Synaesthesia Discovery

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Smelling Sounds and Hearing Smells: an Introduction of Bidirectional Synaesthesia


Bi-directional synaesthesia means that synaesthesia can be perceived in both directions, e.g., grapheme -> colour and colour -> grapheme. The term “bi-directionality” was only introduced a few years ago as synaesthesia was previously viewed as unidirectional.

There is no doubt that bi-directional synaesthesia is much rarer than unidirectional synaesthesia. Last month, I ran a series of sound synaesthesia in which sounds acted as a concurrent, i.e., the additional sensory experience. This time, I will walk through another set of sound related synaesthesia types in which sounds play a role as an inducer.

Through these two sets of blogs, I hope to expand the concept of bi-directional synaesthesia and spark some new interest in synaesthesia research as I think bi-directional synaesthesia is undoubtably a remarkable phenomenon.

You may recall a few stories in one of my previous blogs about Thomas’ smell -> sound synaesthesia ( The smell of honey makes Thomas hear bees. Going another direction, the noise of bees makes him smell jam. Honey and jam are two common toast spreads that he has for his breakfast.

His synaesthesia of smelling Indian curry giving rise to the sound of a spice mixer also goes the other way. The noise of a spice mixer triggers off the aroma of Indian curry.

Thomas’ sound to smell synaesthesia is as strong as his smell to sound whereas Skye only has unidirectional smell to sound synaesthesia. However, Skye has many other bi-directional synaesthesia, some can be extremely rare and almost have a domino effect. For example, we were eating a Mexican meal last weekend. The taste of the Mexican food triggered off the sound of people cheering which further triggered off a vision of a red curtain. The synaesthesia then travelled the other way. The red curtain made him hear people cheering, and the sound of people cheering elicited a flavour of rice.

One of the enjoyments I get from learning my children’s synaesthesia is those metaphors which are both fascinating and amusing. Thomas’ sound -> smell is no exception. After the success of his first poem, he wrote another one for this blog:

When I hear people kicking the footy I smell onion
When I hear peoples tummy rumbling I hear people eating
When I hear dinosaurs roaring I smell dust
When I hear people stomping I smell carrots
When I hear people yawning I smell burps.

Thomas is a very gentle and affectionate boy. He loves kissing me. When he smells Mummy (me), he hears people kissing. When he hears people kissing, he hears a very quiet whisper of ‘Mummy’. This is not quiet a bi-directional synaesthesia, but is actually another revolutionary discovery of my children’s synaesthesia, i.e., sound -> sound. In another word, they experience the same sensory as both inducer and concurrent. This can even start challenging the definition of synaesthesia.

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