Have you ever tasted the color yellow? Or does your favorite poem evoke a distinctive smell? Then you, my friend, may have synesthesia. Synesthesia is an automatic linking of senses, where stimulation of one sense causes you to perceive another. Someone with sound-color synesthesia, for example, might hear their favorite song and think, “The greens and reds in that chorus, man! Let me tell ya…” It’s basically a weird brain superpower on its own.
And, turns out, people with synesthesia might even have a slightly better memory when it comes to certain things. About 2 to 4 percent of people have at least one subtype of synesthesia. Some might see colors in songs, while others taste numbers. Someone could even perceive time as a sort of spatial calendar that wraps around them. A synesthetic brain makes these associations between senses while you’re already using one of them. So it’s not the same as a hallucination, like hearing voices without any sort of stimulus. A 2011 review of the literature suggests that some people are genetically predisposed towards developing a subtype of synesthesia, thanks to the way their brains develop. The exact processes and brain areas responsible for synesthesia are still under debate, but we do know that synesthetic brains show more connectivity. Your brain has chunks of of gray matter, which is mostly neuron cell bodies and other brain cells, and white matter tracts, which are like the wire parts of neurons that carry information between more distant brain regions. Those white matter tracts tend to be more developed in synesthetes, especially between sensory areas.
Many researchers think this could be because of a failure in a developmental process called synaptic pruning. Synaptic pruning is pretty much what it sounds like. Imagine your brain taking a pair of gardening shears to the cell connections that are aren’t really needed to keep everything working. Typically, as you grow up, some white matter connections get pruned back and honed into certain paths.
Your brain is trying to optimize efficiency and get rid of connections that you don’t use to save energy. It’s possible that in synesthesia, this pruning doesn’t happen as effectively. This could leave all sorts of unexpected connections between brain cells intact. And as a result, the sensory regions of your brain may mingle with each other more than they should. Another hypothesis has to do with how your brain regulates when and how your neurons talk to each other. In people without synesthesia, when you perceive something with one sense, you just perceive that sense because neurons leading to other sensory regions are inhibited with some sort of chemical or physical barrier. And in synesthetic brains, those kinds of barriers might not function as well or in the same ways.
So certain kinds of stimulation might leak over into other sensory pathways, like activating smell which should have no business in perceiving the song you’re listening to. But all this talk of ‘failure of certain processes and systems’ almost makes it seem like synesthesia is an illness, but that’s not the case! Some people have even noticed that certain synesthetic associations can help them perform better on memory tests. In 2013, researchers conducted a memory experiment with a group of 28 color-letter synesthetes and 35 control subjects. First, they showed the participants a bunch of words, landscape pictures, and fractal patterns. Then, the researchers showed pairs of things the subjects had seen before and similar-looking words and images, and had people pick the one they recognize. Like, a pair of words would be: FISH and FIST. They found that the color-letter synesthetes were significantly better at remembering things in all of these categories than the control group.
However, when the same experiment was run with a group of 18 word-taste synesthetes and 18 control subjects, the data showed that the synesthetic people didn’t have a statistically significant advantage over the control group. Other small studies have had similarly mixed results. This makes it hard to tell whether just having synesthesia gives you memory boost because memory also has to do with making connections in the brain, or whether certain subtypes of synesthesia can help with certain tests. Some scientists think the memory advantage depends on whether the thing you’re trying to remember is going through similar sensory paths in your brain as your synesthesia. These researchers, for instance, concluded that the color-letter synesthetes likely had more activity in the visual brain regions, which could let them process and remember visual information—both images and words—better.
So if you find songs to be literally tasty jams, or think that the alphabet looks like a giant rainbow, you might have a bit of an edge on the rest of us when it comes to memory. Use your powers for good! Thanks for watching this episode of SciShow Psych, brought to you by our wonderful patrons on Patreon! If you’d like to support all the SciShow channels, you can go to patreon.com/scishow. And if you want to keep exploring weird brain things with us, go to youtube.com/scishowpsych and subscribe..