Does synaesthesia protect against age-related memory loss?

Synaesthesia is known to be linked to enhanced episodic memory abilities, across a variety of stimuli and tests, but the evidence has tended to come from younger adults. This enhanced cognitive ability in early adult life, together with the known brain-related differences linked to synaesthesia (e.g., in both grey and white matter structure), makes it an ideal candidate for exploring the notion of 'reserve'. That is, synaesthetes may be able to utilize additional cognitive and/or neural resources to mitigate against the effects of age-related decline. This was explored in a 2 × 2 design contrasting age (young, old) against the presence/absence of synaesthesia in two different studies: recognition memory for digits, snowflakes, and music; and visual associative learning. Synaesthesia and age had independent, non-interacting, effects on memory ability suggesting that, while synaesthetes show a memory advantage and maintain this advantage in later life, the presence of synaesthesia is not able to act as a reserve to protect against the effects of ageing. On our tasks, the benefit of having synaesthesia (enhancing memory) was of a similar magnitude to the effects of age (impairing memory); in other words, elderly synaesthetes present with 'youthful' memory abilities. It is important for future research on elderly cohorts to consider the presence of synaesthesia as an individual difference.