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 Univ. of Tenn. study found that 60% of college students suffer some high-frequency hearing loss

Loud music: the culpritLive 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

TouchSkin Sensations

★ pressureonly 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

PainGate-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.

PainPain 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

TasteTaste Sensations

sweetsoursaltybitter

Sensory Interaction★ the principle that one

sense may influence another

★ as when the smell of food influences its taste

TasteSome 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

Receptor cells inolfactory membrane

Nasal passage

Olfactorybulb

Olfactorynerve