Synaesthesia (Greek syn – ‘together’ and aesthesis – ‘perception’) or ‘cross-sensory perception’ is an involuntary physical experience of a cross-modal association, i.e. the stimulation of one sensory modality triggers a perception in one or more different senses.

To translate it into plain English – if you answer ‘yes’ to one of the following questions you have synaesthesia:

• Can you see sounds?
• Can you smell colors?
• Can you taste shapes?
• Can you feel sounds on your skin?

Those with synaesthesia see sounds, or smell colours, or taste shapes, or feels sounds on the skin, or hear colours.

Synaesthesia is not homogenous and can manifest in different ways; in other words, there are different variations of synaesthesia. Many synaesthetes have more than one form of synaesthesia.

According to the number of senses involved, synaesthesia can be of two types:

• Two-sensory synaesthesia, when stimulation of one sensory modality triggers the perception in a second modality, in the absence of direct stimulation of this second modality. The examples of this type are:

• coloured-hearing: when a sound triggers the perception of a colour
• coloured-olfaction: when a smell triggers the perception of a colour
• coloured-tactility: when a touch triggers a colour
• coloured-gustation: when a taste triggers the perception of a colour
• tactile-hearing: when a sound triggers tactile sensation
• tactile-vision: when a sight triggers feeling shapes and textures pressing the skin
• tactile-gustation: when a taste is experienced as a shape
• audiomotor: when the sounds of different words trigger different postures or movements of the body etc.

• Multiple sensory (or multimodal) synaesthesia: when more than two senses are involved, e.g., when a child experiences the taste of the sound, while simultaneously seeing the colour and experiencing tickling sensation on the skin.

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Synaesthetic experience is very individual; for example, among people who see coloured sounds there is no specific colour for each sound from person to person.

More often synaesthesia is unidirectional, i.e. for example, sight may be experienced as touch but touch does not trigger visual perception.

Most people with synaesthesia do not complain of their condition because for them, it is their normal perception of the world and they are not aware of it causing any disadvantages. Moreover, they often enjoy it and think that losing their unique perception would be upsetting. Though it is true only if synaesthesia is unidirectional, whereas in case of ‘two-ways’ synaesthesia (when, for example, a synaesthete not only sees colours when he hears sounds, but also hears sounds whenever he sees colours) the individual really suffers from the condition – experiencing stress, dizziness, information overload, avoidance of noisy or colourful places, that lead to social withdrawal and interference with ordinary life. In some situations, when somebody says something, a child sees the word, but if more people are talking at the same room, blurs appear that break the word – making comprehension difficult.

Other types of synaesthesia involve letters, words and numbers: when letters/ words/ numbers are heard or read they are experienced as colours; or numbers are experienced as shapes or forms.

The research of prevalence shows that from two to five per cent of the population have synaesthesia. Synaesthesia appears equally in men and women. It is believed to be genetic.

Fifteen per cent of people with synaesthesia are reported to have a history of one of their first-degree relatives having dyslexia, autism or ADD. Learning disabilities seem more common in synaesthetes, however, the actual incidence of autism among synaesthetes is not known at present.

Synaesthesia is involuntary. It is a passive experience that happens to someone. Synaesthetic experiences are projected in the environment; they are not just in the head – they actually see sounds, hear colours, etc.

One of the most common features of synaesthetes is their superior memory (due to their parallel sensations). They remember conversations, verbal instructions and spatial location of objects in every detail. However, this phenomenal experience, though very useful in remembering things, could lead to complications. Their understanding of spoken or written speech is literal. Each word evokes images that distracts them from the meaning of the sentence as a whole.

Synaesthetes are observed to have uneven cognitive skills. They are reported to prefer order, neatness, symmetry and balance. Among their deficiencies the most commonly reported are right-left confusion (allochiria), poor math skills and a poor sense of direction.

Now we know that quite a few autistic individuals have synaesthesia as well. It is not easily detected because many autistic children with synaesthesia don’t realise that other people cannot, say, hear sounds while seeing colours. For them, it’s a normal way to perceive the world. Besides, even very articulate adults with autism find it hard to express their experiences because they are so different from the ‘norm’.

The first time I suspected this condition in some of my autistic students was when I brought coloured blocks with letters on them to the classroom. Suddenly Lena (7 years old at the time) grabbed one and threw it across the room: “The colour is wrong! “C” isn’t yellow, it’s brown!” With years, more followed. John displayed involuntary movements of the body in response to the sound of vacuum cleaners. Helen and Alex seemed to ‘see’ sounds. Alex even tried to describe this experience: ‘I was scared. I saw a yellow “z-z-z” sound’, ‘The eyes saw the wrong word’ (in response to a verbal instruction). When Alex was in a state of sensory overload his synaesthetic experiences aggravated his condition and could lead to ‘panic attacks’ and ‘aggression’. After one of these ‘incidents’ Alex tried to give his explanation of what had happened: ‘In the shop I heard black, then the word broke down into pieces and they entered my eyes. I became blind because everything was black.’ At the time I was bewildered with this explanation, and placed his ‘reports’ into the category ‘confusing’ (and accounted for Alex’s difficulty to describe verbally what he experienced). However, in 2011 I came across the account by Brian King, a social worker who is on the spectrum himself, as well as father of three autistic children. King explains that when he is listening to someone speak, he can see each word they say scroll through the air in front of him. If someone repeats a word in a conversation Brian sees it in a darker colour; and if his communicative partner emphasizes that word while speaking, it literally jumps out at him like 3D.

Though sometimes it can be overwhelming (in the case of bidirectional synaesthesia), in fact, synaesthesia is a unique way to perceive the world.

Written by Olga Bogdashina on behalf of Integrated Treatment Services