1. Sensation and Perception
Chapter 3

2. LO 3.1 Sensation and the central nervous system
Sensation - the activation of receptors in the various sense organs.
Sensory receptors - specialized forms of neurons.
Sense organs:
eyes
ears
nose
skin
taste buds
Sensation occurs when special receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain.
Instead of receiving neurotransmitters from other cells, these receptor cells are stimulated by different kinds of energy.
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3. Eye Sensory Receptors
Sensory receptor

4. Ear Sensory Receptors
Sensory
receptors

5. Nose Sensory Receptors

6. Skin Sensory Receptors
Pain
Light touch
Cold
Heat
Hair movement
Strong pressure

7. Sensation and Perception
Stimulus energy
Heat
Light
Sensory receptor
Eyes
Nose
Skin
Neural
impulse
Brain
Visual
Olfactory
Sensation
Perception

8. LO 3.1 Sensation and the central nervous system
Sensory Thresholds
Absolute threshold - smallest amount of energy needed for a person to consciously detect a stimulus (50% of time)
Just noticeable difference smallest difference between two stimuli that is detectable (50% of time)
When are sensations perceived
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9. Habituation and Sensory Adaptation
LO 3.1 Sensation and the central nervous system
Habituation and Sensory Adaptation
Habituation - tendency of the brain to stop attending to constant, unchanging information.
Sensory adaptation - tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging.
Turn off song
Sensory receptor cells for hearing are still responding to to the sounds, but the lower centers of the brain are not sending the signals from those receptors to the cortex.
Sensory receptor cells (taste, touch, smell, vision) become less responsive to a stimulus that is unchanging.
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10. Light
Amplitude
Wavelength

11. Psychological Aspects to Light
LO What is light
Psychological Aspects to Light
Brightness - amplitude of the wave; higher waves brighter; lower waves dimmer.
Color - length of the wave; long wavelengths red; short waves blue
Saturation - purity of the color people see
Saturation
Color
Brightness
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12. LO 3.3 How eyes see and see color
Structure of the Eye
Cornea – clear membrane that covers surface of eye; protects eye and focuses most of light coming into eye.
Pupil – hole through which light from the visual image enters eye.
Cornea
Pupil
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13. LO 3.3 How eyes see and see color
Structure of the Eye
Iris - round muscle; can change the size of the pupil, letting more or less light into the eye; helps focus the image.
Lens – suspended by muscles; finishes the focusing process begun by the cornea.
Lens
Iris
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14. LO 3.3 How eyes see and see color
Retina, Rods, and Cones
Photoreceptors that respond to various light waves
Rods – receptors responsible for non-color vision and sensitivity to dim light.
Cones – receptors responsible for color vision and sharpness of vision.
Retina
Cone
Optic nerve
Rod
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16. Visual Field of left eye
Visual field of right eye
Optic nerve
Optic chasm
Primary visual area

17. LO 3.3 How eyes see and see color
Color Vision
Trichromatic theory - theory of color vision that proposes three types of cones: red, blue, and green.
Opponent-process theory - theory of color vision that proposes four primary colors with cones arranged in pairs: red and green, blue and yellow
Three primary colors. Shades of color correspond to different amounts of light received by each of the three types of cones
Four primary colors. The cones are arranged in pairs Red with green and blue with yellow. Or Or
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18. If a person tires out one of the members of the pairs it weakens that members ability to inhibit the other cell. If person looks away from a red image there will be green after image as the other member of the pair fires away.

19. LO 3.3 How eyes see and see color
Color Blindness
Monochrome colorblindess - either have no cones or have cones that are not working at all.
Red-green colorblindess - either the red or the green cones are not working.
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20. Sound Amplitude Amplitude –volume (how soft or loud a sound is).
LO What is sound
Sound
Amplitude
Amplitude –volume (how soft or loud a sound is).
Wavelength –frequency or pitch
Purity –timbre (a richness in the tone of the sound).
Wavelength
Quieter
Louder
Sound waves= vibrations of the molecules of air.
Frequencies= herts ,000- humans; 50-60,000- dogs; Dolphins 200,000
Deeper pitch
Higher pitch
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21. LO 3.4 What is sound
Structure of the Ear
Auditory canal - short tunnel that runs from the pinna to the eardrum
Eardrum - thin section of skin that tightly covers the opening into the middle part of the ear
Eardrum
Auditory canal
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22. Structure of the Ear
When sound waves hit the eardrum, it vibrates and causes three tiny bones in the middle ear to vibrate.
Hammer
Anvil
Stirrup
Hammer
Hammer
Bones amplifies the vibrations from the ear drums
Stirrup, the last of these bones causes a membrane (oval window) covering the opening of the inner ear to vibrate.
Stirrup
Anvil

23. LO 3.4 What is sound
Structure of the Ear
Cochlea - snail-shaped structure of the inner ear that is filled with fluid.
Organ of Corti – rests in the basilar membrane; contains receptor cells for sense of hearing.
Organ of Corti
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24. Structure of the Ear Auditory nerve
Auditory nerve - bundle of axons from the hair cells in the inner ear; receives neural message from the organ of Corti.
Auditory
nerve

25. LO 3.4 What is sound
Theories of Pitch
Pitch - frequency of the sound waves; higher frequencies are perceived as higher pitches.
Place theory - states that different pitches are experienced by the stimulation of hair cells in different locations on the organ of Corti.
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26. LO 3.4 What is sound
Theories of Pitch
Frequency theory - states that pitch is related to the speed of vibrations in the basilar membrane.
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27. LO 3.6 Senses of taste and smell
Taste buds – taste receptor cells in mouth; responsible for sense of taste
Gustation - the sensation of a taste.
Five Basic Tastes:
Sweet
Sour
Salty
Bitter
“Brothy”
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28. Taste Bitter Taste pore Sour Receptor Salty cell Sweet Nerve fiber
LO 3.6 Senses of taste and smell
Taste
Bitter
Taste
pore
Sour
Sensetivity to taste depends on how many taste buds one has. Each taste bud has about 20 receptors. Receive molecules of different substances fit into a receptor like neurotransmitters. Chemical sense.
Receptor
cell
Salty
Sweet
Nerve
fiber
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29. Smell Olfaction (olfactory sense) – sense of smell.
LO 3.6 Senses of taste and smell
Smell
Olfaction (olfactory sense) – sense of smell.
Olfactory bulbs - areas of the brain that receive information from the olfactory receptor cells.
Receptor
Olfactory
bulb
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30. LO 3.7 Touch, pain, motion and balance
Somesthetic Senses
Somesthetic senses - the skin senses, the kinesthetic sense, and the vestibular senses.
Skin senses - the sensations of touch, pressure, temperature, and pain.
Kinesthetic sense - sense of the location of body parts in relation to the ground and each other.
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31. LO 3.7 Touch, pain, motion and balance
Somesthetic Senses
3. Vestibular senses - the sensations of movement, balance
Sensory conflict theory in which the information from the eyes conflicts with the information from the vestibular senses resulting in dizziness.
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32. Perception and Constancies
LO 3.8 Perception and perceptual constancies
Perception and Constancies
Perception - the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion.
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33. Constancy
Size constancy - the tendency to interpret an object as always being the same actual size, regardless of its distance.

34. Constancy
Shape constancy - the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina.

35. Constancy
Brightness constancy – the tendency to perceive the apparent brightness of an object as the same even when the light conditions change.

36. LO 3.9 Gestalt principles of perception
Figure–ground - the tendency to perceive objects as existing on a background.
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37. Gestalt Principals
Reversible figures - visual illusions in which the figure and ground can be reversed.

38. Gestalt Principals

39. Gestalt Principles Similarity Proximity Continuity Closure
LO 3.9 Gestalt principles of perception
Gestalt Principles
Similarity
Proximity
Continuity
Closure
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40. Development of Perception
LO Perceiving the world in three dimensions
Development of Perception
Depth perception - the ability to perceive the world in three dimensions
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41. LO 3.10 Perceiving the world in three dimensions
Monocular Cues
Monocular cues (pictorial depth cues) – cues for perceiving depth based on one eye only.
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42. Monocular cues Linear Perspective Texture gradient Relative size
LO Perceiving the world in
three dimensions
Monocular cues
Linear Perspective
Texture gradient
Relative size
Areal perspective

43. Binocular Cues
Binocular cues - cues for perceiving depth based on both eyes.
Convergence - the rotation of the two eyes to focus on a single object, resulting in greater convergence for closer objects and lesser convergence if objects are distant.
Focal
point
Left
Right
Far
Near

44. Binocular Cues
Binocular disparity - the difference in images between the two eyes, which is greater for objects that are close and smaller for distant objects.

45. LO Visual illusions
Perceptual Illusions
Müller-Lyer illusion

46. LO Visual illusions
Perceptual Illusions
Moon Illusion

47. Perceptual Illusions Illusions of Motion:
LO 3.11 Visual illusions and other factors influencing perception
Perceptual Illusions
Illusions of Motion:
Stroboscopic motion - seen in motion pictures, in which a rapid series of still pictures will appear to be in motion.

48. Factors that Influence Perception
LO Visual illusions and other factors influencing perception
Factors that Influence Perception
Perceptual expectancy- the tendency to perceive things a certain way because previous experiences or expectations influence those perceptions.