Week 9 reading- “Reality” is constructed by your brain. Here’s what that means, and why it matters. Flashcards
What can visual illusions teach us?
-Experience of reality is not perfect
-Teach us about the nature of our consciousness
How does our brain result in optic illusions?
Most of the time, the story our brains generate matches the real, physical world — but not always. Our brains also unconsciously bend our perception of reality to meet our desires or expectations. And they fill in gaps using our past experiences.
=bias us
How can understanding optic illusions deepen our empathy/ understanding of other people’s perceptions?
-Our perceptions are not a perfect mirror of the external world
-Neither are other peoples
-By understanding where perception can go wrong (‘our blind spots’) we can learn to understand how different people’s views may arise even if we do not agree with them
Double drift illusion
-What is presented at the start of the article
-look at a black dot on the left of the screen, in right of screen (periphery) is a fuzzy striped kind of dot thing
-This ‘striped dot’ appears to be moving diagonally however it is actually straight up and down (as demonstrated when you trace it with a finger)
-Importantly, even when you know what is happening you can’t consciously override the ‘wrong’ interpretation i.e. you still see the illusion.
Cavanagh at colleagues double drift illusion fMRI study?
-Ran a neuroimaging study that compared how the brain processes the illusory animation (double drift) with a non-illusory animation (the object/ striped dot thing is actually moving diagonally)
-Why do we see both similarly? What is the source of the illusion? Where does conscious perception diverge from physical sensation?
-9 participants, each participant did experiment 10 times
-The two animations produce different patterns of activation in the visual cortex: the visual system ‘thinks’ they are different so why do we perceive them as the same?
-Pattern of activation in frontal lobes are similar for the two animations= this is the source of the illusion- higher levels of processing overriding the visual system.
What does the fact that we can’t override the ‘wrong interpretation’ in the double illusion tell us?
That the stories our brains tell us about reality are extremely compelling even when they are wrong.
How much does our visual system run behind the real world? Why?
-100 milliseconds
-This is because we don’t have the necessary machinery (and wouldn’t want to) process all the information we are constantly bombarded with
-It takes time for light to hit the retina at the back of the eyeball, be converted to the retina and travel via the visual processing system to the cortex
What is required because of the fact that our visual system is delayed?
-We cannot rely on soley outdated information: we would be less coordinated and possibly get hurt more open
-To overcome this the brain predicts the path of motion before it happens: this ‘story’ becomes our reality and likely what is happening in the double drift illusion
Flash-lag-illusion
-The red dot is moving across the screen, and the green dot flashes exactly when the red dot and green dot are in perfect vertical alignment.
-It’s very hard to see the red dot and green dot as perfectly aligned: instead we perceive the red dot as being a little father ahead as we predict the path of motion for the red dot
If prediction is the primary way we experience consciousness- what does real time sensory information serve to do?
Acts as error correction: course correction when our predictions go wrong
Is prediction used only for the experience of motion?
-No, used for other aspects of consciousness too- such as colour perception
-Colour illusion by Akiyoshi Kitaoka: Square moves across screen with a different colour background. As moves the square appears to change colour but it actually remains the same colour the whole time!
-Shows us that colour is experience via inference: we use surrounding color cues and assumptions about lighting to guess an objects true colour but sometimes these guesses are wrong e.g. the dress (blue/black or white/gold)
Difference between those who see the dress as blue/ black or white/ gold (Wallisch)
-Built on earlier work by Rosa Lafer-Sousa
-People make different assumptions about the light that the dress is under and this effects their colour judgement of the dress itself
-Life experience is proposed to influence perception of the dress: early rises said to see it white/ gold, night owls more likely to see it as blue/black (study of 3000 people)
-Early risers assume that the dress is being bathed in sunlight (as this is how they see the world most) and so attribute a blue tinge to that as opposed to the dress itself. Therefore, see white/ gold
-Night owls assume dress is under artificial lighting and filtering that out makes the dress appear blue/ black
To sum: brain fills in ambiguity of the lighting based on what is most familiar to us (also seen in other viral illusions such as Yanny and Laurel)
Does Wallisch lark (early riser) versus night owl theory fully explain the dress illusion?
- Still lots of other things that could be influencing dress perception
-Prior experience with the subject matter, or related to other aspects of people’s personality?
-Extended the dress by creating new images (crocs and high socks) which people see as green or pink
Kanizsa triangle + patient MM
-Pac man like shape gives shape the impression of a triangle in our minds
-We only need a suggestion to fill in the shape with our minds
-Experience/ life time of seeing triangles is influencing this illusion as patient MM who lost vision at age 3 and had it surgically restored years later (in 40s) can’t see it. Doesn’t have the information to base predictions on.
Why do illusions matter?
-It matters because scientists believe the same basic processes underlie many of our more complicated perceptions and thoughts. Neuroscience, then, can help explain stubborn polarization in our culture and politics, and why we’re so prone to motivated reasoning.
-This is particularly true when ambiguity is at play i.e. when the information we are given is unclear (we see what we want to see).
