PSYCHOLOGY – Ms. Shirley
Unit 2 - Sensation & Perception:
Hearing, Touch, Taste & Smell
If a tree falls in the forest... & no one
is around to hear it... does it make a
sound?
"If a tree falls in a forest and no one is around to hear it, does it make a
sound?"
Philosophical thought experiment that raises questions
regarding observation & knowledge of reality.
What is the difference between what something is, & how it appears?
"sound is the variation of pressure that propagates through matter as a wave"
If a tree exists outside of perception then there is no way
for us to know that the tree exists.
So then, what do we mean by 'existence', what is the
difference between perception & reality?
Also, people may also say, if the tree exists outside of perception (as common sense
would dictate), then it will produce sound waves. However, these sound waves will
not actually sound like anything. Sound as it is mechanically understood will occur,
but sound as it is understood by sensation will not occur.
So then, how is it known that 'sound as it is mechanically
understood' will occur if that sound is not perceived?
Frequency (pitch):
Dimension of frequency determined
by wavelength of sound.
★ Measured in hertz (Hz).
★ Humans can hear sounds at frequencies from
20Hz to 20,0000 Hz. (we hear best at around 3,000 to
4,000 Hz, where human speech is centered)
★ Number of complete wavelengths that pass
through point at a given time. This determines
the pitch of a sound.
To human ears, a dog whistle makes only a
quiet hissing sound. The advantage of the dog
whistle is that it doesn't produce a loud irritating
noise for humans that a normal whistle would
produce, so it can be used to train or command
animals without disturbing nearby people.
Intensity (loudness):
Amount of energy in a wave
determined by amplitude relates
to perceived loudness.
★ Loudness is measured in decibels.
★ Amplitude is how loud the sound is.
★ Higher the crest of the wave is the
louder the sound.
Recent U of Tenn. study found that 60%
of college students suffer some highfrequency hearing loss
Loud music: the culprit
Live concerts—120 + decibels, louder
than jack hammer, chainsaw
OSHA: 85 decibels (food processor) 8
hours, 5 days a week will eventually
cause permanent hearing loss
For each 5 decibel increase, the time it
takes to cause lasting injury drops by 1/2
Test: hold finger up as if taking a
courtroom oath, rub thumb, finger
together & should hear a screeching
sound if not, MAY have hearing loss
How do we
perceive
differences in
pitch?
1. Place Theory (Helmholtz)
★ Links the pitch we hear with the
place where the cochlea’s
membrane is stimulated.
★ We hear different pitches because
different sound waves trigger
activity at different places along the
cochlea’s basilar membrane.
2. Frequency Theory
★ The rate of nerve impulses traveling up the
auditory nerve matches the frequency of a
tone, thus enabling us to sense its pitch.
★ We sense pitch by the basilar membrane
vibration at the same rate as the sound.
★ But this theory has trouble explaining high
pitch sounds because our hairs cannot
vibrate at certain speeds. This problem can be
explained using the volley principle.
Why do we have 2 ears?
Auditory Localization
★ Locating a sound in space
★ Depth or distance (analogous to vision)
Auditory Localization
★ Locating a sound in space
★ Depth or distance (analogous to vision)
Hearing loss & Deafness
Conduction Hearing Loss:
Caused by damage to
mechanical system of ear.
*hearing aids can help*
Sensorineural hearing loss:
Caused by damage to cochlea’s
receptor cells or to auditory
nerves.
*hearing aids can NOT help*
YouTube: Derek Coleman Duracell Commercial
Touch
Skin Sensations
★ pressure
only skin sensation with
identifiable receptors
★ warmth
★ cold
★ pain
Pain
Gate-Control Theory
★ spinal cord contains a neurological
“gate” that blocks pain signals or
allows them to pass on to the brain
★ “gate” opened by the activity of pain
signals traveling up small nerve
fibers
★ “gate” closed by activity in larger
fibers or by information coming from
the brain
Pain
Gate-Control Theory
★ Ronald Melzack & Patrick Wall during the
early 1960s, suggests that the spinal cord
contains a neurological "gate" that either
blocks pain signals or allows them to
continue on to the brain.
★ Unlike an actual gate, which
opens and closes to allow things
to pass through, the "gate" in
the spinal cord operates by
differentiating between the
types of fibers carrying pain
signals.
★ Pain signals traveling via small nerve fibers
are allowed to pass through, while signals
sent by large nerve fibers are blocked.
Gate control theory is often used to explain
phantom or chronic pain.
Pain
Pain is an important signal to
our bodies
★ Chronic pain—est. that over
100 million people suffer from
this
○ 1 study had teenaged burn patients
undergo a few minutes of wound
treatment while they played
Nintendo—the patients felt less
pain and spent less time
thinking about their pain in
virtual reality than Nintendo due
to concept of “presences”—
illusion of going inside another
world.
★ Pain requires attention
Taste
Taste Sensations
sweet
sour
salty
bitter
Sensory Interaction
★ the principle that one sense
may influence another
★ as when the smell of food
influences its taste
Taste
Some taste sensations are genetically
programmed: sweetness.
Also, finding bitter and sour foods
unpleasant.
A study of babies had sweet eliciting
smiles, lip smacking, and sour eliciting
protrusion of tongue
These reactions make good evolutionary
sense
Animals tend to be neophobic, and human
children are reluctant to try new things.
One experiment asked a group of subjects
to taste two groups of food (that were the
same). When the items were accurately
named (chopped tomatoes, oatmeal,
beefsteak) more willing them when given
novel names (pendula fruit, lat, langua steak)
However, as true with other stimuli, mere
exposure makes us like them more.
Smell
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane