Unit 4: Sensation and Perception Energy Senses, Chemical Senses, Body Position Senses, Perception, Thresholds, Perceptual Theories, Principles of Visual

Unit 4: Sensation and PerceptionEnergy Senses, Chemical Senses, Body Position Senses, Perception, Thresholds, Perceptual Theories, Principles of Visual Perception, Effects of Culture on Perception

Presentation #2

How is temperature sensed in the skin through thermoreceptors?

Thermoreceptors are responsible for the sensation of non-painful warmth or cold sensations.

They have ion channels that change voltage across the nerves in relation to temperature.

Have you ever turned the water on really hot and it felt cold?

How does our brain process sensory information?

How does thermosensation keep us alive?

The main function of thermosensation is to maintain homeostasis.

One of the most important examples of homeostasis is the regulation of body temperature which is controlled by the specific areas in the hypothalamus that receive information form thermoreceptors in the skins and in some of the major blood vessels..


Energy Senses

Vision

Hearing

Touch


How do our eyes collect information from the outside world?

Do Now: Do you think the color “green” is the same for you as it is for me? Explain your answer.

Homework: bring in a plastic top of a container (example: the top of a coffee can)

The Eye



What is Vision?

Vision is our dominant sense in human beings.

There are many steps in gathering visual information.


Step One

Light is reflected off objects and are gathered by the eye.

The color we perceive depends on several factors: Light intensity (energy) Light wavelength (determines hue)


The Light Spectrum

ROY G. BIV


Step Two The reflected light first enters the eye through the

cornea

The light then goes through the pupil

The pupil is like the shutter of a camera

The muscles that control the pupil (the iris) open it to let more light in, or make is smaller to let less light in.


Step Two continued

Through a process called accommodation, the light is then focused by the lens.

Try This: Hold up one finger and focus on it for a few seconds. Now focus on the wall behind your finger. Now refocus on your finger. Do you see the change? This is your lens working!


Step Three: Transduction

Transduction: the translation of incoming stimuli into neural signals.

This is done in the cells called cones and rods.

Cones are activated by color

Rods are activated by black and white.


Where will these messages be sent in the brain?

Activity

Benham’s Disks

Remember: the reason behind this illusion remains unresolved!


Our Blind Spot What is a “blind spot”?

Humans have blind spots.

Our blind spot is the area on the retina that does not have receptors that respond to light.


Activity

Let’s find out blind spot!

Close your right eye.

Hold your blind spot tester strip about 20 inches from your face.

With your left eye, look at the smiley face and slowly pull the tester towards your face.

Did you see the sad face disappear?


Step Four: In the Brain

The information collected by our eye is sent to the occipital lobes of our brain.

This is where some researchers say sensation ends and perception begins.



Hubel and Weisel

Perception researchers.

They discovered that groups of neurons in the visual cortex respond to different types of visual images.

The visual cortex has feature detectors for vertical lines, curves, and motion.


What two theories are used to explain Color Vision?

Do Now: have you ever stared at an image and then closed your eyes and you see a different color?

Trichromatic Theory

Trichromatic Theory was created by Thomas Young and Hermann von Helmholtz.

They hypothesized that we have three types of cones I the retina.

These cones detect the different colors blue, red and green.


Trichromatic Theory: the experiment

Helmholtz used color-matching experiments where participants would alter the amounts of three different wavelengths of light to match a test color.

Participants could not match the colors if they used only two wavelengths, but could match any color in the spectrum if they used three.


Trichromatic Theory

This theory fails to explain visual phenomena such as afterimages and color blindness.


Afterimages Test


Stare at the green box on the next slide.Close your eyes.

What color do you see?

Afterimages Test


Stare at the yellow box on the next slide.Close your eyes.What color do you see?

What happened???

Why do you think you saw a different color when you closed your eyes?


Dichromatic Color Blindness

Someone with Dichromatic Color Blindness cannot see either red/green shades or blue/yellow shades.

Color Blindness Test #1

Color Blindness Test #2


http://www.toledo-bend.com/colorblind/Ishihara.asp

http://colorvisiontesting.com/online%20test.htm

Monochromatic Color Blindness

Someone with Monochromatic Color Blindness only sees shades of grey.


Opponent-Process Theory

This theory states that the sensory receptors arranged in the retina come in pairs:

Yellow/blue

Red/green

Black/white

If one sensor is stimulated, its pair is inhibited from firing.


Critical Thinking

How does Opponent-Process Theory of Color Vision explain the visual phenomena of afterimages and colorblindness?


Summary

A combination of both the Trichromatic Theory and the Opponent-Process Theory are necessary to fully explain color vision.

WHY???


How does our sense of hearing work?

Do Now: how come dogs can hear some things we can not?

Auditory Sense

Our auditory sense used energy in the form of waves.

This is just like what other sense?

Sound waves are created by vibrations, which travel through the ear, and are collected by our ears.


Try This!

Be as quiet as humanly possible.

Write down every noise that you hear.


Our ears collect waves

Sound waves are collected in our outer ear, or pinna.

The waves travel down the ear canal.

The waves reach the eardrum or typanic membrane.


In the Middle Ear The ear drum connects with the hammer

The hammer is connected to the anvil

The anvil is connected to the stirrup


In the Inner Ear The vibration of the ear drum is

transmitted by the middle ears to the oval window.

The oval window is attached to the cochlea.

The cochlea is filled with fluid and lined with hair cells which connect to neurons

The fluid in the cochlea moves when the oval window is stimulated by the middle ear. This causes the hair to move which then activates the neurons.


Cochlear Implants


Cochlear Implants


Pitch Theories

How do we hear different pitches or tones?

Place Theory

According to Place Theory, the hair cells in our cochlea respond to different frequencies of sound based on where they are located in the cochlea.

Some of these hairs bend in response to high pitches, some to low.

Frequency Theory

Research demonstrates that place theory explains how hair cells sense high tones, but not low tones.

Lower tones are sensed by the rate at which the cells fire.

This theory states that we sense pitch because the hair cells fire at different rates or frequencies

How does our understanding of how hearing works help us to understand

deafness?

Deafness occurs when something goes wrong with the system of conducting the sound to the cochlea.

Our Sense of Touch

Do Now: why is our sense of touch considered an energy sense?

Touch: the last energy sense When our skin is indented, pierced or

experiences a change in temperature, our sense of touch is activated by this energy.

Some nerves respond to temperature, while others respond to pressure.

If our temperature receptors are stimulated sharply, pain receptors will fire. This is to warn us of potential dangers.

why is our sense of touch considered an energy sense?

Gate-Control Theory

Gate-Control Theory explains that some pain messages have a higher priority than others.

When a “high priority” pain messages is sent, the “gate” is opened for that sensation and closed for all others.

How does this explain the sensation of having an itch and then scratching it?

why is our sense of touch considered an energy sense?

Summary

Explain touch through concepts you have learned in our unit on neuroanatamy.

What role do thermoreceptors play in our sense of touch?

How do our Chemical Senses work?

Do Now: which of our 5 senses are chemical senses?

Our Sense of Taste

http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP14104

Our Sense of Taste (Gustation)

Our taste buds are located on papillae which are the bumps on our tongue.

We sense four types of tastes:

Sweet

Salty

Sour

Bitter


Sense of Taste continued…

The more densely packed our taste buds, the more chemicals we absorb.

The more chemicals absorbed, the more intense the food tastes.

The flavor of food is actually a combination of taste and smell.


Our Sense of Smell (Olfaction)

Our sense of smell depends on chemicals.

Molecules of substances rise in the air and are drawn into our nose.


Our Sense of Smell continued…

Molecules enter the nose and settle in a mucous membrane at the top of each nostril and are then absorbed by receptor cells.

Researchers estimate that there are over 100 different types of receptor cells.

These cells are attached to the olfactory bulb which sends the information to the brain.

Information is sent to the amygdala and then the hippocampus.

The hippocampus is part of the limbic system which is responsible for emotional impulses and memories.


Aim: What are our body position senses?

Do Now: how is body position a sense?

Vestibular Sense Our vestibular sense tells us about how

our body is oriented in space.

The inner ear is crucial in this process.

Think about riding a roller coaster…sometimes you get nauseous and/or dizzy.



Kinesthetic Sense

Our kinesthetic sense gives us feedback about the position and orientation of specific body parts.

Because of this sense, you can touch your knee with no difficulty because your kinesthetic sense detects where your knee is in relation to your hand.


Summary

How do our body position senses use our chemical and energy senses to function properly?

What are the principles of Visual Perception?

Do Now: how does an optical illusion work?

Figure-Ground Relationship

When we look at an image, part of our perception of that image is the figure-ground relationship.

This is when our brain determines which part of the image is the figure, and which is the background.


Optical Illusions

Let’s examine the following optical illusions together!


What do you see?


What do you see?


What do you see?


What do you see?


What are the principles of Gestalt Psychology in relation to visual

perception? What is Gestalt Psychology?

Gestalt Psychologists observe people in the “real world” and focus on the whole, not the parts.

Gestalt Rules

Gestalt Psychologists say that we perceive images a part of a group, not isolated elements.

Gestalt Psychologists thought this process was innate and inevitable (meaning its nature)


Gestalt Rules

Proximity: objects that are close together are more likely to be perceived as belonging to the same group.


Gestalt Rules

Similarity: Objects that are similar in appearance are more likely to be perceived as belonging in the same group.


Gestalt Rules

Continuity: Objects that form a continuous form are more likely to be perceived as belonging to the same group.


* * * * * * * * * *

Gestalt Rules

Closure: Similar to top-down processing. Objects that make up a recognizable image are more likely to be perceived as belonging in the same group even if the image contains gaps that the mind needs to fill in.


Summary

How do the Gestalt Rules of visual perception apply to people? Give specific examples.

Complete the worksheet INDIVIDUALLY!!!


What is Constancy?

Do Now: what does it mean to be constant?


Constancy

Every object we look at changes slightly due to a variety of reasons. Our angle of vision Variations in light


Constancy

Our ability to maintain constant perception of an object despite these changes is called constancy.


Types of Constancy

Size Constancy: we keep a constant size in mind for an object.

Because of this, it does not matter if we are far away or close up to the object.


Types of Constancy

Shape Constancy: we keep a constant shape in our mind for each object.

no matter what angle we look at the object, we know what shape the object is supposed to be.


Types of Constancy

Brightness Constancy: we perceive objects as being a constant color even as the light reflecting off of the object changes.


Summary

Give one example of how we use constancy everyday.


What is Perceived Motion?

Do Now: have you ever seen a flip book? How do they work?


Perceived Motion

Our brains are able to detect how fast images move across our retinas and take into account our own movement.

Sometimes, our brain perceives objects to be moving when they are not.

The stroboscopic effect is an example of this and is used in flip books.


Cooperative Learning Activity

You will create a flip book with a partner!

You will only have the rest of the period to complete it!

Use stick figures to save time (keep it simple!)


How do Flip Books demonstrate Perceived Motion?

Perceived Motion continued…

Phi Phenomenon: when a series of light bulbs are turned on and off at a particular rate will appear to be one moving light. Example: movie marquees and holiday lights

Autokinetic Effect: if a spot of light is projected steadily on the same place on a wall of a dark room, it will appear to move if you stare at it.


Summary

Give an example for each of the following phenomenon: Stroboscopic effect Phi phenomenon Autokinetic effect


How did Eleanor Gibson use the Visual Cliff Experiment to explain depth cues?

Do Now: have you ever jumped into a pool? How did you know how far away the water was?


Visual Cliff Experiment

Eleanor Gibson designed the Visual Cliff Experiment to see if infants had developed depth perception.

What is depth perception?

Depth perception allows us to view the world as 3 dimensional, not 2 dimensional.


What is the Visual Cliff Experiment?

A visual cliff involves an apparent, but not actual drop from one surface to another.

A visual cliff is created by connecting a transparent (see through) glass surface to an opaque patterned surface.

The floor below has the same pattern as the opaque (can’t see through it) surface.

This apparatus creates the visual illusion of a cliff, while protecting the subject from injury


What is the Visual Cliff Experiment?


Psychologists have determined that depth perception develops when we are about 7 month old.

What cues do we use to determine depth?

Monocular Cues: artists use these cues are used to imply (suggest) depth in their drawings.

Linear Perspective

Relative Size Cue

Interposition Cue

Texture Gradient

Shadowing


Linear Perspective


Relative Size Cue


Interposition Cue


Texture Gradient


Shadowing


What cues do we use to determine depth?

Binocular Cues: binocular cues result from our anatomy (nature).

Binocular disparity: We see the world through two eyes are a certain distance apart, and this feature gives us the ability to perceive depth.

Convergence: as an object moves closer to our face, we cross our eyes to maintain focus.


Does culture effect our perception?

Research indicates that some of perceptual rules are learned (nurture).

Examples: linear perspective in art and optical illusions.


Muller-Lyer Illusion


Unit Exam!

You will have an exam on the following:

Energy senses: sight, hearing and touch

Chemical senses: taste and smell

Body position senses: vestibular and kinesthetic sense

Perception: thresholds

Perceptual theories: signal detection theory, top-down and bottom-up processing

Principles of visual perception: figure-ground, gestalt rules, constancy, perceived motion and depth cues

Documents

Unit 4: Sensation and Perception Energy Senses, Chemical Senses, Body Position Senses, Perception, Thresholds, Perceptual Theories, Principles of Visual