1、Sensation & PerceptionChapter 3Part IIWilliam G. HuittLast revised: May 2005Sensation and Perception Sensation The process through which the senses pick up visual, auditory, and other sensory stimuli and transmit them to the brain; sensory information that has registered in the brain but has not bee
2、n interpreted Perception The process by which sensory information is actively organized and interpreted by the brainPerceptionGestalt principles of perceptual organization Figure-ground Organization depends on what we see as figure (object) and what we perceive a ground (context). Similarity Objects
3、 that have similar characteristics are perceived as unit. Proximity Objects close together in space or time perceived as belonging together. Continuity We tend to perceive figures or objects as belonging together if they appear to form a continuous pattern. Closure We perceive figures with gaps in t
4、hem to be complete.Perception You can see a white vase as figure against a black background, or two black faces in profile on a white backgroundPerceptionPerception Perceptual constancy The tendency to perceive objects as maintaining stable properties (e.g., size, shape, brightness, and color) despi
5、te differences in distance, viewing angle, and lighting Size constancy Perceiving objects as being about the same size when they move farther away Shape constancy Perceiving objects as having a stable or unchanging shape regardless of changes in the retinal image resulting from differences in viewin
6、g anglePerceptionPerception Monocular depth cues Depth cues that can be perceived by only one eye Types of cues Interposition When one object partly blocks your view of another, you perceive the partially blocked object as farther away Linear perspective Parallel lines that are known to be the same
7、distance apart appear to grow closer together, or converge, as they recede into the distancePerception Monocular depth cues Types of cues Relative size Larger objects are perceived as being closer to the viewer, and smaller objects as being farther away Texture gradient Near objects appear to have s
8、harply defined textures, while similar objects appear progressively smoother and fuzzier as they recede into the distance Atmospheric perspective Objects in the distance have a bluish tint and appear more blurred than objects close at handPerception Monocular depth cues Types of cues Motion parallax
9、 When you ride in a moving vehicle and look out the side window, the objects you see outside appear to be moving in the opposite direction Objects seem to be moving at different speeds those closest to you appear to be moving faster than those in the distance Objects very far away, such as the moon
10、and the sun, appear to move in the same direction as the viewerPerception James Gibson Pointed out that our perceptions of motion appear to be based on fundamental, but frequently changing, assumptions about stability Our brains search for some stimulus in the environment to serve as the assumed ref
11、erence point for stability When youre driving a car, you sense the car to be in motion relative to the outside environmentPerception Depth perception The ability to see in three dimensions and to estimate distance Binocular depth cues Depth cues that depend on two eyes working together Convergence O
12、ccurs when the eyes turn inward to focus on nearby objects the closer the object, the greater the convergence Binocular disparity (or retinal disparity) Difference between the two retinal images formed by the eyes slightly different views of the objects focused onPerception Ambiguous figures Can be
13、seen in different ways to make different images Best known ambiguous figure is “Old Woman/Young Woman,” by E. G. BoringWhat do you see?Now what do you see?Copyright Allyn & Bacon 2005Perception Impossible figures Do not seem unusual at first Figures that cannot be builtPerceptionPerception Illusion
14、A false perception of actual stimuli involving a misperception of size, shape, or the relationship of one element to anotherPerceptionl Mller-Lyer Illusion The two lines above are the same length, but the diagonals extending outward from both ends of the lower line make it look longer than the upper
15、 lineInfluences on Perception Bottom-up processing Information processing in which individual components or bits of data are combined until a complete perception is formed Top-down processing Application of previous experience and conceptual knowledge to recognize the whole of a perception and thus
16、easily identify the simpler elements of that wholeInfluences on PerceptionInfluences on PerceptionInfluences on Perception Perceptual set An expectation of what will be perceived, which can affect what actually is perceived David Rosenhan David Rosenhan and some of his colleagues were admitted as pa
17、tients to various mental hospitals with “diagnoses” of schizophrenia Once inside, they acted normal but the staff members only saw what they expected to see and not what was actually occurring The real patients were the first to realize that the psychologists were not really mentally illInfluences o
18、n Perception Inattentional blindness The phenomenon in which we miss an object in our field of vision because we are attending to anotherInfluences on Perception Simons and his colleagues Showed participants a videotape of a basketball game in which one team is uniformed in white and the other in bl
19、ack Instructed them to count how many times the ball was passed from one player to another either on the white or black team About a third of participants typically fail to later recall the presence on the screen of even extremely incongruent stimuli (e.g., a man dressed in a gorilla costume) under such conditionsInfluences on Perception Social perception Facial expressions, the visual cues for emotional perception, often take priority over the auditory cues associated with a persons speech intonation and volume, as well as the actual words spoken
