1. Sensation and Perception
Tuesday, October 28
Sensation and Perception
Sensation: your window to the world
Perception: interpreting what comes in the window.

2. Sensation vs. Perception
“The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.”
“The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.”
The brain receives input from the sensory organs.
The brain makes sense out of the input from sensory organs.
Sense:
especially vision and hearing
smell, taste, touch, pain, and awareness of body position
How do the sense organs and nervous system handle incoming sensory information?
How does the brain turn sensory information into perceptions?
Why is our style of creating perceptions better at perceiving the real world than at decoding tricky optical illusions?

3. Making sense of the world
Top-down processing:
using models, ideas, and expectations to interpret sensory information
What am I seeing?
Bottom-up processing:
taking sensory information and then assembling and integrating it
Click to reveal definitions for bottom-up and top-down processing.
Is that something I’ve seen before?

4. Top-down Processing
You may start to see something in this picture if we give your brain some concepts to apply:
“tree”
“sidewalk”
“dog”
“Dalmatian”
Click to reveal sidebar and hints one by one.

5. Anything below this threshold is considered “subliminal.”
Thresholds
The absolute threshold refers to the weakest mount of a stimulus that can be sensed.
Anything below this threshold is considered “subliminal.”
No animation.
Instructor: You could first present this question using a specific sense, such as “How loud does a sound have to be before you can detect it?”
A.T. has been determined for all senses, but remember! They differ from human to human.

6. When Absolute Thresholds are not Absolute
Signal detection theory refers to whether or not we detect a stimulus, especially amidst background noise.
This depends not just on intensity of the stimulus but on psychological factors such as the person’s experience, expectations, motivations, and alertness.
No animation.
For example, parents of newborns can detect a faint baby’s cry that for others would not stand out from background noise.

7. Just Noticeable Difference
The minimal amount of difference that can be detected between two stimuli
Volume on a TV
Weight of two books
Paint chip colors

8. Sensory Adaptation
To detect novelty in our surroundings, our senses tune out a constant stimulus.
The rock in your shoe or the ticking of a clock are more difficult to sense after a while.
We don’t notice this visually because normally our eyes are constantly moving.
However, if you concentrate on keeping your eyes in one spot, you’ll see the effects, as your eyes adjust to stimuli in the following slides.
Click to reveal bullets.
To prepare for this slide, at the beginning of class you could ask students to tuck a pen behind one ear, and by the time they get to this slide, ask if they feel it.
Or ask whether they feel the cell phone in their pockets, and then ask them to switch to the opposite pocket and see if they notice it more.

9. Vision

10. The Eye
Light from the candle passes through the cornea and the pupil, and gets focused and inverted by the lens. The light then lands on the retina, where it begins the process of transduction into neural impulses to be sent out through the optic nerve.
The lens is not rigid; it can perform accommodation by changing shape to focus on near or far objects.
Click to reveal bullets.

11. Pupil: opening in the colored part of the eye, determines amount of light that enters
Lens: adjusts to the distance of objects by changing thickness, behind the pupil helps focus images on the retina
Retina: light sensitive inner surface, containing rods, cones and neurons

12. More Eye Stuff
Blind Spot: point at which optic nerve leaves the eye, eye registers nothing because area lacks photoreceptors
Optic Nerve: never that carries neural impulses from the eye to the brain
Fovea: central focal point in the retina

13. Photoreceptors Neurons that are sensitive to light
Rods: sensitive to brightness of light, “black and white”
Cones: provide color vision

14. Color Blindness
People missing red cones or green cones have trouble differentiating red from green, and thus have trouble reading the numbers to the right.
Opponent-process theory refers to the neural process of perceiving white as the opposite of perceiving black; similarly, yellow vs. blue, and red vs. green are opponent processes.
Click to reveal text boxes.
Instructor: you could add, “Some people say that dogs have “black and white” vision. In fact, they are lacking red receptors, so their vision has simpler color perception, dichromatic, not monochromatic.”
Feeling superior to animals? Note that many birds and insects can sense ultraviolet and infrared that you can’t see.

15. Color Vision
Young-Helmholtz Trichromatic (Three-Color) Theory According to this theory, there are three types of color receptor cones--red, green, and blue. All the colors we perceive are created by light waves stimulating combinations of these cones.
No animation.
Instructor: you could start by saying that we see the color of an orange because it absorbs all light except the wavelengths that our brain interprets as orange.
You could note that the red, green and blue don’t actually refer to the appearance of the cones; they are the colors to which these three cones react.

16. Opponent -Process Theory
Red- Green, Yellow-Blue, Black- White
Staring at one color for a long time causes the cone to become fatigued. So when color is removed, the complementary color is what is seen.
Causing Afterimages: visual impression that remains after the original images are removed.

17. Opponent-Process Theory Test
Instructor: Tell the students: “Stare at the center dot for 30 seconds; if you’re doing it well, the flag will start to disappear. If it does, keep staring at the dot.”
Further narration as they stare at the dot: “If opponent-process theory is correct, then fatiguing our perception of one will make a blank slide look like the opposite color… and the opponent processes are white vs. black, red vs. green, and yellow vs. blue.”
Click to make flag disappear.
What do you see?
Question for students: “Besides opponent-process theory, what else are we demonstrating here?”...(sensory adaptation).
After our color receptors for green become fatigued, an empty white background will briefly seem red, just as plain water might taste salty or strange after eating a lot of intensely sweet candy to the point of fatiguing our tongue.
There have been versions of this circulating online in which our receptors get fatigued just by some dots near the center dot, and a B&W picture turns to full color when we look at a blank space.
The dot, the dot, keep staring at the dot in the center…

19. Hearing

20. Synethesia

21. Mixing the different senses together
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Sensory interaction occurs when different senses influence each other.
For example:
a burst of sound makes a dim light source more visible.
flavor is an experience not only of taste, but also of smell and texture.
seeing text or lip movement, or even feeling the puff of air from consonants, affects what words we hear.
Synaesthesia is a condition when perception in one sense is triggered by a sensation in a DIFFERENT sense.
Some people experience synaesthesia all the time, reporting that, “the number 7 gives me a salty taste” or “rock music seems purple.”
Click to reveal bullets.

22. Sound Perception: Loudness
Loudness refers to more intense sound vibrations. This causes a greater number of hair cells to send signals to the brain.
Soft sounds only activate certain hair cells; louder sounds move those hair cells AND their neighbors.
Click to reveal bullets.

23. Sound Perception: Pitch
-Pitch: tone’s experienced highness or lowness, depends on frequency
-Frequency: number of complete wavelengths that pass a
point in a given time
Click to reveal three text boxes.

24. Percieving Sound
Place theory
At high sound frequencies, signals are generated at different locations in the cochlea, depending on pitch. The brain reads pitch by reading the location where the signals are coming from.
Frequency theory
At low sound frequencies, hair cells send signals at whatever rate the sound is received.

25. Sound Waves Reach The Ear
The outer ear collects sound and funnels it to the eardrum.
In the middle ear, the sound waves hit the eardrum and move the hammer, anvil, and stirrup in ways that amplify the vibrations. The stirrup then sends these vibrations to the oval window of the cochlea.
In the inner ear, waves of fluid move from the oval window over the cochlea’s “hair” receptor cells. These cells send signals through the auditory nerves to the temporal lobe of the brain.
Click to show details about outer, middle, and inner ear.

26. Preventing Hearing Loss
Exposure to sounds that are too loud to talk over can cause damage to the inner ear, especially the hair cells.
Structures of the middle and inner ear can also be damaged by disease.
Prevention methods include limiting exposure to noises over 85 decibels and treating ear infections.
People with conduction hearing loss may be helped by hearing aids. These aids amplify sounds striking the eardrum, ideally amplifying only softer sounds or higher frequencies.
People with sensorineural hearing loss can benefit from a cochlear implant. The implant does the work of the hair cells in translating sound waves into electrical signals to be sent to the brain.

27. Hearing Loss
Conductive hearing loss: damage to the middle ear, this is damage to the mechanical system that conducts sound waves to cochlea
Sensorineural hearing loss: damage to the inner ear, damage to cochlea’s receptor cells (auditory nerves)

28. Cochlear implants “artificial ears” “bionic ear”
Wired into cochlea’s nerves, transmits sounds into electrical signals that convey information about sound to the brain

30. Touch
Combination of pressure, temperature and pain

31. 1. Pressure
Sensory receptors around the roots of hair cells fires when area of skin is touched. -more sensitive areas are lips, nose, fingertips, and cheeks Pressure undergoes adaptations: EX: Hand holding

32. 2. Temperature Neurons just beneath the skin
Warmth: touch a stove, receptors are firing warmth
Cold: cool towel on forehead, recepetors are firing cool

33. 3. Pain “Girl Who Can’t Feel Pain”
Gate Theory: Only a certain amount of information can be processed by the nervous system at a time. Spinal cord has a “gate” that allows or blocks pain signals to the brain.

34. Sensing Body Position and Movement
Kinesthesis (“movement feeling”) refers to sensing the movement and position of individual body parts relative to each other.
How it works: sensors in the joints and muscles send signals that coordinate with signals from the skin, eyes, and ears
Without kinesthesis, we would need to watch our limbs constantly to coordinate movement.
Click to reveal bullets.

35. Sensing Body Position and Movement
Vestibular sense refers to the ability to sense the position of the head and body relative to gravity, including the sense of balance.
How it works: fluid-filled chambers in the inner ear (vestibular sacs and semicircular canals) have hairlike receptors that send messages about the head’s position to the cerebellum
Vestibular sense serves as the human gyroscope, helping us to balance and stay upright.
Click to reveal bullets.

36. Smell and Taste

37. Neurochemistry of Taste
Sweet, Sour, Salty, Bitter, and Umami (savory/ meaty)
There are no regions of the tongue, just different types of taste receptor cells projecting hairs into each taste bud’s pore.
These cells are easily triggered to send messages to the temporal lobe of the brain.
Burn your tongue? Receptors reproduce every week or two. But with age, taste buds become less numerous and less sensitive.
Flavor depends on odor, texture, and temperature and taste.
Click to reveal bullets.

38. Smell
Chemical sense that helps you recall the most memories as well as helps with taste
Odors are detected by receptor neurons high in the nostrils. These receptors send information about the odors to the brain via the olfactory nerve.