How We Make Sense of What we See

Perception – processing and interpreting sensory input

Sensation and perception

• Sensation: gathering of data using the 5 senses– Vision– Taste– Smell– Touch– Hearing

• Perception – interpreting that data. Occurs in the BRAIN

Example

• The eyes gather LIGHT from the environment• The occipital lobe interprets that information

into vision

The human eye

The Retina• Surface is covered

in photoreceptors• Photoreceptors:

rods and cones• Rods – for

contrast (black and white and light and dark)

• Cones – for seeing color (respond to light wavelengths)

What color….?

• Volunteer – when can you report the color of the object held at side by teacher, with accuracy?

• Explain why.• Draw a picture of the back of an eye (inside

view). Label retina, rods, cones, optic nerve.• Why is it easier to see stars from the corner of

your eyes?

Is what we see reality?

• Or does our brain processing (perception) sometimes “trick” us?

• Complete vision tests 1 – 7 on the sheet provided. FOLLOW ALL INSTRUCTIONS for the tests to work. Read the sheet carefully.

Afterimages! (part 8 on sheet)

http://izismile.com/2011/11/11/mind_blowing_afterimages_optical_illusions_3_pics_11_gifs.html

Write and answer these questions

• What is the “blind spot”?• What are rods and cones, and where are they

located?• What stimulus do eyes respond to?• Where does visual perception occur?• Do we see reality the way it is, or do we

“create” a visual reality in our brain? Explain?

HomeworkLink is on sheet

Bring sheet to class (eye dissection instructions on it)

http://www.purposegames.com/game/898

Optical illusions

• Perception is not an accurate representation of reality

• Processing vision is subject to lots of misinterpretation and contextual processing of info

Bottom-up processing:Processing of incoming sensory input as it travels up from the sensory organs to the brain. No prior knowledge affects interpretation.

Top-Down processing:The brain’s use of knowledge, beliefs, and expectations to interpret the sensory information.

O `oe ka wahine a ke alohaI laila i ka uluwehiku`u pua hone i ka la`i Hone `ana i kehau o Makiki`O wau kou aloha i ka noe kuahiwi He u`i no `oe i ke kulaI wili `ia me ka `ie`ie o Leilono Ha`ina mai ana ka puanaKu`u pua hone i ka la`ihe nani maoli no

Pua Hone (Honey Flower) - by Dennis Kamakahi

O `oe ka wahine a ke alohaI laila i ka uluwehiku`u pua hone i ka la`i Hone `ana i kehau o Makiki`O wau kou aloha i ka noe kuahiwi He u`i no `oe i ke kulaI wili `ia me ka `ie`ie o Leilono Ha`ina mai ana ka puanaKu`u pua hone i ka la`ihe nani maoli no

You are the woman that I love. There in the lush verdure is my honey flower in the calm.Kissed by the dew of MakikiI am your love in the mountain mist.You are a beauty on the plains.Entwined with the sacred `ie`ie vine of Leilono.This ends my story.For my honey flower in the calm, a true beauty, indeed

What’s happening here?

Contextual set:The use of the present context of sensory information to determine its meaning.

What kind of animal is this? Pattern recognition.

v

v

vv

v

vv

v

Figure-and-ground principle:The brain organizes sensory info into a figure and the (back)ground

Closure:The brain closes incomplete figures to form meaningful objects.

How many circles do you see?How many squares?How many triangles?

Depth Perception:Our ability to perceive the distance of objects is instinctual.Evolved to help us move though space, avoid predators, hunt prey. As parallel lines recede away from us, they converge. Visual Cliff

Retinal Disparity:Binocular; states that as the disparity between two retinal images increases, the distance of the object from us decreases. Try it with your fingers!

Which table is longer?

Follow the movement of the rotating pink dots

Stare at the black ” +” in the center, the moving dots turns to green.

If you concentrate on the + in the center, what happens?

Visual compensation and afterimages.

What do you see first?

How many people? Count before and after they shift.

Right or Left Brained? Can you see a man’s face in 3 seconds or less?

3 – 4 is average, 6 - 7 is good, 13 – 14 is great!

Why is perception important in our every day lives?

• Architecture – manipulating perception of space• Advertizing – making things look bigger• Filling packages – making it seem like you’re getting

more for your money• Human manipulation and persuasion of all types• Use of color is key. Examples:– Some colors look “cleaner”. What color are personal

hygiene product packaging?– Some colors jump out among the competition – what

color are chip and candy packages?– What colors are used in “healthy” food packages?

Key Concepts

– Eye anatomy: cornea, lens, retina, optic nerve etc– What our eyes detect (sensation)…– …is not necessarily what we “see” (perception)

• Perception can be top down (prior knowledge, context) or bottom up (pure interpretation of sensory data)• Context, prior knowledge, expectation, emotion all

affect what we perceive

Would you be more willing to buy this if it cost…..

Or…..

Or how about…

HomeworkLink is on sheet

Bring sheet to class (eye dissection instructions on it)

http://www.purposegames.com/game/898

Pig Eye Dissection

• Clear your desks.• Follow lab instructions carefully.• Use pins as directed, colors specified on LEFT.• Dispose of gloves and specimen. Clean and

return dissection kit in condition you received it.