Lecture 7 Flashcards
Sensation
stimulus detection process where our sense organs respond to and translate stimuli into nerve impulses sent to the brain.
Perception
active process of organizing stimulus input and giving it meaning
Stimulus Detection
How intense does a stimulus need to be for us to recognize its presence?
Absolute Threshold
vision candle flame @ 30 miles on a clear night
hearing watch (clock) ticking @ 20 feet a quiet room
taste 1 tsp sugar in 2 gallons of H20
smell 1 drop of perfume in 6(3) room apt (Square foot?)
touch wing of fly on cheek dropped from 1 cm
Just Noticeable difference
The minimum change in a stimulus that can be detected
weber’s law
the difference threshold is directly proportional to the magnitude of the stimulus to which the comparison is being made.
e.g. Value for weight is 2-3%
If you want to know if you pick up the change in the strength of the stimulus, is that you have to know the strength of the original stimuli. It is proportional to what the original weight
Backpack example: put calculator in, already really heavy, won’t notice. If really light, and something added, will feel the difference
Fechner’s law
larger and larger increases in physical energy are required to produce equal increases in perception
e.g. Light bulb example: dark to light: really light, from 0 to 25à that’s light.
But 25-50à don’t think it is as light. Need bigger proportion
Signal Detection Theory
various factors influence our sensory judgment; often involves a process of decisions in addition to sensation
→ home alone, watching a scary movie→ heightened to the sounds
Sensory Adaptation
over time neurons decrease activity in response to a constant stimulus
→ commercials→ higher volume
Vision
The normal stimulus for vision is electromagnetic energy or light waves
Light waves are measured in nanometers
Our visual system is sensitive to wavelengths extending from ~700 nanometers (red) to ~ 400 nanometers (blue-violet)
Where do light waves enter the eye?
the cornea
The pupil
behind the cornea, the pupil adjusts to control the amount of light that enters the eye
The iris
The pupil’s size is controlled by muscles in the colored iris that surrounds the pupil
The Lens
behind the pupil
focuses images onto the retina, reversing the image from right to left and from top to bottom; the brain reconstructs it into the image we perceive
Retina
contains specialized sensory neurons
contains the rods and the cones
The Optic Disk
is a hole in the retina; it yields a blind spot which we don’t experience as a “hole” as each eye compensates for the blind spot on the other.
Rods
function best in dim light, primarily black/white brightness receptors, more sensitive to light than cones, no color sensation
Cones
function best in bright light, serve as a color receptors
-color blind: still have cones, might misfire or act in a different wayRods and Cones translate light waves into..
Nerve impulses which pass through the retina
Optic Chiasm
where the optic nerves from each eye cross over and pass information to the opposite side of the brain
Hue
commonly what is meant by color
Saturation
the color’s purity, how diluted is it with black or white
Trichromatic Theory
three types of color receptors in the retina; individual cones are most sensitive to either red, blue or green. Couldn’t explain afterimages
Color-Opponent System
each type of cone responds to two different wavelengths; red/green; blue/yellow; black/white
1st color vision theory
The eye has three types of cones with each being sensitive to a different band of wavelengths (supports trichromatic)
2nd color vision theory
Cells have been found which respond in opposite ways to red vs green and blue vs yellow (supports color-opponent process)
Infant Vision
Infants are born with a functional/intact visual system; visual accommodation is not well developed. They focus on high contrast images and show a preference for human faces
Audition
stimuli for hearing are sound waves
Frequency
the number of sound waves, cycles per second. Most common sounds are in lower frequencies
Pitch
the quality of a tone from low to high, the number of times particles oscillate per second
Amplitude
the height/depth of a wave; corresponds with loudness; the greater the amplitude the louder the sound
Complexity/Timbre
the wave purity or mixture of sound
the ear
Sound waves travel into an auditory canal leading to the ear drum; a moveable membrane which vibrates in response to sound waves This leads to the middle ear. When the eardrum vibrates it sets in motion the hammer, anvil and stirrups which amplify the sound waves
The Cochlea
a fluid-filled tunnel has tiny hairs or cilia’s which are the sound receptors. They move in different directions, triggering the sensory neurons and an action potential
Temporal Code/Frequency Theory
nerve impulses sent to the brain match the frequency of the sound waves
Place Code/ Place Theory
different areas of the basilar membrane are sensitive to different frequencies
Development of Hearing
Research indicates the fetus can hear 3 months prior to birth
Newborns have been shown to recognize books and voices and respond differentially to familiar voices and music
Changes in sensitivity to frequencies occurs as one ages. Older individuals are less sensitive to sounds at higher frequencies (mosquito ringtone)
Olfactory Receptors
humans have 10 million
The Upper Portion of the nasal passage
detects smells which travel straight to the base of the brain at the olfactory bulb
Pheromones
chemical signals which are found in natural body scents in humans and other species
Four Qualities of Taste
sweet, sour, salty and bitter
Taste buds
Humans have about between 5,000-10,000 taste buds
Taste buds can regenerate—but lose over time
Three Primary Sensations
pressure, temp, and pain
Kinesthetics
the body’s way of giving feedback about our muscle and joint position; gives us a sense of coordinated movement
Vestibular System
in the inner ear; helps with balance and maintaining our equilibrium in space
Visual allusions
Most visual illusions occur because of perceptual constancies which usually help us perceive more accurately
Perceptual Schemas/Template
mental representations or images for comparisons
Form Perception
organization of sensations into meaningful shapes and patterns
Gestalt Principles
perceptual constancy, size constancy
Perceptual Constancy
objects appear to be relatively stable despite changes in the stimulation of sensory receptors
Size Constancy
objects do not appear to change in size when viewed from different distances
Inattentional Blindness
failure to perceive objects that are not the focus of our attention
Change Blindness
failure to perceive/detect changes in the details of a scene
Retinal Disparity
objects project images to different locations on the right and left retina, which give a different view of the object. The closer an item gets the greater the disparity between the images on the eye
Depth Perception
retina receives information in 2 dimensions, length and width and the brain translates into 3 dimensions. Uses binocular and monocular cues.
