraternity, of the sensual. The sensual is not conceptualised as five distinct and incomplete modes of knowing but as an overarching "something" which gives access to knowledge.

Paivio and Walsh write that through metaphor "knowledge is represented in visual and verbal modes"(ibid,P.137). That expressive form can suggest a transcendence of the systematically "literal" also provides an understanding of the way in which synaesthesia can be seen to show as spurious the verbalised form of a sensual reality and the dogma of rationality that feeling labours under.


(To prolong once more the comparison with metaphor)... Paivio and Walsh suggest that metaphors mediate structural correspondences between different conceptual fields (ibid.). It has been the contention of this paper that within cognitive science the study of synaesthesia serves the purpose of exposing the theoretical construction of those "different conceptual fields" which preclude any interdependence or interrelationship between one modality and another. The categories of the senses and the individuality of the modalities perceived have a very obvious basis in a bio-physiological reality, (for example retinal image-processing re-ifies the link between the eye and image-reception) but it is not this initial perception of sense with which the argument is waged.

Both the structural correspondences and distinctions which each sense may be said to bear to the others is one established solely in language and the conceptual frameworks that arise from language. The cognitive phenomena of synaesthesia highlight the rationalist precepts with which the model of the brain has been constructed and suggest that emotive, unconscious and pre-linguistic knowledge plays a more ordered part in the conscious operations of the mind.


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Nabokov, Vladimir,1959, "Lolita", Penguin Books, London.

Ortony, Andrew,(Ed.) 1995, "Metaphor and Thought", Cambridge Press, London

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