In this video I explain synesthesia, in which stimulation of one sense can automatically stimulate another, such as seeing colors when hearing pitches or tasting sounds. I also demonstrate one way that researchers can test certain types of synesthesia and describe how synaptic pruning is one proposed explanation for the occurrence of synesthesia.
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Recommended Videos:
TED-Ed – Richard Cytowic – Exploring Synesthesia
https://www.youtube.com/watch?v=rkRbebvoYqI
BBC – When Senses Collide
https://www.youtube.com/watch?v=rkRbebvoYqI
Video Transcript:
Hi, I’m Michael Corayer and this is Psych Exam Review.
In the last video I talked about this idea that our sense of taste is influenced by other senses so the things that you smell will influence your experience of taste and the things that you see can influence taste and even things that you hear.
So we have this idea that our senses are mixed together, there’s not clear separation between vision and hearing and touch. All of our senses kind of mingle together.
This is especially true for people with synesthesia. Synesthesia is a more dramatic mingling of the senses. It’s a situation where one sense automatically, involuntarily evokes another sense. So one way this could happen is if you have pitch-color synesthesia. This is a situation where somebody hears a particular pitch and they see a particular color. For instance if they hear an A they see red. If they hear an F# they see green.
Now, they’re not hallucinating, they know that they’re not actually seeing the color, but they have a vivid experience of color associated with each different pitch.
It’s also possible to have particular sounds stimulate tastes in some people. So they’ll describe a certain person’s name will automatically cause a certain taste in their mouth. It’s also possible to have synesthesia for certain shapes appearing colored. People will see certain letters as being particular colors. So As are always purple or Ps are always green. Something like that.
This is pretty interesting, the question we might have is “how do we go about testing this? How do we know that the person is really experiencing this vs. they’re just saying it?”. I could sit here and tell you that whenever I look at the letter D it appears blue and how are you going to find out if I’m telling the truth? Maybe I’m just saying that. You could test me, ask me again in a month what color I said Ds were and if I don’t say blue this time you’ll know that I was lying. But maybe I’ve just memorized it. For whatever reason I decided to sit down and memorize some colors associated with each of the letters. So how could you go about testing this?
One way that you could test it was developed by Vilyanur Ramachandran and Edward Hubbard. What they did was, they thought “if synesthetes can see particular letters as colored, in this particular type of synesthesia, then we could test them but giving them a bunch of letters to look at and see if they find patterns more quickly.” So let’s take a look at what this would be like. If we were to look at something like this and I ask you to find all of the Ps.
Now you can go through and look, “here’s a P, here’s a P” you can sort of gradually work your way through it. But the idea would be if somebody had synesthesia this task might be easier for them because the Ps are going to appear a different color. As soon as their eyes come across a P, let’s say they see it in yellow here, well then it’s going to immediately stand out. So the idea is that they would see this sort of triangle shape of Ps more quickly than somebody didn’t have synesthesia.
Ramachandran and Hubbard did find evidence for this. They found that people with synesthesia were slightly better at this task.
Again, people with this particular type of synesthesia. So if you had synesthesia for pitch and color, that wouldn’t apply to this situation. That’s one of the things that makes it kind of hard to do this research, you have to find people with this particular type of synesthesia. That’s going to be fairly hard to find, it’s a bit rare.
OK so that’s the general idea of how we test this. Now other people have done similar studies and the evidence is a little bit mixed and it might depend on the individual and just how vivid their synesthetic experience is. Some evidence has suggested that they’re not as fast as people looking at actual colored letters. So it’s not quite the same as seeing, if I were to show you this already colored in there you’d immediately see it, and the idea is that maybe synesthesia is a little bit slower than that, it’s not quite as immediate, but it still seems to have some advantage for this type of task.
OK, what’s causing synesthesia?
There’s one theory of synaptic pruning. Synaptic pruning refers to the idea that when we’re developing we grow lots and lots of neural connections that are later discarded. All sorts of neurons are connected to one another and then it’s sort of like “”use it or lose it”, right? If you don’t use those connections they disappear, they get pruned.
So one theory of synesthesia is that people with synesthesia, this pruning didn’t occur for certain connections that occurred normally for other people without synesthesia. So what happens is then stimulation of certain neurons automatically stimulates other neurons and this is why they have this experience. Somehow this area of cortex is sort of connected to this other area cortex automatically and that’s why stimulation of that area also stimulates the other area.
OK it’s kind of hard to really know what it’s like to experience synesthesia and I don’t have synesthesia so I can’t really describe it, I can only tell you what I’ve learned about it. But I’ll put a link in the video description where you can see some people talking about their synesthetic experience and hopefully this will give you a better idea of what it’s actually like to have synesthesia.
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Thanks for watching!
