Chapter 4/8 Sensation and Perception
Sensation: stimulation of sense organs Ex. Absorbing sound waves from band Perception: the selection, organization, and interpretation of sensory input Ex. Enjoying the music.
Psychophysics: study of how physical stimuli are translated into psychological experience Threshold: dividing point between energy levels that do and do not have detectable light Absolute threshold: for a specific type of sensory input is the minimum amount of stimulation that an organism can detect 50% of time. Imagine this 30 miles away!! Think you could still see it?????
Sense Absolute Threshold! Vision Hearing Taste Smell A candle flame seen at 30 miles on a dark clear night The tick of a watch under quiet conditions at 20 feet One teaspoon of sugar in two gallons of water One drop of perfume diffused into entire volume of a six-room apartment Touch The wing of a fly on your cheek from a distance of 1 centimeter
Just noticeable difference (JND): smallest difference in the amount of stimulation that a specific sense can detect Ex turning music down Weber s Law: size of a just noticeable difference is a constant proportion of the size of the initial stimulus Ex. Weight lifting. Fechner s Law: magnitude of sensory experience is proportional to the number of JNDs that the stimulus causing the experience is above absolute threshold Ex. One light vs. two lights is not twice as bright..
Signal-Detection theory: proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity
Subliminal perception: the registration of sensory input without conscious awareness Dancing people can be viewed as something else
Stanky STANK!!!! Sensory adaptation: gradual decline in sensitivity to prolonged stimulation Ex. Getting used to a nasty smell
Pathway to the Brain Stimulus: Light (form of electromagnetic radiation that travels as a wave) Amplitude: height of wave-brightness Wavelength: distance between peaks-hue Purity-saturation
Structures Cornea: protective cover Iris: colored ring of muscle, regulates amount of light Pupil: (black hole in center) Lens: focuses the light that falls on the retina
Retina: neural tissue lining that absorbs and processes light Rods: night and peripheral vision (humans have about 100-125 million) Cones: daylight and color vision (humans have about 6-6.4 million) Cones & rods activate bipolar cells. Fovea: tiny spot in center of the retina that only contains cones; visual acuity is greatest at this spot Optic disk: hole in the retina where the optic nerve exits the eye, a.k.a blind spot
Bipolar cells and ganglion cells: both receive neural signals Optic chiasm: point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain Optic nerve connects eye to the thalamus then to the visual cortex of the occipital lobe
PG135
Nearsightedness: close objects are seen clearly but distant objects appear blurry Farsightedness: distant objects are seen clearly but close objects appear blurry
It burns the eyeballs!!!!! Dark adaptation: process in which the eyes become more sensitive to light in low illumination Ex. Entering a movie theatre on a bright day pirates Light adaptation: process whereby the eye become less sensitive to light in high illumination Ex. When you leave the movie theatre
Lateral antagonism: occurs when neural activity in a cell opposes activity in surrounding cells
COLOR! Subtractive color mixing: works by removing some wavelengths of light, leaving less light than was originally there. Ex. Mixing yellow and blue to make green Additive color mixing: works by superimposing lights, putting more light in the mixture than exists in any one lights by itself Ex. If you shine red, green, and blue spotlights on a white surface Additive Subtractive
Trichromatic theory: 3 types of cones that detect red, blue, and green that are activated in different ways Color blindness: encompasses a variety of deficiencies in the ability to distinguish among classes
After images: a visual image that persists after a stimulus is removed
Reversible figure: a drawing that is compatible with two interpretations that can shift back and forth
NECKER CUBE! SCHRODER S STAIRCASE!
Feature analysis: process of detecting specific elements in visual input and assembling them into a more complex form Bottom up processing: add information together Phonetics C A.T Top down processing : we perceive by filling in the blanks (use background info) Ex. I w_nt to p_ss t_e t_st! Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
Gestalt Principles! Phi phenomenon: the illusion of movement created by visual stimuli in rapid succession Ex. Flip book Old cartoons consist of separate still pictures projected rapidly one after the other Figure and Ground: when you look at an image you have to decide what is in the background and what is in the foreground Ex. Again with the two faces or vase, you have to decide what is background and what is foreground
Gestalt cont.
Perceiving Depth! Depth perception: involves interpretation of visual cues that indicate how near or far away objects are Binocular cues: clues about distance bases on differing views of the two eyeballs. Retinal disparity Convergence Ex. Sausage fingers
Perceiving Depth Cont. - Monocular cues: clues about distance bases on the image in either eye alone - Motion parallax: involves images of objects at different distances moving across the retina at different rates - Pictorial depth cues: clues about distance that can be given in a flat picture Linear perspective Texture gradient Light and shadow Relative size Height in plane Interposition
Optical illusions: involve apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality Muller-Lyer illusion
This is just for fun!!
Impossible figure: objects that can be represented in two-dimensional pictures but cannot exists in three-dimensional space
The Auditory System! Stimulus: sound waves Amplitude: height of wave (loudness) Frequency: length of wave (pitch) Purity:Timbre (tone)
Pathway to the Brain!
Pinna: external part of ear funnels the sound Auditory canal: sound travels through Eardrum: sound hits and vibrates Ossicles: hammer, anvil, and the stirrup transmits vibrations to oval window
Cochlea: fluid-filled spiral tunnel that contains receptors Basilar membrane: holds the auditory receptors all along cochlea Auditory Nerve: sound travels through this to the thalamus then to the auditory cortex of the temporal lobe
Pitch Theories! Place theory: hair cells respond to different frequencies based on where they are located in the cochlea Frequency theory: rate at which the entire basilar membrane vibrates
Change Blindness! Mrs. Wilson go here and you will know what it is! Change blindness & selective http://viscog.beckman.uiuc.edu/grafs/demos/15.ht ml attention videos http://viscog.beckman.uiuc.edu/grafs/demos/10.html
The Gustatory System! TASTE
Stimulus: food! Taste buds on the papillae absorb 4 senses Sweet, salty, sour, bitter Flavor is a mix of taste and smell
The Olfactory System A good way to remember is that an old factory smells bad!!
Stimulus: chemicals emitted by substances in the air Olfactory bulb: gathers messages and sends them to the brain Receptors: Cilia Nerve fibers connect to amygdala/limbic system (emotion and memories) DOES NOT TRAVEL THROUGH THE THALAMUS
Kinesthetic Sense! It monitors the positions of the various parts of the body Information from muscles and joints keep track of your body Does this guy know where his feet are????
Vestibular Sense! This is a response to gravity and keeps you informed of your body s location in space Provides you with a sense of balance and equilibrium The 3 semicircular canals in the ear tell the body s orientation Agitated canals cause nausea and dizziness
I hope you enjoyed!! Class of 09!!!!!!!! Check out Skytopia.com http://www.skytopia.com/project/illusion/illusions.html#eclipse of Titan