Chapter 4: Sensation & Perception

Chapter 4: Sensation & Perception

30?

ThEcOwgAvecOla TheCowGaveCola rat eht saw tac eht The cat saw the rat The cat was the rat The cat was the tar

Stimulation of sensory receptors and the transmission of sensory information to CNS Automatic Results from energy like light and sound or presence of chemicals Sensation

Perception Psychological process through which we interpret sensory stimulation Reflects learning, expectations, and attitudes

Sensory Thresholds Absolute Threshold Weakest amount of a stimulus that can be sensed Difference Threshold The minimum amount of difference that can be detected between two stimuli

Sense Stimulus Receptors Threshold Vision Electromagnetic Energy Rods & Cones in the retina A candle flame viewed from a distance of about 30 miles on a dark night Hearing Sound waves Hair cells of the inner ear The ticking of a watch from 20 ft away in a quiet room Smell Chemical substances in the air Receptor cells in the notes 1 drop of perfume diffused throughout a small house Taste Chemical substances in saliva Taste buds on the tongue 1 teaspoon of sugar dissolved in 2 gallons of water Touch Pressure on the skin Nerve endings on the skin The wing of a fly falling on a cheek from.4 inches away

Signal-Detection Theory Method of distinguishing sensory stimuli that takes into account not only their strengths but also the setting, your physical state, mood, and attitudes Also considers psychological factors like motivations, expectations, learning

Sensory Adaptation Sensory systems adapt to a changing environment We become more sensitive to weak stimuli and less sensitive to unchanging stimuli

Section 2: Vision

Vision Light electromagnetic energy Described in wavelengths Colors on spectrum from longest to shortest (RoyGBv)

The Eye Light enters eye & is projected onto a surface Amount of light that enters determined by size of opening (pupil) Pupil size sensitive to light & emotion, automatically adjusts

Retina Sensitive surface in eye that acts like the film in a camera; consists of neurons, not film Photoreceptors Neurons in retina that send message to brain

The Blind Spot Area where optic nerve leaves the eye Eyes unable to register when light hits blind spot If we didn t have this, no visual input would reach the brain through the optic nerve for interpretation

Dark & Light Adaptation Dark Adaptation adjustment to lower lighting Continues to improve up to 45 minutes Bright Light Adaptation happens much quicker Takes only a minute or two

Visual Acuity Sharpness of vision Determined by ability to see visual details in normal light Near-sighted have to be close to an object to make out details Far-sighted Have to be further away than someone with normal vision to see it clearly As we age, our lenses get brittle, more difficult to focus...we become far-sighted

Two kinds of photoreceptors: 1. Rods Sensitive only to the brightness of light Allow us to see in black and white 2. Cones Provide color vision Less sensitive to light than rods Rods & Cones

Color Vision People with normal color vision see any color in the spectrum of visible light Complementary colors are across from one another When mixed together, form gray (as light)

Cones & Color Vision Certain cones are sensitive to blue, green, or red When more than one kind of cone is stimulated at the same time, we perceive other colors of the spectrum

Afterimages Afterimage of a color is its complementary color Happens when you ve stared at a color for a while and then it s removed

Color Blindness Partially or totally unable to distinguish color due to an absence of, or malfunction in the cones Total color blind sensitive only to light and dark and see the world as black and white (very rare) Partial color blindness common especially redgreen colorblindness

Color Blindness

The Stroop Effect Illustrates how difficult it is to ignore some kinds of stimuli You were receiving two stimuli, the color and the word, which compete and slow you down when you try to name the color http://www.youtube.com/watch?v=tpge6c3ic 4g&safe=active

Section 3: Hearing

Pitch - how high or low the sound is Timbre - complexity of a sound Intensity how loud a sound is Sound

Loudness Loudness of a sound determined by the height, or amplitude, of sound waves The higher the amplitude of the wave, the louder the sound Loudness measured in decibels (db)

The Ear Shaped to capture sound waves, to vibrate with them, and transmit sound to the brain

Outer Ear Eardrum thin membrane that vibrates when sounds strike it As it vibrates, it transmits sound to three small bones in the middle ear:

Middle Ear Hammer, anvil, stirrup These bones begin to vibrate and transmit sound to the inner ear

Inner Ear Cochlea bony tube that contains fluids & neurons that move in response to the vibrations of the fluids Movement generates neural impulses that are transmitted to the brain via the auditory nerve

Deafness Conductive Deafness Damage to the middle ear Amplifies sound People can t hear sounds loud enough Helped by hearing aids Sensorineural Deafness Damage to the inner ear Usually the cochlea Cochlear implants can help

Section 4: Other Senses

Smell Odors detected by receptor neurons high in each nostril Receptors send info to brain via the olfactory nerve Adapts quickly Without it, we wouldn t be able to taste as much

Taste Sweet, sour, salty, bitter, umami Flavor depends on odor, texture, temperature, and taste Sensed through receptors on taste buds Taste cells reproduce rapidly (within a week) Rare to completely lose sense of taste

Skin Senses Touch a combination of pressure, temperature, and pain 1. Pressure Different parts of body more sensitive than others 2. Temperature Receptor neurons just beneath the skin 3. Pain Pain receptors greater in certain areas Gate Theory: only a certain amount of information can be processed by nervous system at a time

Body Senses Vestibular Sense Keeps balance Kinesthesis Informs us about the position and motion of our body

Extrasensory Perception Occurs without the use of known sensory processes 1. Telepathy 2. Precognition 3. Clairvoyance 4. Psychokinesis

Section 5: Perception

Tendency to perceive a complete or whole figure even when there are gaps in what your senses tell you Closure

The Ebbinghaus illusion is an optical illusion of relative size perception. In the bestknown version of the illusion, two circles of identical size are placed near to each other and one is surrounded by large circles while the other is surrounded by small circles; the first central circle then the second central circle. Read more at smaller than the second central circle. Read

The impossible cube or irrational cube is an impossible object that draws upon the ambiguity present in a Necker cube illustration. An impossible cube is usually rendered as a Necker cube in which the edges are apparently solid beams. This apparent solidity gives the impossible cube greater visual ambiguity than the Necker cube, which is less likely to be perceived as an impossible object. The illusion plays on the human eye s interpretation of twodimensional pictures as three-dimensional objects.

Figure-Ground Perception Perception of figures against a background What we perceive as the figure and what we perceive as the background influence our perception

The café wall illusion is an optical illusion, first described by Doctor Richard Gregory. He observed this curious effect in the tiles of the wall of a café at the bottom of St Michael s Hill, Bristol. This optical illusion makes the parallel straight horizontal lines appear to be bent. To construct the illusion, alternating light and dark bricks are laid in staggered rows. It is essential for the illusion that each brick is surrounded by a layer of mortar (the grey in the image). This should ideally be of a color in between the dark and light color of the bricks.

The Bezold Effect is an optical illusion, named after a German professor of meteorology, Wilhelm von Bezold (1837-1907), who discovered that a color may appear different depending on its relation to adjacent colors. In the above example, the red seems lighter combined with the white, and darker combined with the black.

A blivet, also known as a poiuyt, is an undecipherable figure, an optical illusion and an impossible object. It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.

Other Rules of Organization Similarity People think of similar objects as belonging together Proximity - nearness of some of the lines to each other Continuity we prefer to see smooth, continuous patterns, not disrupted ones Law of Common Fate perceive objects that are moving together as belonging together

Perception of Movement To see movement, humans must see an object change its position relative to other objects Stroboscopic Motion Illusion of movement is produced by showing the rapid progression of images or objects that are not moving at all

The Jastrow illusion is an optical illusion discovered by the American psychologist Joseph Jastrow in 1889. In this illustration, the two figures are identical, although the lower one appears to be larger. Read more at

In this figure the black lines seem to be unparallel, but in reality they are parallel. The shorter lines are on an angle to the longer lines. This angle helps to create the impression that one end of the longer lines is nearer to us than the other end. This is very similar to the way the Wundt illusion appears. It may be that the Zöllner illusion is caused by this impression of depth. Read more at

One type of motion illusion is a type of optical illusion in which a static image appears to be moving due to the cognitive effects of interacting color contrasts and shape position. To properly view this effect, click the image above to see the full sized version. Read more at

Stare at four dots for 30-40 seconds Look away at something smooth and all one color Blink eyes a few times What do you see?

Can you find the 9 figures hidden in the image?

Optical Word Illusion IT DEOSN'T MTTAER IN WAHT OREDR THE LTTEERS IN A WROD ARE, THE OLNY IPRMOATNT TIHNG IS TAHT THE FRIST AND LSAT LTTEER BE AT THE RGHIT PCLAE. THE RSET CAN BE A TOATL MSES AND YOU CAN SITLLRAED IT WOUTHIT PORBELM. TIHS IS BCUSEAE THE HUAMN MNID DEOS NOT RAED ERVEY LTETER BY ISTLEF, BUT THE WROD AS A WLOHE.

Perceptual Constancies Size object remains same size no matter how far away the object is Color objects keep their color even though different light might change the appearance of the color Brightness object the same brightness even when the intensity of the light around it changes Shape knowledge that an item has only one shape

Depth Perception Monocular Cues for Depth Need only one eye to be perceived Illusion of 3-D on two-dimensional surfaces Cause certain objects to appear more distant than others

Depth Perception Binocular Cues for Depth both eyes needed Retinal Disparity Images slightly different because they re seen differently in each eye Amount of disparity helps us determine depth Convergence When we try to maintain a single image of an approaching figure, our eyes move inward, or converge The closer we feel our eyes moving toward one another, the nearer the object