Alternative transcript:

changes in the environment ■ 4. Thresholds Example: In an experiment, while a man provides directions to a construction worker, two experimenters rudely pass between them carrying a door. During this interruption, the original worker switches places with another person wearing different-colored clothing. The man, focused on giving their directions, does not notice the switch. 3. Transduction ● Our sensory systems perform an amazing feat: They convert one form of energy into another. Vision processes light energy. Hearing processes sound waves. All our senses: O receive sensory stimulation, often using specialized receptor cells. O transform that stimulation into neural impulses. O deliver the neural information to our brain. ● the process of converting one form of energy into another form that our brain can use ● Transduction = translation/ transformation a. Absolute thresholds O Gustav Fechner (1801-1887) German scientist and philosopher who studied the edge of our awareness of the faint stimuli, which he called their absolute thresholds-the minimum stimulation necessary to detect a particular light, sour pressure, taste, or odor 50 percent of the time. Sense Vision Hearing Smell Taste Touch O ■ Stimulus O Electromagnetic energy Sound waves Absolute Threshold for Humans Chemical substances in the air Chemical substances in saliva Pressure on the skin Subliminal Receptors Rods & cones in retina Hair cells of the inner ear Receptor cells in the nose Threshold A candle flame viewed from a distance of about 30 miles on a dark night O Signal detection theory ■ predicts when we will detect weak signals (measured as our ratio of "hits" to "false alarms" The ticking of a watch from about 20 feet away in a quiet room About one drop of perfume diffused throughout a small house Taste buds on the tongue | About 1 teaspoon of sugar dissolved in 2 gallons of water Nerve endings in the skin The wing of a fly falling on a cheek from a distance of about 0.4 inches assumes there is no single absolute threshold and that detect depends partly on a person's experience, expectations, motivation, and alertness • Example: stimuli you cannot consciously detect 50% of the time ■ below your absolute threshold The same person's reactions vary as circumstances change-as when creaking sounds trigger fear for someone home alone after watching a scary movie b. Difference thresholds O aka just noticeable difference (ind) O the minimum difference between two stimuli required for detection half the time. O That detectable difference increases with the size of the stimulus. O Example: If we listen to our music at 40 decibels, we might barely detect an added 5 decibels (the jnd). But if we increase the volume to 110 decibels, we probably won't then detect an additional 5-decibel change. Ernst Weber I In the late 1800s, he decreased this with a principle so simple and so widely applicable that we still refer to it as Weber's law: ● For an average person to perceive a difference, two stimuli must differ by a constant minimum percentage (not a constant amount) O The exact percentage varies, depending on the stimulus 5. Sensory Adaptation ● ● Diminished sensitivity as a consequence of constant stimulation When constantly exposed to an unchanging stimulus, we become less aware of it because our nerve cells fire less frequently. Example: O Put a bandaid on your arm, and after a while you don't sense it a. Context, Motivation, and Emotion Module 21 Influences on Perception 1. Perceptual Set - a set of mental tendencies and assumptions that affects, top-down, what we hear, taste, feel, and see. - influences how we interpret stimuli O O O The more intense the stimulus, the more change is needed to notice the difference ■ O Our immediate context, and the motivation and emotion we bring to a situation, also affect our interpretations Context ■ Imagine hearing a noise interrupted by the words "eel is on the wagon." Likely, you would actually perceive the first words as wheel. Given "eel is on the orange," you would more likely hear peel. In each case, the context creates an expectation that, top-down, influences our perception of a previously heard phrase. O O Example: ● Example: ● Two lights must differ in intensity by 8% Two objects must differ in weight by 2% ● Two tones must differ in frequency by 0.3% Emotion Motivation ■ Motives give us energy as we work toward a goal ■ Like context, they can bias our interpretations of neutral stimuli. ■ Example: Desirable objects, such as water bottle viewed by a thirsty person, seem closer than they really are. This perceptual bias energizes our going for it. ● When angry, people more often perceive neutral objects as guns. 2. ESP Perception without Sensation? - extrasensory perception (ESP) - parapsychology: the study of paranormal phenomena, including ESP and psychokinesis (telekinesis) - claims that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition a. Premonitions or Pretensions? O Given the countless events in the world each day, and given enough days, some stunning coincidences are bound to occur. By one careful estimate, chance alone would predict that more than a thousand times per day, someone on Earth will think of another person and then, within the next five minutes, learn of that person's death. O With enough time and people, the improbable becomes inevitable. b. Putting ESP to Experimental Test O Skeptics argue that (1) to believe in ESP, you must believe the brain is capable of perceiving without sensory input and (2) researchers have been unable to replicate ESP phenomena under controlled conditions. Module 22 Vision: Sensory and Perceptual Processing 1. Light energy and Eye structures a. The Stimulus Input: Light Energy O What we see as a visible light is but a thin slice of the wide spectrum of electromagnetic energy When you look at a bright red tulip, the stimuli striking your eyes are not particles of the color red, but pulses of electromagnetic energy that your visual system perceives as red. Light travels in waves, and the shape of those waves influences what we see. O O O O Short wavelength = high frequency (bluish colors); Long wavelength = low frequency (reddish colors) Light's wavelength ■ A light wave's amplitude, or height, determines its intensity-the amount of energy the wave contains. Intensity influences brightness. ■ Great amplitude (bright colors); Small amplitude (dull colors) b. The Eye the distance from one wave peak to the next. determines hue-the color we experience O Steps: 1) Light enters the cornea, which bends light to help provide focus. 2) The light passes through the pupil, a small adjustable opening. ● Surrounding the pupil and controlling its size is the iris-a colored muscle that dilates or constricts in response to light intensity; responds to your cognitive and emotional states. O Imagine a sunny sky and your iris will constrict, making your pupils smaller; imagine a dark room and it will dilate. 3) Light hits the transparent lens in the eyes 4) The lens focuses the light rays into an image on the retina-the light-sensitive inner surface of the eye, containing the receptor rods and cones. To focus the rays, the lens changes its curvature and thickness in a process called accommodation. O If the lens focuses the image on a point in front of the retina, you see near objects, but not distant objects-nearsightedness. 5) The light signal works their way from the retina to the visual cortex, which then informs the motor cortex, which then sends out orders to contract muscles ● 2. Information Processing in the Eye and Brain a. The Eye-To Brain Pathway O Steps with deeper explanation of what happens after light hits the retina: 1) Light goes through the retina's sparse outer layer of cells. 2) Reaching the back of the eye, there lies the retina's nearly 130 million buried receptor cells, the rods (retinal receptors that detect black, white, and gray, and are sensitive to movement; necessary for peripheral and twilight vision, when cones don't respond) and cones (retinal receptors that detect fine detail and give rise to color sensation; function in daylight or in well-lit conditions),-our eyes' light-sensitive photoreceptors-where the light energy trigger chemical changes. O 3) That chemical reaction would spark neural signals in nearby bipolar cells. 4) The bipolar cells activate neighboring ganglion cells, whose axons twine together like the stands of a rope to form the optic nerve-the nerve that carries neural impulses from the eye to the brain. ● The eye has a blind spot-an area with no receptor cells- where the optic nerve leaves the eye. Fovea - the retina's area of central focus which the cones cluster in and around; the spot where vision is the most detailed b. Color Processing O O Young-Helmholtz trichromatic (three-color) theory ■ I Hermann von Helmholtz and Thomas Young (an English physicist) ● the theory that the retina contains three different types of color receptors-one most sensitive to red, one to green, one to blue-which, when stimulated in combination, can produce the perception of color. Example: formed a hypothesis: The eye must have three corresponding types of color receptors. ● The retina has no separate receptors especially sensitive to yellow. But when red and green wavelengths stimulate both red-sensitive and green-sensitive cones, we see yellow. O Aftermirage ■ Physiologist Ewald Hering-a present-day von Helmholtz-noted, trichromatic theory leaves some parts of the color vision mystery unsolved ● formed another hypothesis: Color vision must involve two additional color processes, one responsible for red-versus-green, and one for blue-versus-yellow perception an impression of a vivid sensation (especially a visual image) retained after the stimulus has ceased Opponent-process theory ■ confirmed Hering's hypothesis ■ the theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision c. Feature Detection O David Hubel and Torsten Weisel (1979) O feature detectors: nerve cells in the brain's visual cortex that respond to specific features of the stimulus, e.g. shape, angle, or movement d. Parallel Processing O processing many aspects of a problem at once O the brain's natural mode of information processing for many functions Module 23 Visual Organization & Interpretation 1. Perceptual Organization a. Form Perception O figure-ground: the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground). O Grouping: the perceptual tendency to organize stimuli into coherent groups ■ Examples: ● Proximity: We group nearby figures together. O We see not six separate lines, but three sets of two lines b. Depth Perception O O O O ● ● Continuity: We perceive smooth, continuous patterns rather than discontinuous ones. O This pattern could be a series of alternating semicircles, but we could perceive it as two continuous lines-one wavy, one straight. Closure: We fill in gaps to create a complete, whole object. 2. The Ear O We assume that the circles on the left are complete but partially blocked by the (illusory) triangle. Add nothing more than little line segments to close off the circles and your brain stops constructing a triangle. the ability to see objects in 3D although the images strike the retina are 2D allows us to judge distance Visual cliff ■ Eleanor Gibson and Richard Walk (1960) ■ a laboratory device for testing depth perception in infants and young animals Binocular cues ■ a depth cue that depends on the use of two eyes ■ Convergence: the inward angle of the eyes focusing on a near object Retinal disparity: binocular cues for perceiving depth I c. Motion Perception O Phi phenomenon: an illusion of movement created when two or more adjacent lights blink on and off in quick succession d. Perceptual Constancy By comparing retinal images from the two eyes, the brain computes distance the greater the disparity (difference) between the two images, the closer the object O Monocular cues - depth cues available to each eye separately, e.g. interposition or linear perspective O a top-down process which perceives objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change O Color constancy: perceiving familiar objects as having consistent colors, even if changing illumination alters the wavelengths reflected by the object Brightness constancy (a.k.a. lightness constancy): perceive an object as having a constant brightness even as its illumination varies. O Size constancy: we perceive an object as having an unchanging size, even while our distance from it varies e. Perceptual Interpretation i. O Context governs our perceptions. Module 24 Hearing 1. The Stimulus Input: Sound Waves Experience and Visual Perception perceptual adaptation: the ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field. The height (amplitude) of sound waves determines their perceived loudness. The length (frequency) determines the pitch (high or low) we experience. O Long waves = low frequency = low pitch O Short waves high frequency=high pitch ● ● 3. Perceiving Loudness, Pitch, and Location a. Responding to Loud and Soft Sounds 2. Pain O If a hair cell loses sensitivity to soft sounds, it may still respond to loud sounds. b. Hearing Different Pitches O Steps: 1. Middle ear - a piston made of three tiny bones-the hammer (malleus), anvil (incus), and stirrup (stapes)-picks up the vibrations and transmits them to the cochlea, a snail-shaped tube in your inner ear. 2. Incoming vibrations then cause the cochlea's membrane-covered opening (the oval window) to vibrate. O This motion causes ripples in the hair cells lining its surface 3. The hair cell movements in turn trigger impulses in adjacent cells, whose axons converge to form the auditory nerve. 3. Taste 4. Auditory nerve carries the neural messages to your thalamus and then on to the auditory cortex in your brain's temporal lobe Sensorineural hearing loss: nerve deafness; hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves Conduction hearing loss: caused by damage to the mechanical system that conducts sound waves to the cochlea Module 25 The Other Senses 1. Touch ● 4. Smell ● place theory: in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated a. Understanding Pain O frequency theory: temporal theory; in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch b. Controlling Pain o placebo O distraction Touch sensations involve more than tactile stimulation O gate-control theory: the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. ■ The "gate" is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain gustation our sense of taste sweet, sour, salty, bitter, and umami olfaction: the sense of smell 5. Body Position & Movement ● kinesthesia: our movement sense-our system for sensing the position and movement of individual body parts ● vestibular sense: our sense of body movement and position that enables our sense of balance 6. Sensory Interaction ● ● the principle that one sense may influence another embodied cognition: the influence of bodily sensations, gestures, and other states on cognitive performance and judgements