1. Chapter 6 Sensation and Perception

2. Sensation & Perception
How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we select, organize, and interpret our sensations, the process is called perception.
Preview Question 1: What are sensation and perception? What do we mean by bottom-up processing and top-down processing?

3. Sensing the World
Bottom-up processing- analysis that begins with sensory receptors and works up the brain’s integration of Information
Top-down processing-information processing guided by higher level mental processes, as when we construct perceptions drawing on our experiences and expectations

4. The Basic Process
Receptor Cell= specialized cell that responds to a particular type of energy
Different stimuli affect how many neurons fire, which neurons are activated or inhibited by a signal, and the rate at which they fire (Chapter 2).

5. Sensory Thresholds
Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
Our senses are remarkable low
Proportion of “Yes” Responses
Stimulus Intensity (lumens)
Preview Question 2: What is are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence?

6. Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Preview Question 3: What is the function of sensory adaptation?
Put a band aid on your arm and after awhile
you don’t sense it.

7. Thresholds (cont).
Difference Threshold= the SMALLEST change in stimulation that can be detected 50% of the time.
Adding a 1 pound weight to 10 pounds vs. 100 pounds

8. Subliminal Threshold (Perception)
Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness.
Kurt Scholz/ Superstock

9. Blindfold Activity

10. Vision
70% of our body’s sense receptors are located in the eyes.

11. The Eye
Preview Question 5: How does the eye transform light energy into neural messages?

12. Parts of the eye
Cornea: Transparent tissue where light enters the eye.
Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light.
Lens: Focuses the light rays on the retina.
Retina: Contains sensory receptors that process visual information and sends it to the brain.

13. The Lens
Lens: Transparent structure behind the pupil that changes shape to focus images on the retina.
Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

14. Retina
Retina: The light- sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information.
Rods: responsible for night vision; light & dark
Cones: responsible for color vision (less sensitive)

15. Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster.

16. Test your Blind Spot
Use your textbook. Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At some point the car on the right will disappear due to a blind spot.

17. Visual Adaptation
The sensitivity of rods and cones changes according to how much light is available.
Light and Dark adaptation
More auto accidents at night
Afterimage = sense experience that occurs after a visual stimulus has been removed

18. Stare at the dot for 30 seconds

20. Bipolar & Ganglion Cells
Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which converge to form the optic nerve.

21. Physical Characteristics of Light
Wavelength (hue/color)
Intensity (brightness)

22. Wavelength (Hue)
Hue (color) is the dimension of color determined by the wavelength of the light.
Wavelength is the distance from the peak of one wave to the peak of the next.

23. Wavelength (Hue) 150 distinct hues
Violet
Indigo
Blue
Green
Yellow
Orange
Red
400 nm
700 nm
Short wavelengths
Long wavelengths
Different wavelengths of light result
in different colors. Primarily (red, green blue)

24. Intensity (Brightness)
Intensity: Amount of energy in a wave determined by the amplitude. It is related to perceived brightness.

25. Intensity (Brightness)
Blue color with varying levels of intensity.
As intensity increases or decreases, blue color
looks more “washed out” or “darkened.”

26. Color Vision
Trichromatic theory: Young and von Helmholtz suggested that the eye must contain three receptors that are sensitive to red, blue and green colors.
Standard stimulus
Preview Question 7: What theories help us understand color vision?
Comparison stimulus
Max
Medium
Low
Blue
Green
Red

27. Color Blindness
Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory.
Ishihara Test

28. http://education-portal.com/academy/lesson/how- does-vision-work.html

29. Vision and Hearing These two senses dominate human consciousness.
Gather information about our environment

30. Hearing The Stimulus Input: Sound Waves
Sound waves are compressing and expanding air molecules.
Preview Question 8: What are the characteristics of air pressure waves that we hear as sound?

31. Sound Characteristics
Frequency (pitch) cycles per second
Intensity (loudness)

32. Intensity (Loudness)
Intensity (Loudness): Amount of energy in a wave, determined by the amplitude, relates to the perceived loudness.

33. Loudness of Sound
Richard Kaylin/ Stone/ Getty Images
120dB
70dB

34. Localization of Sounds
Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound.
Preview Question 11: How do we locate sounds?

35. Sound test
ringtones.com/

36. Frequency (Pitch)
Frequency (pitch): The dimension of frequency determined by the wavelength of sound.
Wavelength: The distance from the peak of one wave to the peak of the next.
Preview Question 10: What theories help us understand pitch perception?