Sensation

Goals of the day: Thresholds Vision Hearing Other senses

Basic definitions

Sensation: the detection of energy from physical environment and encoding it as neural signals in the brain

Perception: how we select, organize and interpret our sensations

Psychophysics: study of how physical energy relates to psychological experience

Transduction: process of converting physical energy stimuli into neural impulses

Basic elements

Input from the Physical Environment Light waves Sound waves Molecules in the air that carry odors Other physical objects (can touch us)

Receptors Rods and cones, Cochlea, basilar membrane with protruding hair cells Taste buds Olfactory bulbs, Nerve endings on skin

Information processing Centers in Brain where information from sensors

register

How much sugar do you need in your coffee before it tastes sweet?

We perceive things in with regard to intensity (quantity, how much) and quality

Thresholds are related to intensity

Absolute threshold: minimum stimulation needed to detect a stimulus-- where you can detect it at least 50% of the time.

Evolution and threshold differences

One of the first things we notice about sensation are differences in sensation thresholds sense of smell: dog vs. human (bomb sniffing; cancer

sniffing) hearing (dogs) smell (men vs. women) taste - differences between people in perceiving

spiciness in food (children v. adults--ability to detect pepper)

vision: antelope vs. human; bear vs. human

If you put four teaspoons of sugar into your coffee, how many more do you need to add to make it taste sweeter?

Difference threshold: (just noticeable difference, J N D) the minimum difference a person needs to detect a difference between two stimuli at least 50% of the time

The more intense the existing stimulus, the larger the change must be to be noticeable How much much the price of a CD go up

before you notice the difference ($2? ). How about the price of a new car?

Weber’s Law

The difference threshold is a constant proportion of the stimulus Weight, 2% (10 lbs to 10.2 or 100

pounds 102 pounds to notice the difference)

Line length, 1% Tones, 3%

How bad do locker rooms smell?

It depends on how long you are in one

Sensory adaptation: diminishing sensitivity to an unchanging stimulus

Why do things appear black and white when the lights go down?

Rods and cones receptor cells that convert light energy

into neural signals (transduction)Rods: cells that detect black, white and

gray; necessary for peripheral and twilight vision (120 million)

Cones: cells that detect fine detail and color; function well in well-lit conditions (6 million)

Frequency and amplitude

Frequency = wavelength Amplitude = wave height Vision

frequency = color amplitude = brightness

Sound Frequency is to pitch as amplitude is to _____? frequency = pitch amplitude = loudness

Do bees see the same things as we do?

Not completely.Bees detect ultraviolet wavelengths.

We can’t see them.Why?

Different ecological niches of occupied by different species demand different perceptual sensitivities

How is our vision similar to your color TV?

Young-Helmholtz trichromatic (3-color) theory of color vision any color can be created by combining light waves of 3

primary colors (red, green, blue) retina has 3 types of color receptors, each sensitive to: red,

green, blue light color vision works by additive principle (absorbs light) mixing these three colors produces over 1,000 shades of

color

Color blindness lack of functioning red or green sensitive cones; vision is

dichromatic, making it difficult to distinguish red and green

What is more important to a soldier: detecting motion or camouflage? Why

Feature debtors: cortical neurons that respond to specific features of a scene edges, lines, angles, motion detectors, face

detector, grandmother detectorfacial recognition uses 30% of the cortex, 10

times what is used for hearing. why is facial recognition so important?

motion detection. Registers first in the brain Parallel processing

our brains do many things at once, by specialized, overlapping neural networks

The sensation of hearing

Sound: acoustic energy, rhythmic pulsation from vibrating object does tree falling is woods produce

sound if no one is there to hear it? Frequency units = Hz: humans, 15 to

20,000 Hz; dogs 15 to 50,000 Hz Amplitude units = decibels

Theories of sound perception

Place theory We hear different pitches because different sound

waves trigger activity at different places along the cochlea's basilar membrane

The brain recognizes a pitch depending on the place on the membrane from which it receives neural signals

However, this only works with high frequencies; low pitched sounds are not so localizedAs people age, they lose ability to hear high

pitched sounds

Frequency theory Basilar membrane vibrates with the incoming

sound wave. This vibration triggers neural impulses to the brain at the same rates as the sound wave.

The brain reads pitch from the frequency of neural impulses.

This is how we perceive low pitched sounds

Other senses

Proprioceptive (movement and body position) Kinesthesis: system for sensing the

position and movement of the muscles, tendons, and joints

Vestibular sense: position of the body in space by sensing gravity and movement

Smell why do women have a more sensitive

sense of smell than men?Taste

why do we have preferences for particular types of tastes?

Touch is pain a good thing?