Senses and PerceptionChapter 4 Questions

Senses and Perception• All incoming sensation is interpreted by the brain• Without much conscious effort, we are constantly

taking in information about the world and sending it to our brains to make sense of it.

• Well our senses do provide us with reasonably reliable information, the representations they give us of the world are not as literally accurate a we tend to believe….

“Top” “Bottom” “Side”• We assign a top, bottom and side to most

objects we know—and keep them that way, regardless of their position.

-There is meaning given by the brain to a symbol-The object will remain the same in your mind

How many squares do you see?

• 16, 21, 30??• All of us see the same grid, but each of us

interprets it differently?-What does this tell us about how we perceive the world?

We all see it differently

The Big Five/ Senses

Each of our senses delivers a unique contribution in helping us understand our external world !

Vision • Most people would say they would rather lose

their hearing than sight. • From an evolutionary standpoint, vision has

been our most important sense.

Vision • Here is how it works (basic):To start with, photoreceptors in our eyes gather light, convert its physical energy into neural messages, and send it to the brain for decoding and analyzing. Transduction happens in the retina, which is composed of light sensitive layers of cells at the back of the eye called rods and cones.

Blind Spot • All of us have a blind spot, a small part of the retina that is not

coated with photoreceptors, which creates a small gap in our visual field.

• We are not aware of our blind spot because our eyes compensate for each other, and our brains “fill in” the spot with the information that matches the background.

Check out page 94 of your text!Figure 4.4

Hearing

• If a tree falls in the forest and no one is there…does it make a sound?

Hearing and Sound

• Sounds are created when actions, like banging, cause objects, like drums, to vibrate. These vibrating objects push air molecules back and forth, and as a result change the air pressure.

• Sound waves travel into the ear, transfer from tissues to bones, and are transformed into fluid waves in the inner ear.

• These vibrations stimulate tiny hair cells that generate nerve impulses to the brain

Smell• Smell is our most primitive sense• Our sense of smell, may also be our sense linked

most closely with memory• Odors are chemical molecules. When they hit the

tiny hairs in our nose, the receptors translate them into nerve impulses, which are then relayed to the brain.

Taste• A taste bud can tell whether foods are sweet, bitter, sour or

salty, and that is about it. (Food critics rely on their sense of smell to distinguish subtle food flavors, more than on their ability to taste them)

• Your taste receptors, located on the upper side of your tongue, transduce chemical molecules dissolved in saliva to the taste center of your brain.

• Your taste buds are replaced every few days.

Touch• Your skin contains nerve endings that, when

stimulated by physical contact with outside objects, produce sensations of pressure, warmth and cold.

• These sensations are the skin senses, and you could not survive without them.

• Your sensitivity to touch is where you need it most, on your face, tongue and hands.

Putting it Together• After your senses take all that stimulation, your brain

still has to figure it all out. • If you have never been proud of your organizational

skills, your self esteem is about to get a boost!-Your brain has an amazing ability to sort objects by size, distance, proportion, colour, and many other categories!

Sensation • At what point does physical reality become human

reality? -How bright does a light have to be before we see it glowing?-What is the softest sound we can still hear?

You and your friend are stargazing and you point out a faint star. Your friend says he cannot see it, despite you describing and detailing the exact location! He just cannot see it!? Why is this so?

Absolute Threshold It may be because your friend’s absolute threshold for light is lower than yours. • Absolute Threshold: The smallest, weakest amount of

stimulus a person can detect.

Definitions • Adaptation: the gradual loss of attention to

unwanted sensory information (Ex: You forget that the school change room smells after you have been in there for 15 minutes)

Consider this…- How is sensation and perception, biological and cognitive?

Perception

• Perception is always a matter of interpretation and expectation.

• Since the word is something we’ve seen before, our mind can easily recognize it without actually having to think about it.

Perception Constancies • Size• Colour• Brightness• Shape• Space

Perceptual Constancies

Size Constancy• The ability to retain the size

of an object regardless of where it is located

Colour Constancy • The ability to perceive an

object as the same colour regardless of the environment

Perceptual Constancies

Shape Constancy • The ability to perceive and

object as having the same shape, regardless of the angle at which it is seen

Space Constancy • The ability to keep objects

in the environment steady by perceiving either ourselves or outside objects as moving

Perceptual Constancies

Brightness Constancy • The ability to keep an

objects brightness constant as the object is moved to various environments.

• The word constancy means holding steady. And this is what we must do to the world in order to maintain order and control , to make sense out of our environment.

Depth Perception

• Depth Perception: The ability to see the relation of objects in space

• Retinal Disparity: The differences between the two images provided by you two eyes.

Just close one eye and switchback and forth to see the differencesin the images your eyes perceive.

Perceptual Organization • The human brain is quite efficient. It looks for

organizational strategies that require the least amount of effort.

• Your brain automatically assumes that objects having something in common go together.

• Therefore we interpret things the way we think they should be, not the way they actually are.

Gestalt • Common Region• Similarity • Proximity • Closure

Gestalt

• Gestalt: An organized whole, shape or form

Principle of Common Region • Objects that are within the same region are

perceptually grouped together. (The signs on the show how the message is perceived differently when the words are grouped in different regions)

Principle of Similarity

• Grouping like things together

Principle of Proximity

• Grouping things together that are near one another

Principle of Closure

• Filling in the missing details of what is viewed.

Illusions• Illusions: Inaccurate perceptions

Muller-Lyer Illusion

Muller-Lyer Illusion Illusions• Most people think that

illusions are “mistakes” that we make. That is not really the case.

• Instead over the years we learn to change what we perceive so that the world makes more sense.

• Some have thought that the illusion occurs because the arrows draw the eyes in… This is not the case

• We tend to mentally stretch the one line

• Reversible figures: Illusion in which the same object is seen as two alternating figures.

Which way is this person spinning?

http://well.blogs.nytimes.com/2008/04/28/the-truth-about-the-spinning-dancer/?_r=0

If the image is too slow go to:

• This is simply an optical illusion called a reversible, or ambiguous, image.

• The silhouette image of the spinning dancer doesn’t have any depth cues.

• As a result, your eyes will sometimes see the dancer standing on her left leg and spinning to the right. And sometimes they will perceive her as standing on her right leg and spinning to the left.

• Most people, if they stare at the image long enough, will eventually see her turn both ways.

END• Check Maplewood for missing assignments• Check msmadsensclass.weebly.com to access

missing assignments• Hand in Assignments…

Yes you do… You have had plenty of time

END

Constancies

• http://www.learner.org/series/discoveringpsychology/07/e07expand.html

• Start at 17min