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Chapter 3. Sensation and Perception. Questions We Will Be Addressing in This Chapter. What is the difference between sensation and perception? How does information from my eyes and ears get to my brain? Why do some people need eyeglasses? How would my voice sound on the moon?

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Chapter 3

Chapter 3

Sensation and Perception


Questions we will be addressing in this chapter
Questions We Will Be Addressingin This Chapter

What is the difference between sensation and perception?

How does information from my eyes and ears get to my brain?

Why do some people need eyeglasses?

How would my voice sound on the moon?

Why can’t I taste anything when I have a cold?


Questions we will be addressing in this chapter cont d
Questions We Will Be Addressing in This Chapter (cont’d)

Which is the largest organ in my body?

How do sensations become perceptions?

What determines how I perceive my world?

How do I recognize familiar people?

Can you “run out” of attention?


Sensing and perceiving the world

Sensing and Perceiving the World

What is the difference between sensation and perception?


Sensation vs perception
Sensation vs. Perception

Sense: A system that translates outside information into nervous system activity.

“Sensations”

Perception: The process of making sensations into meaningful experiences.


Figure 3 1 what do you see
Figure 3.1: What Do You See?


Sensory systems

Sensory Systems

How does information from my eyes and ears get to my brain?


Sensory systems1
Sensory Systems

Accessory Structure – structures that modify stimulus, e.g., outer part of ear

Transduction – process of converting incoming physical energy into neural activity

Receptors – specialized cells that detect certain forms of energy

Adaptation – decreasing responsiveness to stimulus over time


Figure 3 2 elements of a sensory system
Figure 3.2: Elements of a Sensory System


Coding sensations
Coding Sensations

The absolute threshold

Why does an “absolute” threshold vary?

Internal noise

Response criterion


Figure 3 3 the absolute threshold
Figure 3.3: The Absolute Threshold


Signal detection theory
Signal-Detection Theory

What determines a person’s report of a near-threshold stimulus?

Sensitivity is influenced by:

Internal noise

Stimulus intensity

Capacity of the sensory system

Response criterion is one’s internal rule

“Bias”


Judging differences between stimuli
Judging Differences Between Stimuli

Weber’s Law

Just-Noticeable Difference (JND)

“Difference Threshold”


Figure 3 4 the dimensions of a wave
Figure 3.4: The Dimensions of a Wave


Seeing

Seeing

Why do some people need eyeglasses?


Light
Light

Form of energy known as electromagnetic radiation

Visible light – just a tiny slice of electromagnetic radiation (400-750 nanometers)

Light intensity – physical dimension of light waves; how much energy the light contains that determines its brightness

Light wavelengths –refers to length of light wave and produces sensation of color


Figure 3 5 the spectrum of electromagnetic energy
Figure 3.5: The Spectrum of Electromagnetic Energy


Figure 3 6 major structures of the eye
Figure 3.6: Major Structures of the Eye


Figure 3 7 the lens and the retinal image
Figure 3.7: The Lens and the Retinal Image


Converting light into images
Converting Light Into Images

  • Photoreceptors – specialized cells in the retina that convert light energy into neural activity

    • Rods

    • Cones



Seeing color
Seeing Color

Hue – the essential color determined by dominant wavelength of a light

Saturation – purity of a color

Brightness – overall intensity of the wavelengths making up light


Figure 3 9 the color circle
Figure 3.9: The Color Circle


Trichromatic theory of color vision
Trichromatic Theory of Color Vision

Any color can be produced by mixing pure versions of blue, green, and red light

Three types of cones

Short-wavelength cones

Medium-wavelength cones

Long-wavelength cones

Theory cannot explain afterimages


Opponent process theory of color vision
Opponent-Process Theory of Color Vision

Color-sensitive visual elements in the eye are arranged in three kinds of pairs.

Red or green, blue or yellow, black or white

Members of each pair oppose, or inhibit, each other.

When one member of the pair is no longer stimulated, the other is activated.



Hearing

Hearing

How would my voice sound on the moon?


Sound
Sound

The repeated fluctuation – rising and falling – in the pressure of a substance, -e.g., air


Psychological dimensions of sound
Psychological Dimensions of Sound

Loudness

Determined by amplitude of sound wave

Examples

Pitch

Determined by frequency of sound wave

Timbre

Determined by complex wave patterns added to the fundamental frequency of sound


Table 3 2 intensity of sound sources
Table 3.2: Intensity of Sound Sources


Figure 3 13 sound waves and waveforms
Figure 3.13: Sound Waves and Waveforms


Figure 3 14 structures of the ear
Figure 3.14: Structures of the Ear


Figure 3 15 the cochlea
Figure 3.15: The Cochlea




Video cochlea and ringtones
VIDEO: Cochlea and Ringtones

Discussion Questions


Deafness
Deafness

Conduction deafness

Nerve deafness


Auditory pathways to the brain
Auditory Pathways to the Brain

Auditory nerve conveys information to the thalamus which then relays it.

Thalamus relays the information to the primary auditory cortex

Cells in the auditory cortex have preferred frequencies.

Auditory cortex also receives information from other senses.


Coding sounds
Coding Sounds

Place Theory

Cannot explain encoding of very low frequencies.

Frequency Matching Theory

Also called Volley Theory


The chemical senses taste and smell

The Chemical Senses:Taste and Smell

Why can’t I taste anything when I have a cold?


Why chemical senses
Why “Chemical” Senses?

Senses arise from the interaction of chemicals and receptors.

Smell detects airborne chemicals.

Taste detects chemicals in solution coming into contact with receptors inside the mouth.


Smell taste and flavor
Smell, Taste, and Flavor

Smell and taste act as two components of a single system, known as flavor.

Scent and taste pathways converge in the cerebral cortex.

Both tastes and odors prompt strong emotional responses.

Variations in nutritional state affects:

One’s experience of taste and flavor.

One’s motivation to eat particular foods.


Our sense of smell
Our Sense of Smell

Unique relationship between smell and memory.

Species variability in sensitivity to odor and dependency on smell for survival.

E.g., humans have about 9 million olfactory neurons while dogs have 225 million.

Many species have an accessory olfactory system that detects pheromones.


Figure 3 16 the olfactory system
Figure 3.16: The Olfactory System


Sensing your body

Sensing Your Body

Which is the largest organ in my body?


Somatic senses
Somatic Senses

Senses not located in a specific organ but rather spread throughout the body.

Cutaneous senses – include skins senses of touch, temperature, and pain.

Kinesthesia perception – tells brain where parts of the body are; closely related to balance


Sense of touch
Sense of Touch

Important for survival.

Skin is the body’s largest organ

Covers nearly two square yards of surface area.

Weighs more than 20 pounds.

Has hair virtually everywhere on it.


Encoding and adapting to touch information
Encoding and Adapting to Touch Information

Two aspects of an object contacting the skin are encoded.

Intensity is coded by both individual firing rate as well as the number of neurons stimulated.

The location of the nerves stimulated allows the brain to “know” where the touch occurred.

Detection of changes in touch provide most important sensory information.


Sensing temperature
Sensing Temperature

Some of the skin’s sensory neurons respond to temperature changes only.

“Warm” and “cold” fibers

But many fibers respond to both touch and temperature.

These sensations sometimes interact.


Pain as an information sense
Pain as an Information Sense

Pain receptors are free nerve endings.

Two types of nerve fibers carry pain signals from skin to the spinal chord:

A-delta fibers carry sharp, pricking pain sensations.

C-fibers carry continuous, dull aches and burning sensations.

Emotional response influences experience of pain.


Modulating pain
Modulating Pain

Gate Control Theory

A “gate” in the spinal chord either allows or stops pain signals from reaching the brain.

The brain can also block incoming pain signals.

Natural analgesic systems

Endorphins

Thinking Critically – Acupuncture


Sensing body position
Sensing Body Position

Proprioception – sensory systems that tell us about the location of our body parts and what each is doing


Proprioceptive sensory systems
Proprioceptive Sensory Systems

Kinesthesia

Tells us where the parts of our body are in relation to one another.

Information primarily comes from the joints and muscles.

Vestibular Sense

Tells the brain about the position of the head and about its general movements.

Often referred to as the sense of balance.


Perception

Perception

How do sensations become perceptions?


Figure 3 19 misperceiving reality
Figure 3.19: Misperceiving Reality

Which Line Is Longer?


Organizing the perceptual world

Organizing the Perceptual World

What determines how I perceive my world?


Two basic principles
Two Basic Principles

  • Figure-ground Perception

    • Figure – part of visual field with meaning

    • Ground – contourless part of visual field; background

  • Grouping


Figure 3 20 reversible images
Figure 3.20: Reversible Images


Grouping principles
Grouping Principles

Proximity

Similarity

Continuity

Closure

Texture

Simplicity

Common fate

Synchrony

Common region

Connectedness


Figure 3 21 gestalt principles of perceptual grouping
Figure 3.21: Gestalt Principles of Perceptual Grouping


Stimulus cues for depth perception
Stimulus Cues for Depth Perception

Interposition

Relative Size

Height in the Visual Field

Convergence

Linear Perspective

Reduced Clarity

Light and Shadow

Gradient


Cues based on properties of the visual system
Cues Based on Propertiesof the Visual System

Accommodation

Convergence

Binocular disparity


Perception of motion
Perception of Motion

Optical flow cues

Looming

Role of vestibular and touch senses

Stroboscopic motion


Perceptual constancy
Perceptual Constancy

Size constancy

Shape constancy

Brightness constancy


Figure 3 25a optical illusions
Figure 3.25a: Optical Illusions


Figure 3 25b optical illusions
Figure 3.25b: Optical Illusions


Figure 3 25c optical illusions
Figure 3.25c: Optical Illusions



Recognizing the perceptual world

Recognizing the Perceptual World

How do I recognize familiar people?


How does recognition occur
How Does Recognition Occur?

Bottom-Up Processing

Basic information units that serve as foundation for recognition

Top-Down Processing

Higher-level cognitive processes

Psychological factors, such as expectations

Linkages – Perception and Human Development


Figure 3 26 categorizing perceptions
Figure 3.26: Categorizing Perceptions

What do you see here?

What do you see here?


Figure 3 27 another version of figure 3 26
Figure 3.27: Another Version of Figure 3.26

Now do you see the dog?

Now do you see the dog?


Figure 3 28 interaction of top down and bottom up processing
Figure 3.28: Interaction of Top-Down and Bottom-Up Processing


Figure 3 29 culture and depth cues
Figure 3.29: Culture and Depth Cues

Which animal is closer to the hunter?The elephant or the antelope?


Attention

Attention

Can you run out of attention?


What does attention allow us to do
What Does Attention Allow Us to Do?

Direct our sensory and perceptual systems toward certain stimuli.

Select specific information for further processing.

Allocate the mental energy required to do that processing.

Regulate the flow of resources necessary for performing a task or coordinating several tasks at once.


Characteristics of attention
Characteristics of Attention

Attention improves mental processing.

Attention takes effort.

Attention is limited.

Focus on Research: Attention and the Brain


Directing attention
Directing Attention

Overt vs. covert orienting

How can we control or allocate attention?

Voluntary control

Involuntary control

Inattentional blindness

Parallel processing

Difficulty sometimes with keeping attention focused rather than divided


Fig. 3.33: The Stroop Task: Name the color of the INK in which each word is printed as rapidly as you can…



Thinking critically does acupuncture relieve pain
Thinking Critically: Does Acupuncture Relieve Pain?

What am I being asked to believe or accept?

Twirling needles in the skin can relieve pain caused by everything from tooth extraction to cancer.

Is there evidence available to support the claim?

PET and MRI studies.

Studies showing positive results in 50-80% of patients treated by acupuncture for various kinds of pain.

Contradictory results as well.

Similar pain relief produced by drugs that slow the breakdown of opiates.

Continue to next slide


Thinking critically does acupuncture relieve pain cont d
Thinking Critically: Does Acupuncture Relieve Pain? (cont’d)

Can that evidence be interpreted another way?

Body’s painkilling system can be stimulated by external means such as acupuncture.

What evidence would help to evaluate the alternatives?

More placebo-controlled studies

Difficulty with doing double-blind studies

Continue to next slide


Thinking critically does acupuncture relieve pain cont d1
Thinking Critically: Does Acupuncture Relieve Pain? (cont’d)

What conclusions are most reasonable?

Acupuncture does relieve pain and reduce nausea but not a cure-all.

Acceptance of acupuncture will depend on the quality of future studies.

Return to main slide


Focus on research attention and the brain
Focus on Research:Attention and the Brain

What was the researchers’ question?

Does information-processing activity in the brain slow down when we direct attention to more than one task?

How did the researchers answer the question?

Examined the brain processing speed of participants engaged in various tasks.

Continue to next slide


Focus on research attention and the brain cont d
Focus on Research:Attention and the Brain (cont’d)

What did the researchers find?

Reaction times slowed down when attention had to be shared.

What do the results mean?

Information-processing in the brain was slower.

Further support provided by PET scans.

Continue to next slide


Focus on research attention and the brain cont d1
Focus on Research:Attention and the Brain (cont’d)

What do we still need to know?

What are the limits of attention and processing?

How is attention shared?

What specific parts of the brain are involved in attention?

Return to main slide


Linkages perception and human development
Linkages: Perception and Human Development

What perceptual abilities are we born with?

Studied using the habituation/dishabituation technique

Are we born with the ability to combine features into perceptions of whole objects?

Ability to accurately perceive depth and distance develops more slowly

Return to main slide


Relative SizeThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


InterpositionThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


Linear PerspectiveThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


Relative ClarityThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


Texture GradientThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


ShadowingThis image is missing a monocular depth cue. Please click on the image to reveal the depth cue.

Return to Slide


Cochlea and ringtones video discussion questions
Cochlea and Ringtones Video: Discussion Questions

Return to main slide

This “ringtone” sound was originally implemented to keep kids away from convenience stores. Do you feel such targeted use of technology is fair? Why or why not?

Does such a marked difference between adult and child hearing capacity surprise you? Why or why not?

In what other ways might our senses be eroded over time? How much of it is natural? How much of it is of our own doing?

Will this video make you question the sounds you expose yourself to—or are exposed to—in your environment?


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