Chapter 5- Sensation
Day 1
Sensation vs. Perception
Sensation: a process by which our sensory receptors and nervous system receive and
represent stimulus energy
Sensation is the raw data our brain takes in from the environment.
Perception: a process of organizing and interpreting sensory information, enabling us
to recognize meaningful objects and events.
Perception “makes sense” of sensation.
Example: Prosopagnosia
Bottom Up vs. Top Down Processing
Bottom Up Processing: analysis that begins with the sense receptors and works up to
the brain’s integration of sensory information.

Top Down Processing: Information processing guided by higher-level mental
processes
As when we construct perceptions drawing on our experience and
expectations.

Psychophysics
Psychophysics: study of the relationship between physical characteristics of stimuli
and our psychological experience of them
LightSoundPressureTasteSensation: Thresholds
Absolute Threshold:
Usually defined as the stimulus needed for detection 50% of the time.
“Subliminal Messages”
Subliminal: information that is below one’s awareness for conscious attention

Difference Threshold or (JND-Just Noticeable Difference): the minimum
difference that a person can detect between two stimuli.
Weber’s Law: to perceive a difference between two stimuli, they must differ by a
constant proportion
light intensityweighttone frequencySignal Detection Theory: predicts how and when we detect the presence of a faint
stimulus (signal) amid background stimulation (noise)
Assumes that there is no single absolute threshold
Sensory Adaptation
Sensory Adaptation: diminished sensitivity with constant stimulation.
The Science of Energy and Sensation
TransductionWavelength H ue -
Intensitybrightness
loudness
Day 2
Sense 1- vision
Biology of Vision Step One: Light Enters the Eye
1.) Light enters the eye through the _____________: (transparent protector) and
the light passes through the _______________: (small opening/hole). The
size of the opening (pupil) is regulated by the ____________: the colored
portion of your eye that is a muscular tissue which widens or constricts the
pupil causing either more or less light to get in.
Biology of Vision Step Two: An Image is Produced
2.) Behind the pupil, the ___________, a transparent structure, changes its
curvature in a process called _________________, and focuses the light rays
into an image on the light-sensitive back surface called the __________: where
image is focuses.
Biology of Vision Step Three: Chemical Reactions and Sight
3.) Image coming through activates photoreceptors in the retina called
__________________. As rods and cones set off chemical reactions they form
a synapse with _________________ which forms a synapse with
______________ which fire action potentials along the _______________: that
carries this information to be processed by the ________________: (sensory
switchboard) that sends information to the ___________________ which
resides in the ___________________. The brain then constructs what you are
seeing and turns image right side up.
Parts of Retina
Blind Spot: part of retina where optic nerve leaves the eye…no receptor cells are
there.
Fovea: central focal point of the retina, where cones cluster.
Cones: located near center of retina (fovea)
fine detail and color vision
Rods: located near peripheral retina
detect black, white and gray
Errors In Vision
Acuity:
Nearsightedness:
nearby objects seen more clearly
Farsightedness:
faraway objects seen more clearly
Visual Involves Parallel Processing
Parallel vs. Serial: parallel means simultaneous while serial means step by step. Our
brains process are often parallel processes while computers work serially.
Parallel Processing: simultaneous processing of several dimensions through multiple
pathways. Different part of brain for:
Parallel Processing
Feature Detectors: neurons in the visual cortex respond to specific features
Visual Information Processing
Trichromatic (three color) Theory
Young and Helmholtz
three different retinal color receptors
Color Deficient Syndrome
People who suffer red-green blindness have trouble perceiving the number within the
design
Opponent-Process Theory- opposing retinal processes enable color vision.
Color Constancy
Human Beings maintain Color Constancy: perceiving familiar objects as having
consistent color, even if lighting changes to alter the wavelength given off by the
object.
Context Affects Color
We only retain color constancy when the context remains the same.
Same color will look different when compared in different contexts.
Day 3
Sense 2: Hearing (Audition)
The loudness of a sound is determined by a waves amplitude (height.)
The frequency, number of complete wavelengths that pass a point in a given time,
determines the sounds pitch:
Hearing Threshold
Hearing is measured in decibels.
Parts of the Ear
Outer Ear:
Job:
Parts: auditory canal and eardrum.
Middle Ear
Job:
Parts: Ossicles, made up of three tiny bones: hammer, anvil, and stirrup
(malleus, incus, and stapes)
Inner Ear
Job:
Parts: Oval Window, Cochlea, Basilar Membrane, Hair Cells.
Process of Hearing
1.Your ______________________________________________________________.
2.Your _________________________ with sound waves
3.This causes _________________________________ (the hammer, anvil and the
stirrup) ____________________________________________________
4. ______________________________________________________________. The
cochlea is fluid filled and _____________________________.
5. Inside the cochlea is a ____________________________________________ and
are transduced into a _____________________________
6. Hair cells synapse with _______________________________________________
7. The auditory nerve transmits sound messages though your ____________________
____________________________________________________________________
Inner Ear and Vestibular Sense
The semicircular canals are connected to the cochlea by the vestibular sacs.
The semicircular canals contain substance that move when our head rotates or tilts
and allows us to maintain our vestibular sense.
How Do We Perceive Pitch: 2 Theories
Hemholtz’s Place Theory: argues we hear different pitches because different
sound waves trigger activity at different places in the cochlea’s membrane
Frequency Theory: We sense pitch by the basilar membrane in cochlea vibrating at
the same rate as the sound. Explains low pitch well….
Volley PrincipleParallel Processing
Just like with vision, audition involves parallel processing
Hearing Loss
Conductive Hearing Loss: hearing loss caused by damage to the mechanical system
that conducts sound waves to the cochlea like eardrum and ossicles.
Sensorineural Hearing Loss: damage caused to cochlea’s receptor cells (hair cells) or
auditory nerves.
Day 4
Sense 3-Touch
Premature Babies
Monkeys
Skin sensations are a variation of the basic 4
Pain Is a Good Thing!
Gate Control Theory:
Social Influence On Pain
-Pain is both a physiological and a psychological phenomenon.
-Depending on symptoms, doctors may use drugs, surgery, etc. or relaxation training,
thought distraction.
Example:
Memories of Pain
More to our memories of pain than the pain we experienced.
People tend to overlook duration of pain and instead concentrate on its peak moments
and how much pain they felt at the end.
Sense 4-Taste
4 Basic Sensations
Sweet
Sour
Salty
Bitter
Taste and Smell
Taste and Smell are both chemical senses.
Tongue is central muscle for taste which contain taste buds.
Smell runs through receptor cells in nasal cavity which are send neural signals to the
olfactory bulbs in the brain.
Sense 5-Smell
5 million receptor cells at the top of your nasal cavity
Detect 10,000 odors
Decreases with age
Nasal Cavity brings the smell up to your receptors
Receptor cells send the message to the brain’s olfactory bulb,then to the temporal
lobe’s primary smell cortex
Smell and Emotion
Sense of smell activates areas in limbic system involved in emotion and memory.
Smells can often evoke memories of the past or emotional experiences more often
than most other senses.
Sensory Restriction
People born without access to a sense, compensate with development of stronger
other senses.
Sensory Restriction has produced mixed results depending on context: