Have you ever wanted to know what sound the color green makes, what the word “computer” tastes like? Or perhaps you've wondered about the color and texture of the number 5?
Most people have probably never considered these issues and would dismiss these question as a bad joke. However for 2 to 4 percent of the world's population, these questions are relevant. Due to a neurological condition known as synesthesia, some people can provide insight into these questions.
Synesthesia: A Cross Activation of the Senses
Synesthesia was first scientifically recorded in 1812 by George T.L Sachs in a Latin-written treatise, which, when translated into English, may have been titled The Natural History of Two Albinos, the Author Himself and His Sister. Up until recently, the condition has received little interest and often been dismissed as a form of insanity.
There are approximately 60 different types of synesthesia, which are caused by an increased number of neural connections between sensory regions of the brain. As a result, a visual experience of sight may also evoke a taste. Alternatively, auditory stimulation may also trigger a visual experience of colors moving around a room. According to neuroscientists Vilayanur Ramachandran and Edward Hubbard, this condition may be caused by decreased neural pruning between regions that are interconnected in the fetus.
Studies have also found that 40 percent of people with the condition (known as “synesthetes”) have had a first-degree relative with synesthesia. According to neurologist, Richard Cytowic, having one variant of synethesia makes it 50 percent more likely that you too will experience a second or third form of this condition.
Cytowic also mentions that one in ninety people have lexical or grapheme-color synesthesia. In these cases, when the individual sees a written word, number, punctuation mark, etc., this induces an involuntary color experience. Cytowic says that scientists trying to find an alternative explanation than cross-activation between the senses, in the past suggested that synesthetes were "just remembering childhood associations from coloring books and refrigerator magnets, which is why 'A' is red or 'E' is yellow".
Some previous studies found that females were six times more likely to be synesthetes than males. However, more recent studies have suggested that these findings were influenced by methodological flaws and self-report biases. It's now believed that there is an even gender distribution among synesthetes.
Increasing Cognitive and Perceptual Abilities
A recent study on synesthesia by Ramachandran and David Brang, recently published in the journal PloS Biology, attempted to answer the question of why the condition has survived through evolution. They also sought to identify any evolutionary benefits associated with the condition.
The researchers found that synesthesia enhances the sensitivity of the individual's sensory systems, allowing synesthetes to perceive links in seemingly unrelated sensations and ideas. This leads to greater creative thinking.
The authors of the study argue that synesthetes may enjoy perceptual and cognitive benefits, such as increased detection, processing and retention of critical stimuli. An example of this is author Daniel Tammet who sees each positive integer up to 10,000 with its own unique shape, color, texture and feel. This allows him to demonstrate remarkable memory abilities by recalling pi up to 22,514 digits.
Grapheme-color synesthes tend to use color-associations to help them recall precise details, such as a phone number. According to the researchers they can also more easily discriminate between very similar colors and have a greater ability in the processing of color information in general.
A previous study found that people who feel sensations on their own body while watching someone else being touched, known as mirror-touch synesthetes, also possess greater tactile acuity. A 2008 study also found that hearing-motion synesthetes (people who experience sound when they perceive motion), could more easily recognize temporal rhythmic patterns by not only seeing the patterns (which took the form of visual flashes), but hearing the patterns as well.
Some scientists have suggested that synesthesia may be linked with savantism, which is where people with developmental disorders, such as autism, display incredible ability, expertise or brilliance in one or more areas at times.
Disadvantages to Synesthesia
David Brang told National Geographic that “ninety-five to ninety-nine percent of synesthetes love their synesthesia and say it enhances their lives”. However there are examples of disadvantages, such as synesthetes being ridiculed and mocked by non-synesthetes who are uninformed on the condition and consider synesthetic experiences to be related to insanity and drug use.
Number-color synesthetes have reportedly had some difficulty with simple arithmetic because they find the colors on the numbers "distracting". Some color synesthetes also claimed to perceive odd, disturbing and alien colors that only exist when they see graphemes such as numbers, colors and punctuation. Cytowic also mentions that other common problems experienced among synesthetes is getting their left and right confused and having a poor sense of direction.
Gustatory synesthetes have reported that specific words may evoke an unpleasant taste, such as earwax. In one extreme case, an audience member at a Richard Cytowic lecture told him that her synesthetic son had to be moved to another class after he complained that the taste of his teacher's voice made him feel sick.
Synesthesia Types
Based on 588 cases in 2006 (of which 40 percent of synesthetes had multiple types of synesthesia) the most common synesthetic connections involved color. These included:
- letters, punctuation and numbers appearing in different colors (68.8 percent);
- time units such as days, weeks and months being perceived as a particular color; (23.3 percent);
- the visual perception of color evoked by hearing music sounds (19.2 percent), general sound (14 percent), musical notes (10.6 percent) and phonemes (10.6 percent).
From these 588 cases synesthetic color was also triggered by:
- taste (7.1 percent);
- smell (6.9 percent);
- pain (6.3 percent);
- personalities (4.8 percent);
- touch (3.9 percent);
- temperatures (2.7 percent); and
- orgasms (1.1 percent)
Other common synesthesic connections included:
- sound to taste (5.6 percent);
- vision to taste (2.3 percent);
- sound to smell (1.6 percent);
- vision to smell (1.1 percent); and
- vision to touch (1.1 percent);
Another common type is spatial-sequence synesthesia where numbers, days of the week, months, years, etc. appear in visuo-spatial coordinates around ones body in a particular sequence, order or pattern (see Image 2 for an example).
Nobel physicist Richard Feyneman, was a well known spatial-sequence synesthete, who while teaching classes, perceived colored equations flying around him. A study performed by neuroscientist David Eagleman found that 49.3 percent of 1,067 grapheme-color synesthetes (seeing numbers, letters etc. in specific colors) also experienced spacial-sequencing.
The rarer types of synesthesia include the following.
- Ordinal linguistic personification -- Numbers or letters are perceived as having personalities and genders. Synesthete Megan Timberlake perceives the letter 'A' as a female who always wears a dress; 'D' is a a dashing male who is a bit of a joker. For Timlerlake, 'N' is a youthful and handsome male who is the meditative type and 'V' is an “unflauntingly sexy" and sophisticated female.
- Touch-emotion connection -- Ramachandran and Brang reported the first known cases of this form in 2008. One case involved a 22-year-old woman who experiences disgust of denim's texture, perfect happiness and contentment from silk. She experiences an electric shock from touching orange peels, whereas she feels jealousy when exposed to Tylenol gel capsules. A 20-year-old woman experienced a spine-crawling sensation while touching leather and she became irritated when touching bok choy. She experienced happiness while touching rigid plastic, sand and tennis balls.
- Audio-motor synesthesia -- There is just one known case of this form; it involves an adolescent boy who was discovered in 1966. In response to hearing certain English and nonsense words, the boy would feel compelled to make specific movements and strike various poses.
Artists with Synesthesia
Ramachandran and Brang note that synesthesia is seven times more likely to appear in artists, poets and novelists. Famous synesthetic artists include:
- Author Vladimir Nabokov, who saw letters in color;
- Actress and filmmaker Stephanie Morgenstern, who sees numbers and musical notes in color;
- Painter David Hockney who has synesthetic associations among sound, color and shape;
- Singer and actress, Stephanie Montreux who perceives words, letters and numbers in color;
- Composers such as Olivier Messaien, Nikolai Rimsky-Korsakov and Franz Liszt who all associated and perceived synesthetic colors with music;
- Musicians such as Stevie Wonder, Itzhak Perlman, Eddie van Halen and Billy Joel who also associate color with music;
- Actor Tilda Swinton who associates certain tastes (such as cake) with specific words (e.g table);
- Poet Charles Baudelaire, painter Wassily Kandinsky and composer Alexander Scriabin, whose work was inspired by synesthetic experiences but may not have had the condition themselves;
- Journalist, mnemonist and once hopeful violinist, Solomon Shereshevskii, who could forever recall his experiences in perfect detail and was incapable of forgetting information, by involuntarily transcribing sights and sounds into graphic images and synesthetic impressions of sight, touch and taste. Neuropsychologist A.R Luria claimed that Shereshevskii sensed "smooth, cold sounds and rough colors; salty shades and bright, clear or biting smells, all so intertwined that it was difficult to tell one sense from another".
Acquired Synesthesia
Synesthesia appears in up to 4 percent of the general population, but can also be induced by drug use, brain damage and sensory deprivation. Examples of the latter include cases when touch stimuli induce the visual perception of phosphenes (a phenemonon where an individual sees light, without light actually entering the eye) in people with retinitis pigmentosa, a genetic eye condition that results in partial or total blindness. Some arm amputees also experience sensations in phantom limbs when they observe someone else's body being touched.
A recent report in the neuropsychology journal, Neurocase, focused on a 45 year-old man who 9 months after suffering a hemorrhagic stroke acquired several variants of synesthesia, including sound-tactile (where sound induces the sensation of touch), sound-colour (where sound induces the visual perception of colour), and grapheme-gustatory (where words evoke the sensation of taste).
Past studies on synesthesia that was induced by hallucinogenic drugs also suggest that the gene responsible for this condition exists in the general public, but it may be suppressed in the majority of people.
Remaining Questions on Synesthesia
In their report, Ramachandran and Brang emphasize that there are still many unanswered questions concerning synesthesia. These include:
- whether the condition exists in animals;
- the connection between genetic synesthesia and those who have acquired synesthetic experiences through hallucinogenics, brain damage and sensory deprivation;
- whether the condition is unidirectional (e.g. sound can evoke the sensation of color but seeing color does not evoke the sensation of sound) or can be subconsciously bidirectional (e.g sound can evoke the sensation of color and vice-versa)
- whether the genes that predispose someone to synesthesia enhance these abilities independently and if family members of synesthetes, who are not synesthetic themselves but still carry the gene, experience the same perceptual benefits.
Sources:
- Brang D & Ramachandran V.S, “Survival of the Synesthesia Gene: Why Do People People Hear Colors and Taste Words”, PloS Biology. Volume 9, Issue 11, November 2011.
- Choi, Charles., “Why It Pays to Taste Words and Hear Colors”, LiveScience, 22/11/2011.
Cytowic, Richard., Wednesday is Indigo Blue: How Synesthesia Speak to Creativity. (AV Recording) USA, Library of Congress, 30/10/2009.
Cytowic R & Eagleman D., Wednesday is Indigo Blue: Discovering the Brain of Synesthesia. Massachusetts, USA; MIT, 2009. Chapter 2.
Ione, Amy & Tyler, Christopher., “Synesthesia: Is F-Sharp Colored Violet?” Journal of the History of Neurosciences, Volume.13., No.1, 2004
Luria, A.R The Mind of Mnemonist: A Little Book About a Vast Mind. USA; Basic Book Inc. 1968.
Ramachandran, V. S. and Brang, David 'Tactile-emotion synesthesia', Neurocase, Volume 14, No. 5, September 2008
Saenz, M & Koch, C “The Sound of Change: Visually Induced Auditory Synesthesia” Current Biology, Volume 18. Issue. 5. 2008.
Ward J & Cytowic R "Synesthesia and Language" in Harry Whitaker's (ed.) Concise Encyclopedia of Brain and Language. Oxford, England; Elsevier Ltd, 2010.
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