Notes Chapter 6 Part I
Thresholds and Attention/Intro Sensation
I.
What is sensation?
SENSATION: Receiving messages about the world!
LEFT
THE BRAIN SITS INSIDE THE SKULL, PROTECTED AND ISOLATED FROM EXTERNAL EVENTS THAT SURROUND US. IT
IS ALMOST CONSTANTLY BEING BOMBARDED BY THE "CLICKING" OF CODED NEURAL MESSAGES COMING IN OVER
MILLIONS OF NERVE FIBERS. THE MESSAGES ON THE OPTIC NERVE ARE NOT ANY MORE VISUAL THAN THE "CLICKS"
ON THE AUDITORY NERVE, BUT THEY RELIABLY PRODUCE VISION AND SOUND. EACH INPUT HAS SPECIFIC NERVE
ENERGIES!
RIGHT
RIGHT
THE WORLD IS KNOWN TO US ONLY INDIRECTLY BECAUSE OUR BRAINS ARE NOT IN DIRECT CONTACT WITH THE
OUTSIDE WORLD. BUT SENSORY RECEPTOR CELLS HAVE THE ABILITY TO TRANSLATE PHYSICAL ENERGY INTO CODED
NEURAL MESSAGES THAT ARE SENT TO THE BRAIN (SENSATION) WHERE THEY ARE INTERPRETED (PERCEPTION). NOT
ALL FORMS OF PHYSICAL ENERGY CAN BECOME PART OF OUR PERCEPTION OF THE WORLD: (1) WE MUST HAVE
SENSORY RECEPTOR CELLS THAT CAN TRANSLATE THAT FORM OF ENERGY. (2) THE STIMULUS MUST BE STRONG
ENOUGH TO EXCEED THE SENSORY THRESHOLD. (3) THE STIMULUS MUST BE ATTENDED TO BECAUSE OF ITS
IMPORTANCE, INTENSITY, OR FOR SOME OTHER REASON. OUR PERCEPTION OF EXTERNAL REALITY IS COMPLICATED
BY THE FACT THAT THERE IS NOT A SIMPLE AND DIRECT RELATIONSHIP BETWEEN THE PROPERTIES OF PHYSICAL
STIMULI AND OUR CONSCIOUS SENSATIONS. FOR EXAMPLE, A SMALL CHANGE IN THE LOUDNESS OF A STEREO IS
NOTICEABLE WHEN THE STEREO IS BEING PLAYED SOFTLY, BUT THE SAME CHANGE WOULD GO UNNOTICED IF THE
STEREO WAS AT A HIGH VOLUME. THE COMPLICATED RELATIONSHIP BETWEEN PHYSICAL STIMULI AND CONSCIOUS
SENSATION IS THE SUBJECT OF PSYCHOPHYSICS.
LEFT
II.
THE SIX SENSES
Psychophysics
A.
BOTTOM
STIMULUS (Physics)
Physical Change –
Anything that EXCITES
sensory neurons
(internal/external)
Light
Sound
Balance
Pressure
Chemical
SENSATION
Awareness of sound,
taste, touch, smell, sight, etc.
TOP
PERCEPTION(Psycho)
Organization of
sensation into a
meaningful whole
Sense
Stimulus
Sense Organ
Receptor
Sensation
Sight
light waves
eye
rods and cones
color, patterns, texture
Hearing
sound waves
ear
hair cells of
basilar membrane
noises, volume, pitch,
tone
Touch
external contact
skin
nerve endings in skin
touch, pain, warmth,
Cold
Smell
chemicals
nose
hair cells of olfactory
epithelium
odors
Taste
soluble substances
chemicals
tongue
taste buds
sweet, sour, salty, bitter,
umami
Equilibrium
mechanical and
gravitational forces
inner ear
cerebellum
hair cells of semicircular canals and
vestibular sacs
movement, body position
gravitational pull
A.
When learning about the senses we focus on:
1.
Bottom-up Processing
Starts with the receptors (bottom), ends
with the brain (top). Psychophysics
Outside to the inside.
B.
vs.
2.
Top-down Processing
Starts with thinking/brain(top)
ends with actual sensation/receptors (bottom).
Inside to the outside.
Thresholds
1.
Absolute Threshold (ABSOLUTE lowest threshold for sensory awareness)
a.
smallest amount of energy that will produce a sensation about 50% of the time.
*wings of a bee on cheek
*light of candle on clear dark night from 30 miles away
b.
usually VERY low – we are sensitive to sensations
c.
not TOO low – RAS filters for focus
*sensory adaptation – tuned to change
2.
Difference Threshold (JND) (Threshold for noticing a CHANGE – already sensing, now it will change)
a.
just noticeable difference – the smallest amount of change in a stimulus that will produce a
change in sensation.
b.
Weber’s Law (physics)
3.
Superliminal – above the threshold for conscious awareness
4.
Subliminal – below the threshold for conscious awareness
a.
Freud
influences our unconscious mind, which influences our behaviors and mental processes
b.
Brain Research – priming/cues
activate neural networks, make us more likely to think about something
act as a memory cue
c.
Examples
http://www.youtube.com/watch?v=1QYYOuQGEp0
Subliminal Messages, Puzzles, Illusions, Brain Teasers.mht
Notes Vision
I.
What is the path light takes as it is transduced? – the psychophysical process of vision
A.
Light enters the eye through the cornea.
B.
The iris expands and contracts the pupil through which the light moves. (test)
C.
The lens bends or accommodates (like a schema) to focus the light on the where the rods and cones, or are located.
D.
The rods and cones send signals of black and white (rods) as well as color (cones).
E.
The central focus of color vision is the fovea, which is made up mainly of cones.
1.
The RETINA: (How and what do the eyes SEE!)
a.
Rods/Cones leave the eye and pass through the bipolar cells as well as ganglion.
cells.
b.
The axons of the ganglion cells converge to form a nerve known as the optic nerve.
c.
d.
F.
Where the optic nerve leaves the eye there are NO rods and cones. This is known as your blind spot.
*Page 239
*Cover LEFT EYE/focus on dot(line up with right eye)
*Partner HOLDS BOOK 12 in. away
*Move slightly forward or back until car disappears from visual field
Cones are more concentrated on the fovea (center of the retina).
Finally, the signal leaves the eye through the optic nerve and is sent to the top of the processing route, or the occipital lobe.
II
How do we see?
A.
In vision and hearing, what we see and what we hear are determined by waves.
B.
Light waves and sound waves have both:
1.
Wavelength:
2.
Determines hue (color)
Shorter = cool colors (purple 400 nanometers)
Longer = warm colors (red = 650 nanometers)
Amplitude:
Determines intensity of color/richness
C.
D.
Define Acuity:
The clarity with which you see. Greater acuity, better your vision.
1.
What makes you nearsighted? Sighted for NEAR things. Eyeball long – objects focus in front of retina
2.
What makes you farsighted?
Sighted for FAR things.
Eyeball short – objects focus in back of retina
Feature Detectors
1.
HUBEL and WEISEL discovered feature detectors that respond to the features of a stimulus entering the
eye.
a.
Examples of FEATURES: Shape/Angle/Movement
http://www.learner.org/resources/series142.html?pop=yes&pid=1576 \
Motion Detector Video Clip (WOWZA!!) www.illusionworks.com
http://www.youtube.com/watch?v=0JVJsPpg1-8
E.
Perception of visual information.
1.
Look at the face of the person next to you.
2.
What do you “see”? What do you “think” as you look at him/her?
3.
What part(s) of your brain are affected by this vision?
Hippocampus (memory)
Temporal lobes (long-term memory/facial recognition)
Occipital lobes (visual processing)
Thalamus and Reticular Formation (RAS) – filter and send signals to correct lobes
Limbic System/Frontal Lobes – emotional reactions/personal reactions
*Visual Capture – tendency for vision to override all other sensations
http://www.cbsnews.com/video/watch/?id=1817451n&tag=related;photovideo
Which senses are heightened as a result of his blindness?
4.
Parallel Processing: - All of the above happened at once. Simultaneous detection.
5.
Blindsight: Example – Respond to something in visual field but can’t “perceive”. No parallel processing.
Blindsight.wmv
F.
Color Vision
1.
Color-blind people lack functioning cones.
a.
Monochromat
b.
black/white/gray
Dichromat
red/green or yellow/blue
c.
Trichromat
see all colors in visual spectrum
2.
Statistics:
1 in 10 men are color blind. This is a sex-linked trait.
The x chromosome carries – with women if one x carries color-blindness gene, other can counteract
For men, if x chromosome carries – the y can’t counteract
3.
Opponent Process Theory of Color Vision versus the
Explains dicromatism
Visual info leaves receptor cells, we analyze opposing color
Neurons turned “on” and “off”
Second stage of visual processing – on way to cortex
4.
Trichromatic Theory of Color Vision:
First stage of visual color processing
cones work in teams of three – red, green, blue
Combos of these colors make up all color vision