copyright © houghton mifflin company. all rights reserved. 3–13–1 chapter three sensation and...

Copyright © Houghton Mifflin Company. All rights reserved. 3–1

Chapter Three

Sensation and Perception


Did You Know That…

• Our sense of smell may not be as keen as that of dogs, but humans can detect the presence of even one drop of perfume dispersed through a small house?

• Roy G. Biv is one of the most famous names learned by psychology students, but he is not a real person?

• Listening to music on a “Walkman” or similar device can permanently damage your hearing?


Did You Know That… (cont.)

• Salmon use the sense of smell to sniff out the streams of their birth when they return to spawn?

• Some people are born with a distaste for broccoli?

• We have a sense that enables us to locate the parts of our body in the dark?


Did You Know That… (cont.)

• Newborn babies prefer the sounds of their mothers’ voices to the voices of other women?

• The mechanism that makes motion pictures possible lies in the viewer, not the projector?


Module 3.1

Sensing Our World: Basic Concepts of Sensation


Module 3.1 Preview Questions

• What is sensation?• What is the difference between absolute

thresholds and difference thresholds?• What factors contribute to signal detection?• What is sensory adaptation?


What Is Sensation?

• The process by which we receive, transform, and process stimuli from the outside world to create sensory experiences of vision, touch, hearing, taste, smell, etc.


Sensory Receptors

• Specialized cells that detect sensory stimuli and convert them into neural impulses.

• Locations of sensory receptors:– Eyes– Ears– Nose– Mouth– Joints, muscles– Skin


Psychophysics

• The study of the relation between the features of physical stimuli and the sensations we experience in response to these stimuli.

• Gustav Theodor Fechner’ (1860) Elements of Psychophysics


Absolute and Difference Thresholds

• Absolute Threshold: Smallest amount of a stimulus that a person can reliably detect.

• Difference Threshold: Minimal differences between two stimuli that people can reliably detect.– Also called “just-noticeable difference” – Weber’s law


Signal Detection

• The theory that the threshold for detecting a signal depends on factors involving:– The intensity of the stimulus,– The level of background stimulation,– The biological and psychological characteristics of

the perceiver.


Sensory Adaptation

• The process by which sensory receptors adapt to constant stimuli by becoming less sensitive to them.

• Adaptation may not occur when repeatedly exposed to certain strong stimuli.


Module 3.2

Vision: Seeing the Light



• How do the eyes process light?• What are feature detectors, and what role do

they play in visual processing?• What are the two major theories of color

vision?• What are the two major forms of color

blindness?


Figure 3.1: The Electromagnetic Spectrum


Figure 3.2: The Color Spectrum


Figure 3.3: Parts of the Eye

Figure 3.5:Light to Neural Impulses


Feature Detectors

• Neurons that respond to specific features of the visual stimulus.

• Visual cortex compiles information from various cells to form meaningful patterns.


Trichromatic Theory of Color Vision

• Thomas Young (1773-1829)

• Hermann von Helmholtz (1821-1894)

• Eyes have 3 types of color receptors or “cones.”– Red, green, blue-violet


Opponent-Process Theory

• Ewald Hering (1834-1918)• Three pairs of opposing color receptors

– Red-Green– Blue-Yellow– Black-White

• When one color is activated, other is inhibited.


Which Theory of Color Vision Is Right?

• Both theories to a certain extent.• Trichromatic theory is correct at receptor

level.• Opponent-process is correct with respect to

behavior of cells that lie between the cones and the occipital lobe.


Color Blindness

• Trichromats: Normal color vision

• Monochromats: No color vision

• Dichromats: Can see some colors but not others


Module 3.3

Hearing: The Music of Sound



• How does the ear enable us to hear sound?• What determines our perception of pitch?• What are the main types and causes of

deafness?


Figure 3.10: Sound Waves


Characteristics of Sound

• Amplitude determines perceived loudness.• Frequency determines perceived pitch.


Figure 3.11: Conversion of Sound Waves into Neural Impulses


Perception of Pitch

• Place Theory: Location of vibration along basilar membrane determines pitch.

• Frequency Theory: Basilar membrane vibrates at same frequency as sound wave.

• Volley Principle: Groups of neurons along basilar membrane fire in rotation.


Figure 3.12: Sounds and Decibels


Hearing Loss

• Conduction Deafness: Damage to middle ear.– May benefit from hearing aids.

• Nerve Deafness: Damage to hair cells of the inner ear or auditory nerve.– Use of cochlear implants sometimes successful.

• Hearing loss largely due to years of abuse from loud music and noise.


Module 3.4

Our Other Senses: Chemical, Skin, and Body Senses



• How do we sense odors and tastes?• What are the skin senses?• What are the kinesthetic and vestibular

senses?


Figure 3.13: Olfaction


Olfaction

• Smell is only sense not to pass through the thalamus.

• Odor preferences seem to be inborn.• Key factor in the flavor of food.

• Serves many other functions in various animal species.


Pheromones

• Chemical substances emitted by many species.

• Pheromones play important roles in many behaviors, including sexual attraction.

• Do pheromones influence human behaviors?


Taste

• Four basic tastes: sweet, sour, salty, bitter

• Flavor derives from: taste, aroma, texture, temperature


Factors Influencing Food Preference

• Cultural background• Genetic factors• Taste sensitivity

– One in 4 are “supertasters”


The Skin Senses

• Largest sensory organ• Codes for sensations of

touch, pressure, warmth, cold, and pain


Gate-Control Theory Of Pain

• Mechanism in spinal cord controls pain messages.

• Bottleneck at the “gate” may block pain.• Role of endorphins in controlling pain

– May explain benefits of acupuncture.


Kinesthesis

• Body sense that provides information about:– Movement of body parts– Relative position of body parts

• Receptors in joints, ligaments, muscles


Vestibular Sense

• Functions:– Monitors position of body

in space– Helps maintain balance

• Conflict with vision = motion sickness


Figure 3.16: Vestibular Sense (Larger View)


Module 3.5

Perceiving Our World: Principles of Perception



• What is perception?• How is perception influenced by attention and

perceptual set?• What are the two general modes of

processing visual stimuli?• What are the Gestalt principles of perceptual

organization?


Module 3.5 Preview Questions (cont.)

• What is perceptual constancy, and what cues do we use to perceive depth and movement?

• What are visual illusions?• Does subliminal perception exist?• Does evidence support the existence of ESP?


Perception

• Process by which the brain interprets sensations, turning them into meaningful representations of the world

• It is an active process.• Perceptions may not accurately reflect

external reality.


Figure 3.17: Perception vs. Reality?


Attention

• Selective Attention: Attention is limited to certain stimuli while other stimuli are filtered out.

• Influenced by:– Motivational states– Repeated exposure

• Constant exposure can lead to habituation.


Perceptual Set

• Perceptions are influenced by expectations, preconceptions.

Is this the Letter B or the Number 13?


Figure 3.19: A Duck or a Rabbit?

Source: © Figure from H.R.Schiffman, Sensation and Perception: An Integrated Approach, pp.190 & 220. Copyright © John Wiley & Sons Inc. Reprinted with permission.


Visual Processing

• Bottom-Up Processing: Focus on specific shapes, individual features

• Top-Down Processing: Experience and knowledge shape perception


Figure and Ground Perception

Reversible Figure Ambiguous Figure


Figure 3.23: Old/Young Woman


Figure 3.24: Gestalt Laws of Grouping


Perceptual Constancies

• The tendency to perceive an object as remaining the same even when retinal image changes.

• Examples– Size constancy– Color constancy– Brightness constancy– Shape constancy


Figure 3.25: Shape Constancy


Binocular Cues for Depth

• Cues for depth that involve both eyes.• Retinal Disparity: Cue for distance based on

the slight differences in the visual impressions formed in both eyes.

• Convergence: Cue for distance based on the degree of tension required to focus two eyes on the same object.


Cues for Motion Perception

• Path of image as it crosses the retina• The changing size of the object


Figure 3.28: Müller-Lyer Illusion and Ponzo Illusion


Figure 3.29: Impossible Figure


Figure 3.30: Moon Illusion


Figure 3.31: Stroboscopic Movement


Phi Phenomenon

• Illusion of movement created by the rapid switching on and off of columns of lights.


Cultural Differences

• Perception influenced by both our sensory systems as well as our cultural experiences.

• Müller-Lyer illusion and the carpentered-world hypothesis

• Ponzo illusion less prominent among people of Guam.


Subliminal Perception

• Stimuli presented below level of conscious awareness.

• Can it influence attitudes or behavior?


Extrasensory Perception

• Perception that occurs without benefit of the known senses.

• Common forms of paranormal phenomena:– Telepathy– Clairvoyance– Precognition – Psychokinesis

• Has not been demonstrated scientifically.


Module 3.6

Application: Psychology and Pain Management


Module 3.6 Preview Question

• What have psychologists learned about controlling pain?


Pain Management

• Distraction• Creating a bottleneck at the “gate”• Changing thoughts and attitudes• Obtaining accurate information• Meditation• Biofeedback

copyright © houghton mifflin company. all rights reserved. 3–13–1 chapter three sensation and...

Documents

perception slide

sensory stimuli

muscles skin slide

sensory adaptation

process stimuli

locations of sensory

sensory experiences

absolute thresholds