Article reviewed on 08 January 2026

Imagine tasting a sound or feeling the texture of a melody on your skin. For some people, this is not fantasy – it’s reality. This fascinating phenomenon is called synaesthesia or ‘cross-sensory perception’, in which a sensation in one sensory modality triggers a perception in one or more different senses: synaesthetes can see sounds, smell colours, taste shapes, feel sounds on the skin etc. Some people may forget the name of the person they know but remember the colour, taste or even temperature of the word.

Different forms of synaesthesia

There are different types, variations and forms of synaesthesia. Two broad categories include sensory synaesthesia and cognitive or conceptual synaesthesia.

Sensory synaesthesia

Depending on the number of senses involved, sensory synaesthesia can be of two types: 

Two-sensory synaesthesia – when stimulation of one sense triggers the perception in a second sense. For example, someone may complain about the sour taste of the somebody’s voice. 

There can be many different combinations of senses, such as:

• 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.

multi-sensory synaesthesia – when more than two senses are involved. This type of synaesthesia is when it gets really complicated. For example, a child may experience the taste of the sound, while simultaneously seeing the colour and experiencing a tickling sensation on the skin.

Cognitive and conceptual synaesthesia

Cognitive synaesthesia combines sensory (usually colour) and semantic triggers – when letters/words/numbers are heard or read, they are experienced as colours or tastes. For example, the word ‘Monday’ might always look purple.

A variant of the cognitive synaesthesia is a conceptual synaesthesia: when abstract concepts (for example, units of time, mathematical operations) are perceived as shapes or colours (Carpenter, 2001). For instance, when an arithmetic problem was presented: 5+2, the answer was ‘yellow’ (for 7) (Dixon et al, 2000). 

Sometimes numbers are experienced as shapes or forms. In the fascinating book Born on a Blue Day, Daniel Tammet, who is autistic and has synaesthesia, describes experiencing numbers as cities which he can walk through.

There are other phenomena that some researchers consider as variants of synaesthesia, for example, pain synaesthesia: when pain is felt in colour or when negative emotions of your communicative partner have metallic taste on your tongue.

Some synaesthetes have only one form of synaesthesia, while others have several forms or variants of it. 

Prevalence and links to autism

Synaesthesia occurs in the general population, but studies show it’s much more common in autistic individuals. Baron-Cohen et al (2013) found that 18.9% of autistic adults report synaesthetic experiences compared to 7.2% of non-autistic adults. 

Genetic studies indicate a shared predisposition between autism and synaesthesia (Nugent and Ward, 2022; Neufeld et al, 2025); both share features, such as sensory sensitivity, detail-focused processing and a predominance of local over global connectivity in the brain (van Leeuwen et al, 2019; 2020). When autism and synaesthesia co-occur, cognitive and memory strengths may be amplified, but so can sensory overload and stress. 

General features of synaesthesia

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

There are some general features of synaesthesia, suggested by Richard Cytowic (2002):

• Synaesthesia is involuntary – it is a passive experience that happens to someone. The sensations cannot be suppressed or incurred. 
• Synaesthesia is projected into the environment – it is not just in the head, but the individual actually sees a sound, hears a sight etc.
• Synaesthetic perceptions are durable and generic – in other words, they do not change over time or situation, and they are always experienced with the stimulus.
• Synaesthesia is memorable – the synaesthetic sensations are remembered best.
• Synaesthesia is emotional – having this experience causes pleasure.

A unique cognitive style

Synaesthetes typically exhibit preference for order, symmetry, detail-oriented thinking, vivid mental imagery, excellent episodic memory and heightened attention to detail. Those with multiple synaesthetic forms often display the most distinctive cognitive styles (Ward and Filiz, 2020).

Seeing sounds, words, and numbers in colours or feeling them as textures can help people to remember information. Often these secondary perceptions are much more vivid and vibrant than the primary ones, so they provide additional cues to retrieve the information from memory. The combination of a sensory imagery and a verbal thinking style provide original ways to solve problems.

Synaesthesia is associated with a vivid imagery cognitive style. Graphemes involve serial, analytic processing (a verbal cognitive style), whereas colours are visual and involve parallel holistic processing (a visual cognitive style). The combination of a verbal and a vivid imagery visual styles and their ability to switch easily between the two may be the core of the cognitive benefits related to grapheme-colour synaesthesia (Meier and Rothen, 2013).

Synaesthetes are observed to have uneven cognitive skills. They prefer order, neatness, symmetry and balance. They are more prone to unusual experiences such as déjà vu, clairvoyance etc. Among their problems, the most commonly reported are right-left confusion (allochiria) and a poor sense of direction. 

Strengths and Challenges

For many, synaesthesia is not a problem – it’s their normal. In fact, most wouldn’t want to lose it. Many synaesthetes report that their experiences add beauty and meaning to life:

But there can be challenges: 

• Sensory overload

More often synaesthesia is unidirectional, eg sight may be experienced as touch, but touch doesn’t trigger visual perceptions. However, when synaesthesia is ‘two-ways’ (eg a person with synaesthesia not only sees colours when they hear sounds, but also hears sounds whenever they see colours), the individual can really struggle. They can experience stress, dizziness and information overload. Because of this, they may avoid noisy or colourful places and may withdraw completely. As autism comes with other sensory differences as well, it becomes harder to deal with sensory overload. 

• Communication difficulties

A person can experience problems communicating with others because the voice hurts or sends flashes of colour that disrupts the understanding. Or a voice may be so pleasant (with pleasurable sensory experiences – colour, movement etc.) and fascinating, that the person cannot focus on the conversation and lose the meaning of verbal utterances.

In some situations, when somebody speaks, a child might see the word, but if more people are talking in the same room, blurs appear that break the word, making comprehension difficult.

• Literal interpretation – images triggered by words can make understanding abstract language harder.

People can remember conversations, verbal instructions, movie dialogues, text blocks in books, precise location of objects, furniture arrangements etc in every detail. However, this phenomenal experience, though very useful in remembering things, can 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. 

Professional experience

One of my first experiences of synaesthesia in autistic people was during my teaching days at a school for autistic children. I brought some coloured alphabet blocks into the classroom for fun learning. But seven-year-old Lena definitely didn’t think this idea was much fun. She grabbed a block and threw it across the room:

At the time, I was bewildered with his explanation and placed his reports into the category ‘confusing’. However, in 2011, I came across the account by Brian King, a social worker who is autistic himself. King says that when he is listening to someone speak, he can see each word – words 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 emphasises that word while speaking, it literally jumps out at him like 3D. Thus, Alex sees not only colours in response to sounds, but also words (yes, words) when he hears them. 

Listening to the child

Children’s experiences of synaesthesia are very real. Listen to your child, don’t dismiss their attempts to explain what they experience. Many won’t talk about it either because they are not aware that their experiences are different from those around them, they don’t want to be considered ‘mad’/’psychic’, they have communication challenges (inability/difficulty to express themselves) or they speak few or no words at all. 

Yes, sometimes there are challenges, but the synaesthetic experience of each autistic person with synaesthesia is a unique (and valid) way to perceive the world they live in. While it’s puzzling for many others, they must be puzzled too – why can’t people see the range of colours in a noisy environment or the words floating between us?