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Sensation and Perception
Ciccarelli and White
Chapter 3
Introductory Psychology Spring 2014
Sensation and Perception
• Sense- a system that translates outside
information into activity in the nervous system
• Sensation- the stimulus message coming from
the senses
• Transduction- process of converting stimuli
• Perception- the process of giving meaning to
that message
Figure: What Do You See?
ABC’s of Sensation
• Sensation is the activation of receptors in the various
sense organs
• Sensory Receptors
– Specialized forms of neurons
– Not stimulated by other neurons
– Stimulated directly by different kinds of energy (light waves,
sound waves, etc)
Sensory Energy
• Wavelength- the distance between peaks in a
wave of light and sound
• Frequency- number of complete waves, or
cycles, that pass a given point per unit of time
• Amplitude- the distance between the peak
and the baseline of a wave
Figure: The Dimensions of a Wave
Sensory Systems- How Information
gets from Sensation to Perception
• Your senses gather information through
various forms of energy
• This energy is encoded into neuronal activity
• Neuronal activity relays signals to the brain
Modification of Energy into
Neuronal Activity
• In some sensory systems the first step in sensation
involves modifying the incoming stimulus
– Accessory structures complete this modification
• The second step in modification is transduction
– Transduction is the process of converting incoming energy
into neuronal activity
– Transduction takes place at structures called receptors
Transfer of Information through
CNS
• Coding translates the physical properties of a
stimulus into neural activity
• Sensory nerves transfer coded activity to the
brain (Thalamus)
• Coded information for all senses except smell
goes to the Thalamus
• Thalamus does some initial processing and
sends information to the Cerebral Cortex
• Cortex receives input and produces sensation
and perception
Review of Structures of Forebrain
Review: Elements of a Sensory
System
Sensory Threshold
– Sensory Thresholds
• Weber’s Law of just noticeable differences
– Ex: Sugar in Coffee (20%)
» Already have 5 teaspoons, must add 1 teaspoon
» Already have 10 teaspoons, must add 2 teaspoons
» Coffee regular
• Absolute Threshold
• Subliminal Perception
• Movie
• Habituation and Sensory Adaptation
The Science of Seeing
• The Science of Seeing
– Psychological Properties of Light
• Three psychological aspects to light
– Brightness
– Color
– Saturation
Figure: The Spectrum of
Electromagnetic Energy
Structures of the Eye
– The structure of the eye
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Cornea
Aqueous humor
Iris
Pupil
Lens
Vitreous humor
Retina
– Cones
– Rods
• Fovea
• Optic Nerve
• Blind Spot/ Optic Disc
Figure: Major Structures of the Eye
Figure: The Lens and the Retinal
Image
How the Eye Works
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Left and Right Visual Fields
Areas of the Retinas
Where the information goes
Optic chiasm
Photoreceptors
– Rods
– Dark adaptation
– Light adaptation
– Cones
Color vision
– Color Vision
• Trichromatic Theory
• The Afterimage
• Opponent-process theory
– Lateral geniculate nucleus
• Color Blindness
Perception of Sound
• What is sound
• Properties of sound waves
• Auditory Spectrum
The Structure of the Ear
The structure of the ear
• The outer ear
• The Middle ear
• The inner ear
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Cochlea
Basilar Membrane-resting place of the organ of Corti
Organ of Corti- contains receptor cells for the sense of hearing
Auditory Nerve- bundle of axons from the hair cells in the
inner ear that run to the brain
Figure: Structures of the Ear
Figure: The Cochlea
Perceiving Pitch
– Theories of Pitch
• Pitch- psychological experience of sound that
corresponds to the frequency of the sound waves;
higher frequencies are perceived as higher pitches
• Place Theory
• Frequency Theory
• Volley Principle
Types of Hearing Impairments
– Types of Hearing Impairments
• Conduction Hearing Impairment
– Hearing aids
• Nerve hearing impairment
– Tinnitus
– Cochlear implants
Figure: Sound Waves and
Waveforms
Table: Intensity of Sound Sources
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.
Chemical Senses
• Chemical Senses
– Gustation
• Taste buds
• Five basic tastes
• Supertasters
– Olfaction
• Definitions
• Olfactory receptor cells
• Olfactory bulbs
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.
Figure: The Olfactory System
Olfactory System
• 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.
Somesthetic Senses
– Touch, Pressure, Temperature
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Types of sensory receptors
Visceral pain, somatic pain
Congenital analgesia
Congenital insensitivity to pain with anhidrosis
Phantom limb
Pain Gate Control Theory
Kinesthetic Sense/ Vestibular Sense
– Kinesthetic Sense
– Vestibular Sense
• Otolith organs
• Semicircular canals
• Motion sickness
ABC’s of perception
• The ABC’s of Perception
– Size, Shape, and Brightness
– Gestalt Principles
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Figure-ground
Proximity
Similarity
Closure
Continuity
contiguity
Figure 3.20: Gestalt Principles of
Perceptual Grouping
Depth Perceptions
Monocular Cues
– Linear perspective
– Relative size
– Overlap
– Aerial perspective
– Texture gradient
– Motion parallax
– accommodation
Linear perspective
Relative Size
Overlap
Aerial Perspective
Texture gradient
Depth Perception
• Binocular Cues
– Convergence
– Binocular Disparity
Perceptual Illusions
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Hermann Grid
Muller-Lyer Illusion
The Moon Illusion
Illusions of motion
Hermann Grid
Muller- Lyer
Other factors that Influence
perception
• Perceptual sets
• Top down processing
• Bottom up processing
Figure 3.18: Misperceiving Reality
Which Line Is Longer?
From Gardner "Optical Illusions from Figures that are Undecidable to Hot Dogs That Float, Scientific American, 222, 124, 127 Reprinted with permission
Figure: Reversible Images
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Synesthsia
• Disorder in which the signals from the various
sensory organs are processed in the wrong
cortical areas resulting in the sense
information being interpreted as more than
one sensation.