sensation and perception modules 5 & 6. what’s the difference?? sensation: the process by...
TRANSCRIPT
Sensation and PerceptionModules 5 & 6
What’s the difference?? Sensation: the process by which sensory
systems and the nervous system receive stimuli from our environment
Bottom-up processing: info processing that analyzes raw stimuli entering through the many sensory systems
Perception: process of organizing and interpreting incoming sensory info
Top-down processing: info processing that draws on expectations and experiences to interpret incoming info
• Weakest amount of a stimulus that can be sensed
• Has been found for vision, hearing, smell, touch
• Varies depending on psychological and biological factors
ABSOLUTE THRESHOLD
•AKA " just noticeable difference"•Minimum amount of difference that
can be detected between 2 stimuli(paint colors)
- How much do the laces on your shoes need to be loosen so that they feel less
tight?- How much does the volume have to increase before you can tell that your
stereo has gotten louder?
DIFFERENCE THRESHOLD
Are subliminal messages a real thing??Subliminal = “below threshold”
• Investigates the effects of the distractions and interferences we experience while perceiving the
world• Developed during the Cold War
• Attempts to explain & predict the different perceptual mistakes we
make• Variables to consider:• Stimulus variables
• Environmental variables • Organism variables
SIGNAL-DETECTION THEORY
• Process by which we become more sensitive to weak stimuli and less sensitive to unchanging stimuli
• Ex: living in the city, odors, darkness at the movie theater, temperature
SENSORY ADAPTATION
Selective Attention
REVIEW
1.Define absolute threshold.2.Give 2 examples of sensory
adaptation.3.What is the difference between sensation and
perception?4.What is difference
threshold also known as?5.What is the signal
detection theory?
• Light is electromagnetic energy• Described in wavelengths
• Light visible to humans only makes up a small part of the spectrum• Wavelength = color
• Amplitude = brightness• Human photoreceptors in the eye are sensitive to wavelengths of light energy
called the visible spectrum. (photoreceptors --> brain)
• ROY G BIV
VISION
• Light enters the eye and then is projected onto a surface
• Cornea --> part of the sclera; bulge on front of eye: focuses light by bending
toward a central focal point; protects eye• Amount of light that enters is determined
by size of opening (pupil) in the • colored part of our eye --> iris• Opening --> pupil: size adjusts
automatically based on the amount of light entering eye; sensitive to emotions
THE EYE
• Once light enters the eye, it encounters the lens
• Lens adjusts to the distance of objects by changing its thickness
• As the light passes through the lens, images are flipped and inverted
• These changes project a clear image of the object onto the retina
(focuses image)
Cont…
So essentially….
Light travels through the pupil to the lens and is then reflected onto the retina. The optic nerve sends the visual information to
the brain.
Rods - located in retina's periphery; sensitive only to brightness of light; allow us to see in
black & whiteCones - located in the middle of retina; involved
in color perceptionBlind spot - where the optic nerve connects to
the eye and contains neither rods or conesActivity 2.2
RETINA CONTAINS THESE RECEPTOR CELLS...
DEMONSTRATION
1. For the first demonstration, hold the side of the paper with the X and Y at arm's
length while covering one eye with the other hand. If the left eye is covered, fixate on the X (assuming it is on the
left), and vice versa. Then slowly advance the paper toward the eye. Notice what happens to the Y: At some critical distance from the eye it disappears, but as the distance
from the eye is further decreased, it reappears. You should then be able to tune the Y in and out by adjusting the
distance of the paper from the eye.
2. The second demonstration involves using the side of the paper with the X, Y, and Z; holding it at arm's length; fixating on the Y with the left eye covered; and slowly advancing the paper toward the eye. At some critical
distance from the eye, the Z will disappear. If the paper is then held at this point, it is possible to observe an unusual
phenomenon: Shifting fixation to the X causes the Y to disappear and the Z to reappear. Thus, by shifting fixation back and forth between and Y and the X, you can make the
Z and the Y alternately pop in and out of view.
Young - Helmholtz trichromatic theory - retinas contain 3 types of cone cells, each responding best
to a particular wavelength: blue, green, redOpponent process theory - two-color processes,
red vs. green, yellow vs. blue, black vs. white (complementary colors)
OPT explains afterimage p. 84Color blindness - absence/ malfunction of cones
(monochromatic and dichromatic)The Stroop Effect/interference
COLOR VISION
Figure 4.19Demonstration of a complementary afterimage. Stare at the dot in the center of the flower for at least 60 seconds, then quickly shift your gaze to the dot in the white rectangle. You should see an afterimage of the flower—but in complementary colors.
REVIEW!!!
1. What are rods and cones?2. Where is the blindspot located?3. Provide one example of difference
threshold.4. What is the stimulus for light?5. You’re holding your dog’s leash as
he calmly lays down. Your friend comes up to talk to you…after several minutes you accidently drop the leash. What is this an example of???
VISION
HEARING
Sound is mechanical energy typically caused by vibrating objectsVibrations produce movement of air
molecules (sound waves)Moving one's head helps in
detecting the source of a soundLocating sound is automatic; in
front and behind is more difficult (uses other senses)
HEARING
Frequency - corresponds to pitch; measured in hertz (Hz) [vocal chords - more cycles = higher
pitch]; 20-20,000 HzAmplitude - corresponds to loudness; measured in decibels (dB); 0 dB threshold = ticking of a
watch 20 ft away in quiet room
CHARACTERISTICS OF SOUND
Outer/middle/innerPinna - visible skin/cartilage
Auditory canal --> eardrum (tympanic membrane)
Eardrum - gateway to the middle ear; thin membrane that vibrates when sound waves
strike it (damage)Ossicles - located in the back of the
eardrum; 3 small bones that pick up and transmit vibration
1. Hammer2. Anvil
3. Stirrup (smallest bone in the body)
THE EAR
Cochlea - inner ear; fluid-filled, snail-shaped bony tube
Vibrating fluid stimulates hair cells --> tiny projections in cochlea that are receptor
cells for hearingEnergy is converted to neural impulses that
are transmitted to the brain via auditory nerve --> projected to hearing areas of
cerebral cortex (temporal lobe)
Cont…
2 million people are deafConductive deafness - sound waves are
unable to be transferred from the outer ear to inner ear; damage to the ossicles (middle
ear) – unable to vibrate (hearing aids)Sensorineural deafness - damage to the
inner ear or hair cells in the cochlea (disease or trauma); people are unable to
hear certain frequenciesActivity 2.3
DEAFNESS
REVIEW1. What determines loudness? How is it measured?
2. How do we SEE? Describe the process, listing the parts involved.
3. How do we HEAR? Describe the process, listing the parts involved?
4. How do we see in color?
5. What is an afterimage? What theory describes this phenomenon?
6. What is the smallest bone in the body?
7. What takes information from the eye to the brain?
8. Where does auditory information go to in the brain? (What lobe???)
9. What is the stimulus for vision? For hearing?
10.Describe 2 types of deafness.
Starbursts!Molecules are given off by substances
Olfactory cells carry it to the olfactory bulb, which activates the prefrontal cortex amygdala/hippocampus
Olfactory nerve sends info to brainOdors can evoke highly emotional memories
Women detect odors more readily than men; brain responses to odors are stronger in women
Pheromones - same-species odors, form of chemical communication
Anosmia - loss of sense of smell
SMELL
Also known as gustationReceptor cells are located in the taste buds
Receptors are sensitive to 4 basic taste qualities:1. Salty2. Sweet3. Sour4. Bitter
5. UmamiReceptor cells reproduce rapidly enough to completely
renew in a week1/4 of population are "supertasters"
TASTE
Skin senses pressure, temperature, and painTouch is vitally important to infants and elderly
Pressure --> hairTemperature --> relative
Pain --> prostaglandins are chemicals that help body transmit pain messages to the brain (aspirin
curbs production); endorphins block release
TOUCH
Message sent to spinal cord to thalamus then projected to cerebral cortex which registers the
location and severityGate-control theory - only certain amount of info
can be processed by nervous system at a timePain messages travel on one set of nerve fibers in
spinal cord, and all other sensory messages travel along another set
Fibers carrying pain messages have pain gates that open
Non-pain fibers can close gates if there is a competing stimulation to larger nerve fibers
(rubbing/icing)
PAIN
Vestibular sense - located in your inner earProvides information about your overall
orientationRelies on fluid-filled semicircular canals in ear
Concerned with balance and body position Kinesthesis - communicates information about movement and location of body parts; relies on
receptors in muscles and joints (touch nose/"falling asleep")
Activity 3.1 – Sensory Interdependencies
BODY SENSES
“Maybe each human being lives in a unique world, a private world different from those
inhabited and experienced by all other humans. . If reality differs from person to
person, can we speak of reality singular, or shouldn't we really be talking about plural
realities? And if there are plural realities, are some more true (more real) than others? What about the world of a schizophrenic? Maybe it's as real as our world. Maybe we cannot say that we are in touch with reality and he is not, but should instead say, His reality is so different
from ours that he can't explain his to us, and we can't explain ours to him. The problem, then, is
that if subjective worlds are experienced too differently, there occurs a breakdown in
communication ... and there is the real illness.” ― Philip K. Dick
Gestalt (remember this???) - the whole experience is greater than the sum of the
individual parts; we don’t focus on individual stimuli in our environment – we group them into
more meaningful unitsClosure - tendency to perceive a whole figure
even if there are gapshttp://www.youtube.com/watch?v=nxKcpfFvuf8
PERCEPTION
Closure
A Gestalt
Figure-ground perception - perception of figures against a background
Grouping Principles: proximity, similarity, continuity, common fate
Perception of movement - relative; waiting at a light
Stroboscopic motion - drawing books, movies; law of continuity - prefer to see things as one
continuous image
PERCEPTION
Figure-ground Perception
Figure-Ground
Grouping Principles
Monocular cues - depth cues provided by one eye
Motion parallax
Texture gradient
Shadow
Overlapping/interposition
Clearness
Linear Perspective
Binocular cues - depth cues provided by both eyes
Retinal disparity
Convergence
DEPTH PERCEPTION - PERCEIVED BY USING A NUMBER OF CUES
Monocular cues Motion Parallax Texture Gradient
Monocular Cues Shadow Overlapping Interposition
Monocular Cues Linear Perspective
Binocular Depth Cues: Finger Sausage
Perceptual illusions occur when sensory stimuli are misinterpreted; reveal the strategies we use
to interpret sensations correctlyMuller-Lyer
PonzoThe Ames room
VISUAL ILLUSIONS
Muller-Lyer
Ponzo
Size Distance Relationship
Size Distance Relationship
Size Distance Relationship
SizeShape
Lightness
PERCEPTUAL CONSTANCY
Perceptual Constancies