We will cover the basic human senses, and describe the basic neuroanatomy of how we process distinct signals in each modality. We also discuss vision and perception in depth. We look at many illusions!! Make sure to view the slides and see if these illusions are able to trick your mind :O. Your brain may end up playing tricks on itself by the end of the hour!

1. Lies Our Brains Tell
Us!!

3. Your brain is lying to you...

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VISION
● Involves 30% of human cerebral cortex
● Light passes through cornea (initial
focusing) → enters eye (pupil)
● Iris regulates amount of light entering
(changes pupil size)
● Lens bends light to focus on inner eyeball
surface (retina)
● Signals get processed by retina’s
specialized cells and then travel to other
parts of brain for further integration &
interpretation (via optic nerves)

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7. Eye Anatomy
ORDER OF STRUCTURES THAT
LIGHT GOES THROUGH:
(1) Cornea → (2) Pupil → (3) Lens →
(4) Retina → (5) Optic Nerves

8. Visual perception is the ability to interpret the surrounding environment using light in the
visible spectrum reflected by the objects in the environment.
This is different from visual acuity, which refers to how clearly a person sees (for
example "20/20 vision").
A person can have problems with visual perceptual processing even if they have 20/20
vision.
Visual perception is considered a dynamic process that goes far beyond simply
replicating the visual information provided by the retina. 8
VISUAL PERCEPTION

10. “It’s really important to understand we’re not seeing reality,” says
neuroscientist Patrick Cavanagh. “We’re seeing a story that’s being created
for us.”
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Optical Illusions: When Your Brain Can't Believe
Your Eyes
Look at an optical illusion and you may think you're seeing things -- such as a curved
line that's actually straight, or a moving object that's standing still. You wonder if
your eyes are playing tricks on you.
It's not your eyes. An illusion is proof that you don't always see what you think you
do -- because of the way your brain and your entire visual system perceive and
interpret an image.

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13. MUFFIN PAN ILLUSION
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17. Lateral Retinal Inhibition
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Hermann grid → gray spots appear at
the intersections of the rows and
columns created by the squares,
because of a phenomenon called
lateral retinal inhibition.
If you stare directly at one of these
intersections, however, the gray spot
disappears, and it looks white,
because then you are using the cells of
the fovea, which do much less
correction for an area's surroundings.

18. Lateral Retinal Inhibition
Lateral inhibition occurs when the activity of one cell suppresses the activity of a
nearby cell. ... For example, without lateral inhibition, the border between a black
tile and a while tile would appear less obvious.
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19. MUFFIN PAN ILLUSION
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What happens in illusions
● Illusions occur due to an imbalance in brain perception
and vision
● when the brain attempts to generate a perception, it
basically is taking a guess at the near future by trying to
fast-forward a tenth of a second.
● "Illusions occur when the brain attempts to perceive the
future, and those perceptions don't match reality,"

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23. Moving patterns illusion explained
- Illusory motion
- Only movement comes from your
eyes
- Illusory motion activated areas of
the brain that are responsible for
real movement
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27. Gray shapes illusion explained
- Brightness illusion
- Our brain doesn’t perceive
true colors of brightness
- It uses surrounding colors to
compare brightness
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30. Two perceptions illusion explained
- Ambiguous figures illusion
- Two perceptions are
mutually exclusive
- See one or the other but not
both
- Object never changes, but
our view of it does
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31. Why do we see them?
- The neural machinery that interprets visual,
auditory, and other sensory inputs also interprets
dreams and delusions
- Brain makes inferences based on visuals
- Neuronal feedback could be what makes us see
these illusions
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“The Dress”
White & Gold or
Blue & Black?

33. “The Dress” explained
- Pascal Wallisch: neuroscientist at NYU
- The type of light we assume is being
cast on the dress alters our views
- Brain unconsciously filters light; leads
to color judgment
- Different people use different filter
schemes
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34. Pascal Wallish’s discovery
- Conducted a study on 13,000 people
- Found a correlation between dress perception and
the time you (naturally) go to bed and wake up
(chronotype)
- Night owls: black & blue
- Early birds/larks: white & gold
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35. Wallisch’s Hypothesis
- People who wake up early tend to
spend more time in daylight
- They assume the dress is
illuminated by daylight
- Bright sun has a lot of blue in it, so
their brain filters it out; white &
gold
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- Night Owls spend less
time in daylight
- They assume the dress is
illuminated by artificial
light
- They filter the dress to
appear black & blue
*Rather than chronotype, we should measure daylight
exposure

36. Do you think Wallisch has solved the
mystery of the dress? Why or why not?
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37. Is his theory true?
Yes!
- Explains a large part of individual
differences
- But there's more factors….
- Prior experience
- Personality
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38. What do we learn from this?
- When faced with the unknown, the brain leans on
familiarity
- “People assume what they see more of”
- Brain subconsciously makes inferences all the time
- Don’t always know if your brain is making inferences or
not
Our life history alters the way our brain perceives
things!
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40. Gazing illusion explained
- That alternating black-white patch
inside the object suggests diagonal
motion and confuses our senses.
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43. Flash-Lag Illusion explained
- 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.
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47. “It’s really important to understand we’re not seeing reality,” says neuroscientist Patrick
Cavanagh. “We’re seeing a story that’s being created for us.”
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48. Auditory Illusions
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49. HEARING
● Auditory system
● Picks up various qualities
of detectable signals of
sound: pitch, loudness,
duration, location
● Analyzes complex sounds,
breaks them into separate
components or frequencies

50. Can You Hear Me Now?
1. Sound reaches pinnae of ears, funneled to ear canals to
reach eardrum (tympanic membrane)
2. Eardrum vibrates in response
3. Vibrations sent to 3 bones - hammer, anvil, stirrup
4. Stirrup acts as piston, pushes on oval window (separates
air-filled middle ear from fluid-filled snail-like cochlea)
5. Oval window converts mechanical vibrations into pressure
waves in cochlea
6. Waves transduced into electrical signals by hair cells
(specialized receptor cells)

51. McGurk Effect
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https://www.youtube.com/watch?v=2k8fHR9jKVM

52. Cognitive Bias
Bias
Thinking &
Decision
Making
No one is
immune to
bias
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53. Blind Spot Bias : Easier to spot in
everyone else.
Only paying attention
to news stories that
confirm our opinions
Attributing success of
other people as luck
but taking credit for
our own
accomplishments
WE ARE ALL GUILTY
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Mental shortcuts - heuristics
For example, when trying to decide if you should drive
or ride the bus to work, you might suddenly remember
that there is road construction along the bus route. You
realize that this might slow the bus and cause you to be
late for work. So you leave earlier and drive to work on
an alternate route. Heuristics allow you to think through
the possible outcomes quickly and arrive at a solution.

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For example, if you are thinking of flying and suddenly
think of a number of recent airline accidents, you might
feel like air travel is too dangerous and decide to travel
by car instead. Because those examples of air disasters
came to mind so easily, the availability heuristic leads
you to think that plane crashes are more common than
they really are.

60. Thank You!