Synesthesia is the fascinating neurological phenomenon whereby stimulation of one sense involuntarily triggers another sensory pathway. A synesthete might taste sounds or hear colors. Now, leading synesthesia researcher VS Rakmachandran at the University of California, San Diego is studying "calendar synesthetes" who see very clear images of calendars in their mind's eye when they think about months that have passed or are in the future. For example, according to New Scientist, one participant in the research "sees her months as occupying an asymmetrical “V” shape. Along this V, she sees each month written in Helvetica font." From New Scientist:
The idea that calendars are literally laid out in space for some people suggests that we are all hardwired to some extent to map time in space.
The concepts of time and numbers are something we acquired relatively recently in our evolutionary history, says Ramachandran, but the brain wouldn’t have had time to evolve a specific area to deal with it.
“Given the opportunistic nature of evolution, perhaps the most convenient way to represent the abstract idea of sequences of numbers and time might have been to map them onto a preexisting map of visual space, already present in the brain,” he says.
Indeed, imaging scans show connections between areas of the brain involved in numbers and those involved with mapping the world, memories and our sense of self. The team suggest that when these areas act together, they enable us to navigate mentally through space and time, while being firmly anchored in the present.
Ramachandran suggests that for calendar synaesthetes, altered groups of genes may prevent pruning of connections between these areas during development, making the more abstract concept of a calendar mapped in space, for some, a real perception.