The brain sure is a tricky part of our body, often playing games with what we think we see or hear! Sometimes, what we perceive and what’s actually there can be quite different – we call these moments “illusions”. Illusions aren’t just limited to what we see, like optical illusions, but also what we hear, called auditory illusions. And there are so many different types of optical illusions, categorising them can get pretty tricky, especially since we don’t always understand why they happen.
But these illusions are not just mind-benders; they serve a greater purpose. Did you know they can actually be helpful in understanding how our minds work and even in diagnosing psychological conditions? Sometimes, the tricks our brains play are actually signs that everything is working just right!
Hollow-Face mask
The hollow-face illusion was first shared with the public by Richard Gregory in 1973. It’s a great example of how our brains can see things in a surprising way!
Gif: rotating hollow face mask
Gif credits: cracked.tumblr.com
What exactly are the hollow face mask illusions?
Imagine you are looking at a mask. It’s hollow, but your eyes and brain trick you into seeing it as a forward-facing face – this is called the hollow-face illusion. Scientists have been curious about why our brains do this, even when we know the mask is hollow, and how this illusion affects the way we interact with the world.
Some researchers found that when people are asked to judge distances on such illusory faces, they still act as if the face is pointing outwards, though the illusion is not as strong due to some depth clues our eyes provide.
Image: position of observation and what our brain sees
Image credits: brainfacts.org
Schizophrenia and hollow face mask illusion
Researchers were curious about why people with schizophrenia—a condition that can cause hallucinations and a disconnection from reality—weren’t tricked by this illusion. So, they conducted a study with people who have schizophrenia and people who don’t, using a special scanner to see how their brains were working while they looked at these tricky masks.
What they found was pretty interesting! In people without schizophrenia, the brain made stronger connections between the area that processes what we see and the area that deals with expectations, making them see a regular face instead of a hollow one. However, in people with schizophrenia, this didn’t happen, so they saw the mask as it really was—hollow!
A fun fact: it’s not just people with schizophrenia who can see through this illusion. People who are drunk or have taken certain drugs can also “beat” the illusion, seeing the hollow face correctly! The scientists think this might be because, like in schizophrenia, there’s a disconnect between what the brain expects to see and what the eyes are actually looking at.
After exploring the mysteries of the Hollow-Face illusion, let’s delve into another fascinating phenomenon – the Rubber Hand Illusion.
Rubber hand illusion (RHI)
Ehrsson, Spence, and Passingham (2004) did studies on the “rubber hand illusion”, originally reported by Botvinick and Cohen in 1998.
Gif: Person perceiving the rubber hand as his own!
Gif credits: tumblr.forgifs.com
What is the rubber hand illusion?
Imagine you’re watching a rubber hand being stroked at the same time as your own hidden hand. This experiment is called the Rubber Hand Illusion. It’s this quirky trick where you might start feeling like the rubber hand is actually your own! This happens especially when both hands are being stroked at the same time.
Scientists call the feeling of the rubber hand being yours a “feeling of ownership”, and they’ve noticed that if the stroking isn’t in sync, people don’t really feel like the rubber hand is theirs. They’ve also found out that people’s sense of where their real hand is can shift towards the rubber hand – this is called “proprioceptive drift”.
Let’s explore how our brain plays tricks here!
So, why does this happen? Researchers think it’s a mix of what you see, what you feel, and your awareness of where your body parts are. When these things match up, your brain gets convinced that the rubber hand is part of your body!
Now, these smart scientists did more experiments to understand this better. They looked at how people’s sense of hand location changed over time, and they found some pretty interesting stuff. Even if the stroking wasn’t in sync, people still experienced a shift in where they felt their real hand was! But, this shift was smaller compared to when the stroking was in sync.
Here’s the kicker, they realised that this shifting feeling and the feeling of ownership might be happening because of different brain processes. It seems like when the stroking is in sync for a long time, people feel the shift more, but this shift can still happen without any stroking. But, if the stroking isn’t in sync for a long time, it messes with how our brain matches up what we see and feel, so we are less tricked by the illusion!
Understanding the workings of this illusion is not just intellectually stimulating; it has significant practical implications, particularly in the field of rehabilitation.
RHI is a rehabilitation tool!
Scientists have been super curious about this. They’ve mostly been looking at what’s going on in the brain when this happens and how they can make someone experience this illusion. But here’s where it gets even more interesting – this rubber hand trick has practical applications. It could actually help people who have lost a limb feel like a prosthetic limb is really part of their body!
Plus, by using special equipment like cortical electrodes (think of them as little gadgets that help us peek into the brain), researchers could learn even more about how our brains make us feel ownership of our body parts. This means the Rubber Hand Illusion isn’t just a neat party trick – it could be a game-changer in helping people recover and feel whole again, and that’s big news for doctors and folks working in rehabilitation!
While this illusion is widespread, there are some exceptions. Here’s an interesting observation!
Fun fact! Here’s an intriguing tidbit for you! Not everyone falls for the Rubber Hand Illusion, especially dancers and musicians. They seem to have a knack for it! Dr. Ehrsson theorises that individuals in these professions possess an exceptional ability to accurately locate their limbs without needing to see them.
These are just a few of how the illusions are not just fun but also a tool to understand how our brains work. The illusions find their place not just in fun, and health but also in magic shows, art, architecture, etc. We hope you found this exploration of illusions both enlightening and enjoyable.
Stay tuned for more science, fun, and facts!
Reference:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433454/#:~:text=Although%20there%20are%20many%2C%20sometimes,1%5D%E2%80%93%5B3%5D.
- https://www.wired.com/2009/04/schizoillusion/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125296/
- https://pubmed.ncbi.nlm.nih.gov/22000838/
- https://arstechnica.com/science/2020/01/study-finds-that-the-popular-rubber-hand-illusion-could-be-used-to-treat-ocd/#:~:text=But%20not%20everybody%20is%20susceptible,localize%20their%20limbs%20without%20sight.%22