Chapter 6 Detection of Stimuli Perception & recognition of patterns Perception of movement and depth Optical Illusions What is the softest noise you are able to hear? Absolute sensory threshold- intensity at which you can detect a stimulus 50% of time, lower threshold indicates ability to detect more faint stimuli Ability of stimulus to influence our behavior even when it is presented faintly or briefly along with such strong distracters that we do not perceive it consciously Overall, few research studies show that subliminal perception significantly affects behavior Studies show we DO unconsciously perceive subliminal info (p. 183), but effects on our behavior are not powerful (p. 182) How do we know what we are really looking at? The more intense the light is, the brighter the appearance of the object Brightness contrast- increase or decrease in an object?s apparent brightness because of the effects of objects around it Feature-detector -neuron in the visual system of the brain that responds to the presence of a certain simple feature, such as a horizontal line (i.e. recognizing letters of the alphabet) http://www.michaelbach.de/ot/mot_adaptSpiral/index.html Proof for feature detectors- if human cortex does contain feature detectors, then one type should become fatigued after we stare a while at the features that excite it (i.e. the waterfall illusion ? staring at a waterfall for a long time and then looking away makes things appear to flow upward). Gestalt psychology- an approach in psychology that seeks to explain how we perceive overall patterns Gestalt = German for ?overall pattern? or ?configuration? ?The whole is different than the sum of its parts? To perceive an object, you sometimes separate it from its background, which is called ?figure and ground? (an object and its background) An object that can be perceived in more than one way is referred to as a reversible figure REVERSIBLE FIG 1. REVERSIBLE FIG 2. There are different ways we organize individual parts of patterns so that we can make some sense out of them, otherwise we would be living in a world of nonsense? Principles of how we organize perceptions into meaningful wholes Proximity- tendency to perceive objects that are closer together as belonging to a group Similarity-tendency to perceive objects that resemble one another as belonging together Continuation- tendency to fill in gaps in an interrupted line Closure- tendency to imagine rest of an incomplete, familiar figure 5. Common fate- tendency to perceive objects as being part of the same group if they change or move in similar ways at the same time 6. Good figure- tendency to perceive simple, symmetrical figures ( i.e. familiar and geometrically sound shapes) Visual constancy- tendency to perceive objects as unchanging in shape, size, and color, despite variations in what actually reaches the retina Ex: when a friend walks away from us, their image on our retina becomes smaller, yet we perceive them as moving, not getting smaller STROBOSCOPIC Stroboscopic movement- an illusion of movement created by a rapid succession of stationary images (movies) Think about a strobe light= rapid succession of light Phi effect- illusion of movement created when 2 or more stationary lights separated by a short distance flash on and off at regular intervals Ex: Blinking vacancy lights at a motel Depth perception- perception of distance, enables us to experience the world in 3 dimensions Retinal disparity- difference in apparent position of an object as seen by left and right retinas (ex: finger experiment) Convergence- degree to which eyes turn to focus on a close object Binocular cues- visual cues that depend on the action of both eyes ( retinal disparity, convergence) Monocular cues- visual cues that are just as effective with one eye (depth perception) Optical illusion- misrepresentation of visual stimuli Ames room study Room is designed to look like normal rectangular room, though its true dimensions are quite different Not designed in right angles or designed to be looked at head on Moon Illusion - Why does the moon appear bigger at the horizon? Misestimation of sound source or intensity of sound, perceiving a sound as being closer or further away than it actually is Different than an auditory delusion or hallucination (hearing something that is not there) as in schizophrenia or related illness Things are not always what they seem?.be open-minded, okay? (people, places, psychology, etc?) Illusions are not hallucinations We use biology (our visual system) to help us sort perception out (visual cues), but remember we still need intuition to tell us what something is or is not, these things are not mutually exclusive systems Brightness contrast, subliminal perception, Gestalt laws of perception, feature detectors, visual constancy, perception of movement (stroboscopic movement, phi effect, etc), optical illusions Questions: 1-4, 10 Vocab: 1-8, 11,13,15,16
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