One of the most important facts to understand about synesthesia is this: it is not a disease, it is not an illness, and it is not a condition. According to Dr. Richard Cytowic, MD, a leading researcher on synesthesia, joined senses are best described as a trait, similar to having curly hair, or brown eyes. Current research points to a genetic basis for synesthesia; it tends to run in families, although it’s possible that not every member of a family will have the same types of synesthesia. One family member might see colors when they hear music, another might experience flavors in words, while others in the family might not have any synesthesias.
Interestingly, synesthesia seems to confer some benefits upon those who have the trait. For example, people with grapheme->color synesthesia, meaning the person sees their letters and numbers in color, tend to have stronger memories than average. In a recent paper titled “A persistent memory advantage is specific to grapheme-colour synaesthesia” by Katrin Lunke and Beat Meier of the Institute of Psychology, University of Bern, Bern, Switzerland, the researchers showed that “synaesthesia is associated with a memory advantage”. The results of their study imply that a benefit through enhanced colour-processing is particularly strong and that synaesthesia can lead to a long-lasting memory benefit.