People with synesthesia are usually born with it or it’ll develop in early childhood. Research suggests that synesthesia is often hereditary.
Synesthesia is caused by a merging of senses. For example, both the primary visual cortex and parietal lobe may be stimulated when looking at a colour. As a result, the person may be able to ‘taste’ the colour they’re looking at as the parietal lobe is also stimulated, which tells an individual what something tastes like.
In extremely rare cases, some individuals might develop synesthesia later in life, but this isn’t common.
See Also
The Happiest Color – Dorn Color