The science of illusions, and what they tell us about how our brain senses our world
Every day you see things that aren't there- and that's a good thing.
The world is not as it seems — and not just because of COVID.
Your brain is continually playing around with your sense of reality.
But you may only notice this when you get caught out by a magic trick, a blue-and-black striped (or is that a white-and-gold striped) dress, or an enormous moon rising above the horizon.
Illusions have been used throughout history to amaze, entertain, trick and even scare us.
But they are also a mind-boggling window into how our brain works.
"Illusions help us understand the rules our brain uses to create reality, based on the input it receives from our senses," says Mark Williams, an honorary professor of cognitive science at Macquarie University.
"What we actually see or hear or feel or taste or smell isn't actually what's out there, but what we think is out there.
"Because we don't see the world as it actually is, illusions explain to us how we are creating the world we actually perceive."
We tend to separate what we think of as "the real world" and "illusions", says Branka Spehar, a psychologist at UNSW, who studies visual perception and attention.
"On some level, everything is an illusion and nothing is an illusion."
Our brain does not sense the world in absolutes; instead, it compares the sum of all parts of what it perceives and filters out information it doesn't think is important.
"Our sensory systems respond to the sum of all the contextual information in which the relative information is more important than the absolute," Dr Spehar says.
"So for example, you perceive colour relative to the background, or you see orientation relative to the frame of reference."
And with so much going on, sometimes we can overlook the simplest of details. [continues]