1. Chapter 3: Sensation & Perception
Sensation is when energy is picked up by one (or more) of our senses
Perception is when the brain selects, organizes, and interprets this information
Sensation occurs when a receptor cell in a sense organ is stimulated by energy
Transduction is when physical energy is converted into an electrical charge

2. Sensory Thresholds Psychophysics: testing limits and changes
LO 3.2 Identify sensory threshold theories in applied examples.
Psychophysics: testing limits and changes
An absolute threshold is the smallest amount of energy needed for a person to detect a stimulus 50% of the time
Difference Threshold: minimal difference needed to detect a a stimulus change
The just noticeable difference is the minimum difference between two stimuli needed to detect a difference 50% of the time
There is variability in sensory capabilities between people
There is also variability within people based on varying circumstances, which is known as signal detection theory

3. Figure 3.1 Difference Thresholds
Difference thresholds are relative to the size of the initial stimulus. Adding one teaspoon of sugar to a glass of tea would likely produce a noticeable difference in taste. However, adding that same teaspoon of sugar to an entire pitcher is much less likely to be noticed.

4. Table 3.1 Examples of Weber’s Constants
Sensation
Weber’s Constant
Saltiness of food
20%
Pressure on skin
14.2%
Loudness of sounds
10%
Odor 5%
Heaviness of weights 2%
Brightness of lights
1.6%
Pitch of sounds
0.3%
According to Weber’s Law, each of our senses has a different percentage required to detect a change in a stimulus. Notice how much variation there is between the various senses and even specific aspects within each sense (for example, loudness vs. pitch.)

5. Signal Detection Theory
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6. If I Didn’t Sense It, Was It Really There?
LO 3.3 Differentiate subliminal perception from subliminal persuasion.
Subliminal perception is when sensation falls below the absolute threshold
Subliminal persuasion is when subliminal techniques are used to influence people’s behaviors
Subliminally priming individuals can lead to behavior change, but it is usually short lived
Sensory adaptation occurs when your senses are exposed to an unchanging stimulus and stop registering that stimulus

7. Visual Stimuli and the Eye
LO 3.4 Describe how light travels through various parts of the eye.
Vision is based on the availability of light
Light is energy that is contained within the electromagnetic spectrum
We can describe wavelengths in terms of hue, brightness, and saturation
the electromagnetic spectrum

8. Physical/Perceptual properties of light
© 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E

9. © 2011 The McGraw-Hill Companies, Inc.
Properties of Light
wavelength: distance between peaks
perceived as hue
some wavelengths beyond human sensation
amplitude: height of wave
perceived as brightness
purity: mixture of wavelengths
perceived as saturation
© 2011 The McGraw-Hill Companies, Inc.

10. Figure 4.5 Additive and Subtractive Color Mixing

11. Figure 3.3 Anatomy of the Eye
Aqueous humor: fluid in anterior chamber
Vitreous humor: fluid in back (vitreous) chamber
Sclera: outmost covering of eye (white)
Anterior chamber:
just behind cornea
Video:
Video:

12. The Eye: Retina The retina is a thin membrane at the back of the eye.
The fovea in its center is responsible for acuity.
Light hits two types of sense receptors on the retina—rods and cones.
Rods
Peripherally located
Sensitive but colorblind
function well in low illumination
humans have ≈ 120 million rods
Cones
Centrally located (fovea)
respond to color
operate best under high illumination
humans have ≈ 6 million cones

13. The optic nerve carries the neural messages from the eye to the brain to be processed
Because of contralateral control, the right half of each retina processes information from the left visual field and vice versa

14. Figure 4.8 Perception and the Visual Cortex

15. Color Vision Trichromatic theory Opponent-Process theory
LO 3.6 Distinguish the major theories of color vision.
Our brain transduces the sensations from light into the perception of color
The trichromatic theory of color vision states there are three different cones that are each sensitive to varying wavelengths of light
The opponent-process theory states there are three special visual receptors that work in pairs and in an opposing manner (color vision past retina, in thalamus, visual cortex)
Trichromatic theory
Eye contains 3 different color sensitive elements
Blue, green or red elements
Trichromatic theory accounts for color mixing of lights.
Opponent-Process theory
Visual system is organized into red-green, blue-yellow and black-white units.
Theory can account for negative color afterimages.
Video:

16. Figure 3.12 The Opponent-Process Theory of Color Vision
As depicted in Figure 3.12, the first receptor may have an excitatory response to blue and an inhibitory response to yellow, or vice versa. The second receptor shown might exhibit an excitatory response to green and inhibitory response to red. Finally, the third receptor may have an excitatory response to white light and an inhibitory response to black, or the absence of light (De Valois, 1960). The presence of opposing neurons adequately explains negative afterimages.
Video:

17. Auditory Stimuli and the Ear
LO 3.7 Label the anatomy of the ear.
Sound is simply vibration traveling through a medium (usually air) and has
Pitch—wave frequency (Hz)
Loudness—amplitude of the sound waves (dB)
Timbre—complexity of sound
Like light waves, sound waves have wavelength, amplitude, and purity
Frequency is the rate of a sound wave measured in hertz (Hz) and determines the pitch of a sound
The human ear is able to hear sounds that range from 20 to 20,000 Hz
The location of our ears enables us to hear stereophonically, and our heads cast a sound shadow

18. Figure 3.13 Anatomy of the Ear
Video:

19. Cross-section of cochlea
© 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E

20. The Structure and Function of the Ear
The outer, middle, and inner ear do different jobs to transduce sound into neural activity.
The outer ear (pinna and ear canal) tunnels sound waves onto the eardrum.
On the other side of the eardrum, the ossicles (hammer, anvil, stirrup) vibrate and transmit sound to the inner ear.
In the inner ear, the cochlea converts vibration into neural activity.
The organ of Corti and basilar membrane convert auditory information into action potentials.

21. Theories of Hearing
Place theory states that pitches activate different sets of hair cells along the cochlea’s basilar membrane (explains higher-pitch perception)
Frequency theory states that lower-pitched sounds are perceived based on the frequency with which the neurons fire
Volley principle states that neurons take turns firing to create a more complicated neural signal

22. Theories of Hearing (2 of 2)
LO 3.8 Describe the different theories of hearing and types of hearing impairment.
Sensorineural hearing loss results from damage to the cochlea or nerve pathways from the inner ear to the brain
Conductive hearing loss results from the sound not being conducted properly through the outer or middle ear
Mixed hearing loss involves both sensorineural and conductive hearing loss
Video:

23. The Relationship Between Smell and Taste (1 of 2)
LO 3.9 Explain how the senses of smell and taste work together.
Olfaction is a chemical sense in which molecules of a substance are carried to the receptor cells at the top of our nasal cavities
Dogs possess at least 300 million scent receptors compared to 5 million for humans
Olfactory cells regenerate throughout the life cycle
Smell signals don’t travel through the thalamus; they have direct links to the brain’s emotion and memory centers
Video:

24. The Relationship Between Smell and Taste (2 of 2)
Taste: also a chemical sense activated by substances dissolved in saliva
Taste buds are taste receptor cells located in the papillae on the tongue
Our inclination to avoid bitter-tasting foods developed as a defense mechanism against poisonous plants
There are five basic tastes: sweet, salty, sour, bitter, and umami
People with higher densities of taste buds are called “supertasters” and may avoid eating-high fat, high-sugar foods, fruits, and vegetables.
Video:
Video:

25. Figure Smell and Taste

26. Theories of Perception
LO 3.11 Distinguish top-down from bottom-up processing.
Bottom-up processing refers to the type of processing of information that starts with the raw data, or the stimuli from the environment
Top-down processing is sometimes called knowledge- based processing because it relies heavily on your previous knowledge and experience to influence perceptions

27. Form Perception: Gestalt Principles
Source: Based on psychologists Max Wetheimer, Wolfgang Kohler, and Kurt Koffka

28. Perceptual Constancies and Perceptual Sets
LO 3.12 Recognize how perceptual constancies and perceptual sets help to organize sensations and guide perception.
Perceptual constancy – the perception of a stimulus remains the same even though some of its characteristics may have changed
Size constancy – the perception of an object’s size doesn’t change, regardless of changes in distance
Color constancy – recognizing that the color of an object doesn’t change even though the reflected wavelengths of light change in different environments

29. Figure 3.14 Shape Constancy
Objects are perceived as the same shape even though the retinal image may change as a result of different viewpoints.

30. Huffman: PSYCHOLOGY IN ACTION, 7E
Size Constancy
© 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E

31. The Checker-Shadow Illusion: Lightness or Color Constancy
Source: © 1995 Edward H. Adelson

32. Perceptual Hypotheses (6 of 7) LO 4
Perceptual Hypotheses (6 of 7) LO 4.6b Describe how we perceive people, objects, and sounds in our environment.
Depth perception
Monocular depth cues rely on one eye.
Relative size, texture gradient, interposition, linear perspective, height in plane, light and shadow
Binocular depth cues require both eyes.
Binocular disparity and binocular convergence

33. Huffman: PSYCHOLOGY IN ACTION, 7E
Monocular Cues
© 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E

34. Huffman: PSYCHOLOGY IN ACTION, 7E
Retinal Disparity
© 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E