Chapter 5: Sensation, Perception, and Attention
Chapter Review
Summarizing the Principles of Sensation, Perception, and Attention
How Do We Sense Our Worlds?1. Stimuli must be coded to be understood by the brain: Stimuli reaching the receptors are converted to neural impulses through the process of transduction.
2. Psychophysics relates stimulus to response: By studying how people respond to different sensory levels, scientists can determine thresholds and perceived change (signaldetection theory). Our sensory systems are tuned to adapt to constant levels of stimulation and detect changes in our environment.
What Are the Basic Sensory Processes?
3. In gustation, taste buds are chemical detectors: The gustatory sense uses taste buds to respond to the chemical substances producing basic sensations of sweet, sour, salty, and bitter. The amount and concentration of taste buds vary individually.
4. In smell, the nasal cavity gathers particles of odor: Receptors in the olfactory epithelium respond to chemicals and send signals to the olfactory bulb in the brain. Pheromones are particular chemical signals linked to physiological responses in animals.
5. In touch, sensors in the skin detect pressure, temperature, and pain: The haptic sense relies on tactile stimulation to activate receptors for temperature, sharp and dull pain, and other sensations. Neural "gates" in the spinal cord also control pain.
6. In hearing, the ear is a sound-wave detector: The size and shape of sound waves activate hair cells in the inner ear. The receptors respond depending on frequency of the sound waves, timing, and the location of the activated receptors. Having two ears allows us to locate the source of a sound.
7 In vision, the eye detects light waves: Receptors (rods and cones) in the retina detect different forms of light waves. The lens helps the eye focus the stimulation on the retina for near versus far objects. Color is determined by wavelengths of light activating certain types of cones, by the absorption of wavelengths by objects, or the mixing of wavelengths of light.
What Are the Basic Perceptual Processes?
8. Perception occurs in the brain: The primary auditory cortex handles hearing. Touch is handled by the primary somatosensory cortex. Vision results from a complex series of events in a variety of areas of the brain but primarily in the occipital lobe.
9. Object perception requires construction: By using the Gestalt principles of stimulus organization, we are able to perceive our world. We use cues about similarity, proximity, form, figure and background properties, and shading. Perception involves the dual processes: bottom-up (sensory information) and top-down (brain organization).
10. Depth perception is important for locating objects: The pattern of stimulation of an object on each of the two retinas (binocular) informs the brain about depth. Pictorial (monocular) cues use information from the appearance of objects relative to their surroundings to inform about depth, as well as relative motion.
11. Size perception depends on distance perception: Illusions of size can be created when the retinal size conflicts with the known size of objects in the visual field, such as with the Ames, Ponzo, and moon illusions.
12. Motion perception has both internal and external cues: Motion detectors in the cortex respond to stimulation. The perceptual system establishes a stable frame of reference and relates object movement to it. Intervals of stimulation of repeated objects give the impression of continuous movement.
13. Perceptual constancies are based on ratio relationships: Hermann von Helmholz felt that experience provides ratio information about objects in their surroundings to achieve constancy. James Gibson felt the information was a primary, evolutionarily based aspect of perception. The contemporary view is a blend of the two theories.
How Does Attention Help the Brain Manage Perceptions?
14. Visual attention is selective and serial: We process the elements and features of visual stimulus simultaneously. Studies of brain-injured patients reveal that different areas of the brain process different information.
15. Auditory attention allows selective listening: The cocktail party phenomenon demonstrates how we readily shift attention to relevant auditory information.
16. Selective attention can operate at multiple stages of processing: The debate on selective attention centers on when information is filtered or passed on for further processing.
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