Sensation – the process of receiving information
from the environment
“Bottom-up processing” – think of the
sense as the bottom, the beginning of
an experience
Perception – our interpretation of what the incoming
sensory info. means (WHAT WE MAKE OF IT)
“Top-down processing” – complex brain interpretation
(top of the body)
*The first area of psychology studied – called
Psychophysics (by G. Fechner)
Before sensation can take place, sensory
stimulation must meet threshold
Threshold – the amount of stimulation needed to trigger
a neural impulse
Absolute threshold – the minimum amount of stimulation
needed to trigger a neural impulse 50% OF THE TIME
Each of the senses has an established, scientific absolute threshold
**THRESHOLD VARIES, BY PERSON, BY SITUATION
Signal detection – ability to detect a weak stimulus when extra
effort is made
Just Noticeable Difference refers to the amount of change in
the stimulus required before a difference is noticed
Weber’s Law is a mathematical formula for that concept
change in K (value for stimulus)
K
A controversial threshold experience: subliminal
stimulation
Started with an experiment by James Vicary in 1957
The famous “Eat popcorn”, “drink Coca-Cola”
experiment
Vicary admitted it was a hoax before he died!!
Read – sensory adaptation
Transduction – process by which energy is converted into
neural impulse – at the receptor level for each sense
The 5 senses:
1. Vision – the dominant sense
Light – travels in waves, strikes an object, some wavelengths
absorbed, others reflected back – the reflected light is what
we perceive & label
Amplitude =
Properties of light:
height of wave
(intensity of
color)
Wavelength =
Saturation –
frequency(length) of
purity of
wave (hue)
wavelength
ROYGBIV
Structure of the eye:
1. Conjunctiva
2. Cornea
3.
4.
5.
6.
Sclera
Iris
Pupil
Aqueous humor
7. Lens
8. Ciliary muscles &
ligaments
11. Retina
12. Fovea centralis
9. Vitreous humor
13. Blind Spot
14. Optic Nerve
10. Choroid
Receptors in the retina: rods and cones
Cones:
used for color vision
used for daylight vision
located in center of the retina
approx. 7 million each eye
provide sharp, detailed vision
contain photochemicals called OPSINS
Rods:
used for night vision
used for white and black
heavily packed into the peripheral area of retina
approx. 120 million each eye
provide rough outlines of shapes
4 + layers of cells
process neural
impulse
4 layers from
rods/cones –
bipolar, amacrine,
horizontal and
ganglion cells
H
B
A
G
Theories of color vision:
1. Tri-chromatic Theory – Hermann Von Helmholtz
Retina has receptors with chemicals (opsins) which
respond to ONLY 3 light waves
Those 3 lightwaves
(ONLY) give us millions
of hues
Feature detectors – Hubel and Wiesel
Parallel processing
Opponent Process Theory – Ewald Hering
trichromatic signals from the cones feed into neural cells
(bipolar, ganglion, etc.) which fire in an opponent fashion –
red/green blue/yellow or white/black
*In an on-off way, not at the same time
This explains the afterimage -
When staring at ½ of
color pair, it tires, and
its opposite fires
when you look away.
Humans are trichromatic – see all three color
pairs
8% of males are colorblind - dichromatic
Monochromatic – see in black, whit e
and greys
2.
Hearing (Audition)
Sound travels in waves like light
Pitch is measured in Hertz (frequency)
- Normal human hearing
range: 500 to 3,000 Hz
(16-20,000 is possible)
Intensity (loudness) is
measured in Decibels
(amplitude)
-Noises above 130 can be painful
-85 db on a daily basis can do
damage
TINNITUS – ringing in the ears: a
warning sign of hearing damage
Hearing loss usually begins in the high
ranges
STRUCTURE OF THE EAR:
INCOMING SOUND WAVE
Outer ear:
•Pinna
•Auditory
Canal
Tympanic Membrane – vibrates
at freq. of sound wave
Middle Ear:
•Hammer (malleus)
•Anvil (incus)
•Stirrup(stapes)
Oval window – ditto TM
Inner ear
•Cochlea
•Basilar membrane contains
hair cells
Hair cells: 20,000 per ear are attached to basilar
membrane, wave back & forth in fluid.
That movement causes a an
electrical impulse to fire in
connected nerve cells
Hair cells do not regenerate!!! Damage
them and they’re gone forever!!
Types of hearing loss:
-Conductive deafness
-Nerve (sensorineural) hearing loss
Theories of pitch:
3. Cutaneous Sense (Touch) – also known as a
somatosense
Only 3 types of receptors give us all of the
sensations we experience:
**More sensitive areas of
1. Pressure
body have more
2. Temperature
receptors
3. Pain
Pain is least adaptive and necessary for survival!
Babies and other animals deprived of touch are stunted
physically, mentally and have high mortality rates
Pain fibers are smaller than temp. and
pressure fibers. – body has both “slow” pain
and “fast” pain cells
**Gate Control Theory – The spinal cord acts as a gate
which can block the small slow pain fibers & release
endorphins when pressure and/or temp. fibers are
stimulated
Olfaction (smell)
Receptors are Olfactory bulbs – located high in nasal
cavity in Olfatory Epithelium
Odor molecules lock into
receptors sites on bulbs
like key into lock – only
scents with receptors can
be registered
Smell is a chemical sense and a companion to taste
*The most primitive sense – olfactory nerve is
not routed through the thalamus
*The olfactory nerve is routed alongside the
hippocampus, so smell is very evocative
5. Gustation (taste)
Bumpy, porous surface of tongue - Papillae
Under that layer lie the
receptors – Taste Buds
•Food must be in solution form to seep down to taste buds
Receptors encircle the tongue, do not exist in the
center of the tongue
The types of receptors:
Sweet, salty, sour, bitter and umami (savory)
Taste buds do regenerate!!
They regenerate more slowly with
age
ALL OF THE SENSES WORK IN COMBINATION IN A
PROCESS CALLED SENSORY INTERACTION
2 important companion senses:
*Kinesthetic sense position of body and limbs
*Vestibular sense – system of
semi-circular canals located in
inner ear
-gives us our sense of
equilibrium. Fluid in
canals moves with our
movement
These 2 + cutaneous sense give
make up the somatosenses
PERCEPTION
Perceptual organization – studied by
Gestalt psych. since mid-1800s
Grouping Principles:
*Proximity, similarity, continuity, closure and
connectedness all contribute to patterns we perceive
http://graphicdesign.spokanefalls.edu/tutorials/proce
ss/gestaltprinciples/gestaltprinc.htm
Other Gestalt Principles: reversible
figure and figure-ground
DEPTH PERCEPTION
- Recognizing distance and 3 dimensional depth in
space around us
A Nature or Nurture Issue!!
Visual Cliff – test for depth
perception in infants
- Created by Eleanor Walk and Richard
Gibson
Depth cues:
1. BINOCULAR CUES – require both eyes
*Retinal disparity – the 2 ½ inch
difference between the eyes
creates 2 disparate images
Brain
overlaps/merges
them - stereopsis
*convergence – muscular cue: amount of tension
created when eyes bring images together
•More strain – object is closer
2. MONOCULAR CUES – only require 1 eye
•Interposition (overlap)
•Relative size
•Linear perspective
•Aerial perspective (relative clarity)
•Texture gradient
•Relative height
•Relative motion
•Light & shadow
Relative Height
Linear perspective
Relative size
Perceptual Constancies
Size constancy, shape constancy, color and
brightness constancies all keep our world
unchanging
Perceptual Set:
-a predisposition to view the world from a particular
perspective (a product of our schema)
Context Effects: perception is influenced by the
situation/environment (also a product of schema)
READ Perceptual Adaptation
ESP – 4 types:
1.
2.
3.
4.
Telepathy
Clairvoyance
Precognition
Psychokinesis (telekinesis)
**PSYCHOLOGY
DOES NOT
SUPPORT ESP AS
SCIENTIFIC
PHENOMENON!!
Apparent motion:
Autokinetic effect, phi
phenomena and stroboscopic
motion