Introduction

In this article, we are going to dive into the fascinating facts about the brain’s ability to interpret the surroundings and connect with the memories or senses. This ability to interact with two sensory pathways is known as synaesthesia.  This topic explores what synaesthesia can tell us about brain’s ability.

Do you have this amazing power to smell an old book placed on some shelf of an antiquarian library just by seeing a picture of it?

Or can you smell the fragrance of spring while reading William Wordsworth’s ‘Lines Written in Early Spring? 

or can you taste the delicious cookies just by thinking or hearing about the word Christmas? You might be experiencing a phenomenon called synaesthesia!

The word is rooted in Greek origins: “syn+aisthesis,” with syn meaning “together” and aesthesis meaning ‘sensation’ or ‘perception’.

Synaesthesia is a state of cross-action between two sensory pathways where stimulation in one pathway leads to the experience of sensation in another sensory pathway.

Types

In the last two decades of the nineteenth century, there was a rapid growth in the number of different varieties of synaesthesia and the number of new cases that were reported. 

As of now, there are numerous types of synaesthesia that exist, and the newly discovered synaesthesia is gradually adding up to the total of 80 discovered so far.

The majority of synaesthesia has been categorised into two major categories, Associative and Projective synaesthesia.

Associative synaesthesia

In this condition, individuals feel the relationship between the stimulus and the perception.

Projective synaesthesia

In this condition, the individual involuntarily experiences the perception of particulate stimuli, such as the projection of a guitar playing, as yellow in space, as if it imparts that colour around it.

The major types of synthesis that have been studied are as follows:

• Coloured Days of the Week

Associating the days of the week with colours, such as for a Synesthete Monday, is being projected as the dazzling yellow colour, not just the word Monday.

• Grapheme-colour synaesthesia

Associating letters and numbers with different colours, such as seeing the letter J as blue and the number 8 as brown,

• Chromesthesia

In chromesthesia or coloured hearing, an individual hears the sound of colours or sees them as shape, texture, or landscape. 

Ever seen a red or pink crayon singing a song? Well, a synesthete can experience a musical concert just by seeing a crayon.

• Ordinal linguistic personification

In this condition, synaesthesia manifests itself in a state where a person experiences numbers, days, multiple types of words, and objects as if they were real people.

Such as seeing Long Tower in a street as a politician or seeing the month of December as some muscular man.

• Mirror-touch synaesthesia

 Imagine if someone is pulling the handle to open the door and you feel like you are the one who is holding the door—that is what happened in this condition.

• Lexical-gustatory synaesthesia

If you can taste the word, this is the condition of lexical-gustatory, similar to it if you can taste the sound, this is the expression of sound-gustatory.

• Spatial Sequence Synaesthesia

Locating the series of numbers and months of the calendar at different positions as if they had the quality of location defines spatial sequence synaesthesia.

Conceptual Insight

Inducer and Concurrent Theory

Grossenbacher & Lovelace (2001) introduced the term “inducer” to describe the stimulus that elicits the synaesthesia and the term “concurrent” to denote the experience itself.

Thus, most of the types can be minimally described as an inducer-concurrent pairing. 

The inducer does not replace the concurrent, so someone having music-taste synesthesia continues to hear music as well as taste it. (Beeli et al. 2005). Here the music is the inducer while taste represents the concurrent stimulus.

Synaesthesia is distinguished from seemingly similar phenomena such as illusions (in which the inducer is, in some sense, misperceived) and hallucinations (a concurrent without an inducer).

• The most common synesthetic inducers are linguistic in nature: letters, digits, and words—particularly words that form part of a series (Simner et al. 2006). 
• The most common synesthetic experiences are visual in nature. This includes colour and coloured textures.
• The range of possible inducers and concurrence is very large, with new combinations still being discovered. This also leads to a puzzle as to what combinations of inducer and concurrent could reasonably be labelled as synaesthesia.

Synaesthesia as a disorder

If you have symptoms of synaesthesia, Wait, don’t be afraid; you are completely normal and healthy. 

It is not a disease or disorder, and research says experiencing this condition is a sign of intelligence. 

It has been linked to extraordinary cognitive talents and greater imaginative ability. Numerous studies have demonstrated that persons with this condition can perform better on particular memory and intelligence tests. 

So now you can certainly boast about being a “synesthete” (someone who experiences synaesthesia).

Thus, Individual synesthetes are not all psychologically ill. On tests for illnesses like schizophrenia, psychosis, delusions, and others, their results come back negative.

 Who has synaesthesia?

Those who experience this typically do so from birth or very early in life. It might evolve in the future. According to research, it can be passed genetically.

It is significant to observe that the loss of a limb can cause some synaesthesia. The phantom limb or phantom sensation is a consequence of the cortex being remapped after an amputation. Paresthesias is a better name for them. They vary from synaesthesia in that they can happen spontaneously and are not necessarily inherited.

Q&A

1. How many types of synaesthesia are there?

There are hundreds of types that exist.

The common types are depict associations between stimuli such as smell-colour, month-flavour, sound-emotion, sound-touch, day-colour, pain-colour, and personality-colour (auras).

2. When was synaesthesia discovered?

It was first observed in a case that was widely recognised as such in 1812. Georg Sachs, an Austrian physician, wrote about his and his sister’s albinism—a condition that both of them were afflicted by—for his medical dissertation. He provides specific examples of colours for numbers, letters, and other series as he explains his own synaesthesia in this thesis.

3. What percentage of the population has synaesthesia?

It is not exactly known, but previous studies about surveying synesthetes indicate that 3-4% of the average population might be experiencing this condition.

4. Can synaesthesia be diagnosed?

It is not something that can be clinically diagnosed, but there are many psychological assessment tests that can tell about the degree and range of association between two stimuli.

5. What is time-space synaesthesia?

Here experience a spatial perception of time. This means that the person may perceive time as having a spatial or geometric quality, such as seeing the months of the year arranged in a specific shape or seeing time as a physical path.

Written By: Deva Singh

References

• Ward, J. (2013). Synesthesia. Annual Review of Psychology, 64(1), 49–75. 
• Spector, F., & Maurer, D. (2013). Synesthesia: A new approach to understanding the development of perception. Psychology of Consciousness: Theory, Research, and Practice, 1(S), 108–129.