PSYCHOLOGY CLASS # 6
SENSATION AND PERCEPTION
PART II
SENSORY ADAPTATION - our diminishing sensitivity to an unchanging stimulus.
To experience this…..move your watch up your wrist….you will feel it but only for a few moments…..After constant exposure to a stimulus, our nerve cells fire less frequently.
So, why is it that when we stare at an object…it doesn’t vanish from sight?
Because our eyes are always moving…… flitting from spot to spot..enough to guarantee that stimulation on the eyes’ receptors continually change…
What kinds of sensory adaptations have you experienced in the last 24 hrs.
Eyes adapting to changes in light
Body adapting to changes in air temperature or water temperature
THE VISUAL SYSTEM
psychology the visual system - search THE EYE AND VISION…………………….4:24
Review diagram of the eye p. 172
1. Retina………….126 million receptor cells
2. Rods - work @ night - sensitive to light but not useful in color vision
3. Cones - the receptors that we use for color perception
4. Fovea - only cones and where vision is best5. Blind spot - p. 174 - where the optic nerve is - contains no rods or cones
VISUAL PROCESSING IN THE BRAIN
The eyes are just the beginning of visual perception. The next step is when nerve impulses from the retina, travel through the optic nerve to the brain where they (the sensations) are analyzed and interpreted into vision (perception).
First stop is the Thalamus - the relay station and then on to the visual cortex…..p. 175 fig 5.15
The Visual Cortex - is located in the occipital lobe …visual information is processed further here and then transmitted to other visual areas of the brain
Within the visual areas of the brain are special neurons known as Feature Detectors.These neurons are sensitive to different types of lines and angles which help in identifying the ‘features’ of an object.
Parallel processing - the simultaneous distribution of information across different neural pathways.
This helps information to travel rapidly through the brain.
With visual perception there is parallel processing in the ‘what’ and ‘where’ pathways.
The ‘what’ pathway is in the temporal lobe and processes information about what the object is
Damage in this area can result losing the ability to recognize faces
The ‘where’ pathway is in the parietal lobe and processes information on an object’s location including movement and depth
Damage in this area can result in losing the ability to differentiate between parked and moving cars.
BINDING - the bringing together and integration of what is processed by different pathways into a unified perception for ex. Dog…..enters the visual system through the eyes as a complete object…..then the sensory system breaks down the information and transmits it along different pathways and then must ‘bind” all of the information back together into the perception of a complete object again.
Exactly how binding occurs is not known but is being heavily researched.
COLOR VISION
In the 1800’s physiologists proposed two theories related to color vision which have been confirmed by later research:
1. The Young - Helmholtz trichromatic theory - (3 color)
All color is produced by only 3 types of cone receptors - green, red, & blue
2. Opponent - process theory - developed by Hering
He observed that some colors go together or can blend, whereas others cannot.
For ex. Greenish-blue or yellow-orange these can blend together
Reddish - green or bluish - yellow……these don’t blend
This theory states that receptor cells are excited or inhibited in pairs of colors
Either red-green or blue-yellow
Hering studied afterimages see p, 177
Research has indicated that the eye and the brain use both the trichromatic theory and the opponent - process theory to code colors
Color blindness - in the most common form, the green cones malfunction
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DEPTH PERCEPTION - the ability to perceive objects three - dimensionally
To see depth you use two types of cues : binocular and monocular
Binocular cues: the disparity (difference) in the images in each eye is the binocular cue that the brain uses to determine depth…in other words…distance from an object - see p. 180
Monocular cues: we also use these cues, based on the image in one eye, to determine depth perception
1. Familiar size……we are familiar with what the relative size of an object should be
2. Height in the field of view: higher objects are usually farther away
3. Linear perspective…objects further away are smaller
4. Overlap - an object that overlaps another, is seen as closer
5. Shading - changes in perception based on shading and lighting
6. Texture gradient - texture becomes smaller and denser the farther away it is
Artists use these cues all the time as they attempt to paint a 3-dimensional world on a 2 dimensional canvas. Because monocular cues are used so frequently by painters, they have become known as pictorial cues.
MOTION PERCEPTION
We’ve talked about how this plays an important role in the survival of many species.
How do we perceive motion? -
1. We have neurons that are specialized to detect motion.
2. We get feedback from our body as to whether we are moving or something else is moving
3. The environment gives us cues that give us information about movement.
Psychologists are interested in studying real movement and the phenomenon ofapparent movement - which occurs when an object is stationary, but we perceive itas moving.
Ex. IMAX movies………….drive thru carwash
Types of apparent movement -
1. stroboscopic movement - movies
2. Movement aftereffects - when we watch motion, and then look to another surfaceAnd see motion in the opposite direction…..figure 5.27 p. 183.
PERCEPTUAL CONSTANCY - the recognition that objects are constant and unchanging even though sensory input about them is changing.
1. Size constancy - recognition that an object’s size remains the same even though theretinal image of the object changes p.183 figure 5.282.
Shape constancy - recognition that an object’s shape remains the same even if it’s orientation to us changes p. 184 figure 5.293.
Brightness constancy - recognition that an objest retains the same degree ofbrightness even though different amounts of light fall on it
ILLUSIONS
A visual illusion occurs when there is a discrepancy between reality and the perceptual representation of it.
Illusions can provide insight into how perception works.
Review different illusions and try to identify which perceptual cue is involved?
Familiar size
Height in the field of view
Linear perspective
Overlap
Shading
Texture gradient
Apparent movement - stroboscopic or aftereffects
Size, shape, or brightness constancyafterimages
THE AUDITORY SYSTEM
Auditory system - audition -
HEARING
How do we do it?
Sound travels in waves of compressed air…sound shoves the air molecules
When these sound waves hit the ear, these sensations are transmitted to the brain
Anatomy of the ear- outer ear, middle ear, and inner ear
1. The outer ear funnels sound waves to the eardrum.
2. The bones of the middle ear amplify and relay the vibrationsfrom the eardrum through the oval window into the fluid-filled cochlea.
3. The pressure changes in the fluid in the cochlea, cause the Basilar membrane to ripple, bending the hair cells on the surface.
4. Hair cell movements trigger impulses that travel along nerve fibersTo the auditory nerve.
5. The auditory nerve carries these messages to the Thalamus.
6. From the thalamus, the neural messages go on to the auditory cortex in the temporal lobe.
How do we detect loudness?
The louder the sound, the more hair cells are activated.
How do we discriminate pitch? The high pitch of a bird vs. the low pitch of a truck?
Two theories - place theory and frequency theory
PLACE theory - different pitches trigger activity at different places along the basilarmembrane in the cochlea. So the brain interprets pitch from the place where the nerves are activated.
But this didn’t explain low pitch sufficiently, since low pitch sounds are not as specifically located on the basilar membrane as initially thought.
FREQUENCY theory - explains pitch in terms of the frequency of nerve impulses traveling up the auditory nerve…different pitches cause nerves to fire at different freq.
But certain pitches would require nerves to fire faster than 1000 times per second which they can’t do. So the volley principle - - explains how this is possible…nerve cells can alternate firing….some fire while others rest and reload…..together they can achieve a combined frequency of 1000 times per second.
How do we locate sounds?
Sound waves strike one ear sooner and more intensely than the other. From this, the brain can compute the sound’s location.
The intensity of the sound to the opposite ear is reduced by what is called the sound shadow, which is created by the head .
But more difficult to locate a sound when it’s directly in front because sound waves hitting each ear equally and no sound shadow. Ex. In classroom.
THE SENSE OF SMELL -
Smell is called Olfaction….the olfactory system
Smell is a chemical sense
1. Airborne odor molecules travel up the nasal passages to the olfactory receptor cells
2. These olfactory receptor cells send messages to the brain’s olfactory bulb …not to theThalamus
3. From the olfactory bulb, messages are sent to the temporal lobe’s primary smell cortex and to parts of the limbic system a more primitive part of the brain involved in memory and emotion.
Because olfactory messages are sent to the limbic system which is involved in memory and emotion….it explains why certain smells can trigger emotions and memories…smell memories.
Examples of smell memories??
CHAPTER 6
STATES OF CONCIOUSNESS
CONSCIOUSNESS - There are two aspects of consciousness - awareness and arousal
Consciousness is defined as the awareness of external events and internal sensations, including awareness of the self and thoughts about one’s experiences. This awareness occurs under a condition of arousal which is the physiological state of being engaged with the environment
.Information moves rapidly in and out of our consciousness.
William James…..the functionalist….first coined the term….stream of consciousness to describe what occurs in the mind - and described it as a continuous flow of changing sensations, images, thoughts, and feelings.
P. 209 chart to describe the 5 levels of awareness
Higher level consciousness involves controlled processes - in which individuals actively focus their efforts toward a goal.
They require selective attention that wetalked about in Chapt. 5 on Sensation and Perception - which is the ability to focus on a specific aspect of experience while ignoring others.
Ex. move your right foot in a smooth counterclockwise circle while writing the number 3(or use left if left-handed)
For the musically inclined : tap a steady 3 times with your left hand while tapping 4 times with your right hand.
Lower - Level Consciousness - includes automatic processes and daydreaming
1. Automatic processes - are states of consciousness that require little attention and do not interfere with other ongoing activities
2. Daydreaming - “mind wandering” - thinking about other things than where you are in the moment
SOMETHING THAT INVOLVES BOTH LEVELS OF HIGHER AND LOWER CONSCIOUSNESS - TALKING ON THE CELL PHONE WHILE DRIVING ****
Talking on the phone is selective attention and driving is automatic process
Because attention is selective, attending to a phone call or GPS or DVD player causes inattention to other things.
There was a study that analyzed reports for the moments before a car crash.They found that cell phone users…even hands-free…were 4 times more at risk of an accident.
Having a passenger only increased the risk by 1.6 times….it is believed that this is less of a risk because passengers can see the driving demands and pause their conversations accordingly.
Another study instructed drivers to drive onto the highway and to exit at a rest stop 8 miles ahead.
88 percent of people driving with a passenger did as they were instructed, and exited at the rest stop.
But only 50 of the people talking on a cell phone exited as they were told to at the rest stop….they drove on by.
SLEEP
- What is the function of sleep?
It may have evolved for the following 5 reasons:
1. Sleep protects us - it kept us out of the dangers of the dark
Animals with the most need to graze and the least ability to hide, tend to sleep less Pg. 216
2. Sleep helps us recuperate - it helps to repair and restore brain tissue
3. Sleep is for making memories - for restoring and rebuilding our fading memoriesof the day’s experiences
People trained to perform tasks recall them better after a night’s sleep, or even after a short nap, then after several hours awake
4. Sleep feeds creative thinking - dreams have been known to inspire famous achievements also, sleep boosts our thinking and learning
After working on a task, then sleeping on it, people solve problems more insightfully than those who stay awake.
5. Sleep may play a role in the growth process. - during deep sleep, the pituitary gland releases a growth hormone._________________________________________________________________
____THE NEED FOR SLEEP video -
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_WHAT ARE THE MAJOR SLEEP DISORDERS?
1. Insomnia. - persistent problems in falling or staying asleep.
From middle age on, sleep is seldom uninterrupted. Being occasionally awakened is the norm.
2. Narcolepsy - periodic, overwhelming sleepiness
1 in 2000
When an individual drops off to sleep they immediately enter REM sleep
Must exercise extreme caution re driving
American Sleep disorders Association says: “Snoozing is second only to Boozing”re traffic accidents
It is treated with medication - provigil, nuvigil and melatonin
Genetic cause….. Low levels of orexin…a neurotransmitter linked to alertness
3. Sleep apnea - 1 in 20**
- apnea means “with no breath” and people with this condition intermittently stop breathing during sleep…
Usually snoring, followed by stoppage in breathing, then snorting in air…can happen hundreds of time during the night
Individuals feel sleepy and irritable during the day
It can contribute to depression, hypertension and increased risk of heart attack and stroke
Associated wih obesity… .but not in all cases.
Treatement….c-pap face mask or surgery, and in the cases of obesity, weightloss
4. Night terrors - mostly in children - not like regular nightmares - occur during Stage 4 sleep. Nightmares occur in REM sleep
They do not fully awaken…but may get up and appear terrified
End of class.
