6. The question of synaesthesia

‘The question of synaesthesia’ looks at arguments against the Neonatal Synaesthesia Hypothesis and at other controversies and outstanding issues facing the field. It discusses the consistency-over-time feature and explains that although synaesthetes are highly consistent, they are not necessarily 100% consistent, and some synaesthetes might not be consistent at all. Is synaesthesia truly consistent over time as a definitional criterion, or does consistency over time merely characterize a subset of synaesthetes? There is also an imbalance between understanding the synaesthetes in English-speaking cultures and understanding synaesthetes worldwide, as well as between different types of synaesthesias. Despite the huge recent advances in understanding synaesthesia and how it affects synaesthetes, there is still more to learn.

4. Is synaesthesia a ‘gift’ or a ‘condition’?

Is there a consequence to having synaesthesia, even beyond the obvious difference of experiencing merged sensations? Do synaesthetes also have qualities that make them different to non-synaesthetes in other ways? Do they show differences in everyday abilities like memory, mental calculation, general perception, creative thinking, use-of-language and so on? ‘Is synaesthesia a “gift” or a “condition”?’ describes studies that show synaesthetes are objectively more creative than the average person, and have certain personality traits linked to heightened imagination. Synaesthetes also have specific visual benefits, such as the ability to better distinguish facial features and their expressions. Synaesthesia appears to come with a number of benefits, but it can also bring challenges.

3. Synaesthesia and the arts

‘Synaesthesia and the arts’ considers the link between synaesthesia, art, and creativity, discussing some key questions: is there an intrinsic beauty in the artwork created by synaesthetes that could make it inherently attractive to all people? Are synaesthetes able to tap into aesthetic beauty in some kind of privileged way? Are synaesthetes more creative than the average person, and do they engage more often in artistic pursuits? It discusses the diagnostic test for synaesthesia and why it is that some people incorrectly claim to have synaesthesia and why others do not report it. Having synaesthesia does bring a creative streak to the personality, and synaesthetes are significantly more likely to follow artistic careers than the average person.

1. What is synaesthesia?

Synaesthesia manifests in many different ways, and this poses a challenge in setting out a definition. ‘What is synaesthesia?’ explains that the triggers (inducers) and the resulting unusual associated sensations (concurrents) can be all manner of sensations, or even intangible concepts of personality, meaning, space, and time. It describes several different types of synaesthesia, including sound–colour, lexical–gustatory, visual–auditory, sequence–space, grapheme–colour, and sequence–personality synaesthesia. The number of people with synaesthesia make up around 4.4% of the population and it appears to affect men and women in equal numbers. Despite being a rare condition, synaesthesia provides intriguing information about how the mind interprets reality and how information is organised by the brain.

5. Where does synaesthesia come from?

Why are the brains of synaesthetes so ‘communicative’ and how exactly do synaesthetic sensations form? ‘Where does synaesthesia come from? The role of genetics and learning’ asks whether synaesthesia is pre-determined in the genes, or based on learning from the environment by considering synaesthetic associations, synaptic pruning, and the Neonatal Synaesthesia Hypothesis. It shows that synaesthesia emerges over time, that it can follow rules based on information absorbed from the environment with these rules sometimes shared by non-synaesthetes, and that synaesthesia has a likely genetic inheritance. It concludes that synaesthesia derives not only from post-birth events such as literacy acquisition and environmental submersion, but is also likely to be predetermined in some way at birth.

2. Synaesthesia in the brain

Advances in brain imaging have revolutionised the study of synaesthesia and have enormous potential in educating us about the aetiology of this unusual condition. Brain scans provide clear and irrefutable evidence of how synaesthetic sensations are grounded in the brain. ‘Synaesthesia in the brain’ describes several seminal studies in the brain imaging of synaesthesia, which have involved a mixture of techniques: positron emission tomography, functional magnetic resonance imaging, and diffusion tensor imaging. Two key questions have been considered: do synaesthetes have functional or structural differences in their brains, and are their direct or indirect connections between the different parts of the brains that are triggered by different senses?