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
• 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
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
Aqueous humor
Vitreous humor
– Cones
– Rods
• Fovea
• Optic Nerve
• Blind Spot/ Optic Disc
Figure: Major Structures of the Eye
Figure: The Lens and the Retinal
How the Eye Works
Left and Right Visual Fields
Areas of the Retinas
Where the information goes
Optic chiasm
– 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
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
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
• 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
• 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
• 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
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
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
Aerial Perspective
Texture gradient
Depth Perception
• Binocular Cues
– Convergence
– Binocular Disparity
Perceptual Illusions
Hermann Grid
Muller-Lyer Illusion
The Moon Illusion
Illusions of motion
Hermann Grid
Muller- Lyer
Other factors that Influence
• 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
• 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.

Sensation and Perception - Shannon Deets Counseling