What is Synaesthesia?

‘What is Synaesthesia?’

Synaesthesia – (plural “Synaesthesiae”), comes from the Greek “Syn” meaning “union”, and “Aesthesis” meaning “sensation”; a person who experiences synaesthesia is refered to as a ‘synaesthete’, and whose experiences are ‘synaesthetic’, or which are perceived ‘synaesthetically’.

Synaesthesia is a “neurological condition” whereby an external experience or stimulation through one sense is spontaneously associated with an internal experience or perception through a different sense; i.e. at the point of which one of the five senses is aroused, two or more different senses respond, thus creating a multidimensional sensation. For example: most commonly, a synaesthete with grapheme colour synaesthesia will associate specific colours to letters and numbers; likewise, and more rarely, a synaesthete with lexical gustatory synaesthesia will experience tastes in the mouth when reading text. Although commonly referred to as a neurological condition, synaesthesia is not listed in either the “DSM-IV” (Diagnostic and Statistical Manual of Mental Disorders, 4th Edition), or the “ICD” (International Classification of Diseases), since synaesthesia does not, in general, interfere with normal daily functioning. Indeed, most synaesthetes report that their experiences are neutral, pleasant, and may even enhance their ability to achieve certain tasks, such as spelling, and creating works of art. Rather like colour blindness, or perfect pitch, synaesthesia is a difference in perceptual experience, and is, therefore, referred to as a neurological condition in order to reflect the brain basis of this perceptual difference. To date, no research has demonstrated a consistent association between synaesthetic experiences and other neurological or psychiatric conditions, although this is an active area of research.

Neurologist Richard Cytowic identifies the following diagnostic criteria of synaesthesia:
1. Synaesthesia is involuntary and automatic.
2. Synaesthetic images are spatially extended, (they often have a definite location).
3. Synaesthetic perceptions are consistent and generic, (i.e.. simple rather than imagistic).
4. Synaesthesia is highly memorable.
5. Synaesthesia is laden with affect.

Genuine synaesthesia is spontaneous, specific, consistent and durable. Those tested will report a perfect repetition of their experiences when tested again months later, often scrupulously detailed, particularly with regards to colour, where sometimes indefinable tones or patterns may occur. For example: the colour baby pink as seen by the non-synaesthete, may appear to the synaesthete with tints of orange, speckled with grey, arranged like a spider’s web, and vary in intensity from centre to edge; as opposed to a single block colour of a definite composition. To the synaesthete, their experience of having synaesthesia is simply a part of their individuality and personal identity, perhaps almost like a sixth sense; in other words, synaesthesia forms an important part of their daily experiences, just as seeing or hearing “normally” is to the rest of the population, and cannot be switched on or off as and when desired. Their hypersensitivity is a quality unique to each individual – no two synaesthetes will experience the same form of synaesthesia with the same intensity, nor will they report the same experiences of sensory activation from a single stimulus.

Synaesthete Pat Duffy explains:
“Other people don’t see what we see and they’re not convinced that we see it ourselves. But what each of us sees is the reality we know. I am no more at liberty to change the white colour of the letter ‘O’ than I am to change its circular shape: for me, the one is as much an attribute of the letter as the other.” (2001).

Until recent years, and prior to detailed research becoming publicized, synaesthesia was regarded by society as a superhuman ability, and in some cases, a taboo subject. The sheer suggestion that words could have flavour, and objects have personality, would appear to the non-synaesthete as incredible nonsense, and consequently, isolate the synaesthete from any social acceptance with overwhelming feelings of obscurity and even abnormality. Likewise, a genuine synaesthete will find it equally incomprehensible that not everyone will associate, for instance, colour with letters and numbers, as they may do. As a consequence, synaesthetes have felt compelled to withdraw and contain their experiences within themselves and their private space, and to keep their experiences hidden from the disbelieving society.

Neurologist Richard E. Cytowic explains:
“Synesthesia is “abnormal” only in being statistically rare. It is, in fact, a normal brain process that is prematurely displayed to consciousness in a minority of individuals. Despite keeping the experience private and hidden, it remains vivid and irrepressible, beyond any willful control.” (“Synesthesia: Phenomenology and Neuropsychology – a review of current knowledge, 1995).

The first report of synaesthesia is dated to the year 1812 (Georg T.L. Sachs’ Hochel & Milan, 2008),: “Historiae naturalis duorum leucaetiopum: auctoris ipsius et sororis eius” (“Natural History of Two Albinos: the author himself and his sister”). The term “synaesthesia” was being used by the polymath philosopher Charles S. Peirce before 1866. However, while he used it in a sense similar to how it is used today, he did not use it towards writing about actual medical cases. The first use in case report write ups might be from Mary W. Calkins, in 1894. Although synaesthesia was the topic of intensive scientific investigation during the late 1800s and early 1900s, it was largely abandoned in the mid-20th century, and has only recently been rediscovered by modern researchers. Psychological research has demonstrated that synaesthetic experiences can have measurable behavioural consequences, while functional neuro-imaging studies have identified differences in patterns of brain activation (Hubbard & Ramachandran 2005).

Neurologist and author Oliver Sacks explains:
“Twenty years ago, synesthesia – the automatic joining of two or more senses – was regarded by scientists (if at all) as a rare curiosity. We now must regard it as an essential, and fascinating, part of the human experience. It may well be the basis for human imagination and metaphor.” (2005).

As many as one in 2,000 people experience natural synaesthesia, (Baron-Cohen et al 1996; Simner et al 2006), and at the last report, as many as 80 different forms were recorded, (Dr. Sean A. Day April 2016), linking different senses or perceptions. Thus a synaesthete may associate texture with taste, smell with colour, and so on – any combination of the five senses is possible, and synaesthetes are reported to differ considerably in intensity of the experience (cf. Dixon et al. 2004). Some forms of synaesthesia are more commonly reported than others – around one in 5,000 associate colours with letters; as few as one in 15,000 will associate taste with touch. More rarely still, pain can cause taste or colour sensations for some people. (It should be noted here that these statistics are not solely reliable, and are variable subject to incidence). A small minority of synaesthetes experience multiple synaesthesia, where a single external stimulus will cause multiple internal sensory perceptions, providing them with an almost overwhelming sensory ‘identity’ for different concepts. For example: a synaesthete may experience both sound and colour when exposed to a particular texture; likewise, a synaesthete may experience both colour and tastes in the mouth when reading and writing.

Psychologists and neuroscientists study synaesthesia not only for its inherent interest, but also for the insights it may give into cognitive and perceptual processes which occur in everyone, synaesthete and non-synaesthete alike. This phenomenon has been discussed by scientists for some three centuries, but only recently during the mid to late 20th century has it prompted more curiosity and thorough research. Although there are still psychologists who believe that synaesthesia does not exist as a spontaneous experience, others are recognising proof that synaesthesia is an inbuilt neurological condition in its own rite. Tests have shown increased blood flow to those parts of the brain which deal with, for instance, colour and sound perceptions, when activated by an external stimulus such as text or music. Scientists have reported synaesthesia to occur in individuals who have suffered a sensory loss during life, such as blindness or deafness; as a result of brain injury or stroke; use of certain drugs, such as LSD; and through neurological change, such as migraine and epilepsy. It is believed synaesthesia also runs strongly in families, although there is no evidence that it can be passed from father to son, and may therefore be inherited as an X-linked dominant trait. Reports have shown this to be more apparent in left-handed females, although synaesthesia can be passed to either sex, and from generation to generation – “The regions of our DNA that wire some people to “see” sounds have been discovered. So far, only the general regions within chromosomes have been identified, rather than specific genes, but the work could eventually lead to a genetic test to diagnose the condition” (David Robson). Synaesthesia which arises from non-genetic events, is referred to as “adventitious synaesthesia”, to distinguish it from the more common congenital forms. Adventitious synaesthesia, relating to drugs or stroke, (but not blindness or deafness), apparently only involves sensory links between sound, vision, and touch.

Physician Ross Quinn explains:
“As a physician (who is married to a synesthete), I too think there may be a connection to cerebral vaso-dilation and intensification of synesthesia. Any fever increases metabolism and blood flow generally, and Lola correctly describes the main stream explanation of migraine: an initial cerebral vaso-constriction, followed by over shoot with abnormal vaso-dilation / high blood flow. It seems logical to me that synesthesia would require more blood flow, as more parts of the brain become activated in synesthetes than in us “usual” people in response to every day stimulation. Any part of the brain that functions more requires more blood flow. Perhaps by increasing blood flow generally (e.g., fever, even anesthesia), or locally (e.g., migraine, or concussion, after which brain blood flow is often deranged), this could enhance, intensify, or even create temporarily new synesthesia. This speculation makes me wonder about another aspect of the psychedelics: They have seritonin receptor interactions, which are also involved in blood flow regulation.” (The Synaesthesia List, 2008).

One of the crucial effects of synaesthesia is that it reportedly improves memory and recall, (Cytowic 1995; Ward 2008), and synaesthetes appear to have exceptional photographic memory skills. For example: a synaesthete reading a book is more likely to remember a specific page number or place on a page of a particular event; likewise, a synaesthete who has become blind is more likely to visualize the layout of a familiar room. The synaesthetic experience gives additional associations for names, numbers, and sounds, which can provide a vivid link to the information, and the more forms of synaesthesia a person experiences, the better their memory and recall is likely to be, due to their additional sensory receptors being activated at any one time. Although this is currently an active area of research, an experimental study on people with dyslexia and who have grapheme colour synaesthesia showed, by associating letters with a particular colour assisted them in the reading and spelling of words considerably, as the colour progression through a word remained consistent, and appeared more memorable on the page than when asked to spell it verbally.

Synaesthete Liz Davies explains:
“I’m sure you will get some similar responses, but I think synaesthesia helped me learn to spell as a child – I always found it very easy to remember how to spell even difficult words, by the patterns the colours made. When a word was spelt wrong, I could immediately tell because a colour stood out, or ‘didn’t go’ with the rest of the word. I don’t know if I can still attribute it to synaesthesia as I tend to suppress the colours these days, but I could still spot a spelling error a mile off, which has earned me the additional role as proofreader at work!” (UKSA news letter, December 2007).

Many memory improving techniques recommended in self-help books use “artificial synaesthesia”, encouraging the individual to form vivid sensory associations with the information they wish to remember. For example: children’s alphabet shapes are represented by a different colour, in order to help the child make the association between the colour and the letter as a long term learning aid. For the genuine synaesthete, such techniques can simply form an encumbrance, cause confusion, and can even appear irritating – the Russian novelist Vladimir Nabokov, as a child, complained to his mother that the colours on his alphabet block were “all wrong”. Synaesthetes perform well in the superior range of the Wechsler Memory Scale (WMS, David Wechsler), whilst maths and spatial navigation abilities tend to suffer.

Synaesthesia continues to be investigated by scientists and neurologists worldwide, with particular reference to those in both the UK and USA. New aspects are being identified as the advances in modern technology reveal new techniques for deeper testing, including, and most recently, possible links between synaesthesia and emotion.