In my previous blog post, https://sites.psu.edu/pscyh256su15/2015/06/14/eidetic-synaesthesia/, I talked about the experience of synaesthesia, a condition where the sensory areas of the brain are cross-wired. The difficulty of explaining this condition to other people is that the most common question is whether I physically see the images in question or whether they’re ‘just in my head’. The truth is that the images are mental ones, but mental images I have no control over.
One example is that the same piece of music will consistently produce the same mental imagery for me. Chopin’s Berceuse is always the exact shimmery silver-blue with ripples like raindrops falling on it, though each different recording by a different pianist changes the precise ripple effect. My spouse’s voice is never anything other than crimson silk velvet, despite the exact shade of crimson varying based on tone, mood, and other factors. The letter A is always red, no matter where it’s located in a word, and the letter E is a robin’s egg blue. The imagery created by my synaesthesia is highly consistent, on the same level as actual sensory perception, and current theories state that synaesthesia creates that actual sensory perception in other areas from a single stimulus that would usually be perceived by only one sense.
There is a difference between normal mental imagery and synaesthesia. Where mental imagery for most people is entirely voluntary, such as re-creating a room to remember where they left a book, synaesthesia is an involuntary sensory experience triggered by one stimulus perceived by one sense, and setting off other senses in combination. The consistency of the resulting imagery marks it as different from other kinds of mental imagery, which leads to it being categorised as a separate sensory perception despite the imagery being mental. For example, the colours that I ‘see’ that are caused by sounds are mental rather than with the eye: like having a flashlight with different coloured slides in my brain, not like having a pair of glasses with lens colours that change based on sounds.
The imagery of synaesthesia takes the same pathways and activates the same areas in the brain as mental imagery, but has been found to have similarly-heightened activity in the rear areas of the brain to perception. In addition, the sensation of synaesthesia as opposed to mental imagery can be differentiated for synaesthetes, as mental imagery only usually incorporates visual images and synaesthesia is multi-sensory. There are synaesthetes who have reported tastes with sounds, for example, and one variant of synaesthesia known as ordinal-lingual personality is when letters and/or numbers have personalities. A friend of mine has this variation and has reported that when she had to learn her multiplication tables, the number 8 had such an unpleasant personality to her that she had to change the way she learned the 8s, turning 7 x 8 into 7 x 7 + 7, or the negative association with 8 would have been too overpowering for her to actually learn the required multiplication tables. I had a similar experience myself with the key of C-major in music, having to transpose pieces in that key to another that had a less unpleasant image. The association of positive and negative traits with synaesthesia imagery also points to top-down processing, given that emotions are involved.
Synaesthesia is both predictable and unpredictable for synaesthetes as we know what our sensory experiences will be with familiar stimuli, but new situations and stimuli can be overwhelming. A synaesthete’s brain is constantly on sensory overload and this can be draining, not to mention that the experience intensifies when under the influence of alcohol or pain medications, and synaesthetes who experience neurological conditions like migraines and seizures often find that these conditions are more severe. Despite this, synaesthesia makes the world a bit more of a beautiful place and creates an almost-magical way to see the world.
Goldstein, E. Bruce. (2011). Cognitive Psychology: Connecting Mind, Research, and Everyday Experience. Belmont, CA: Wadsworth.
http://www.daysyn.com/Definition.html
http://www.sciencedirect.com/science/article/pii/S0010027713001212
http://link.springer.com/chapter/10.1007%2F978-1-4614-5879-1_10