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Sensation and Perception. Unit 4A O lny srmat poelpe can raed this.docx. Unit Overview. Sensing the World: Some Basic Principles Vision Hearing Other Senses Perceptual Organization Perceptual Interpretation Is there Extrasensory Perception?.
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Sensation and Perception Unit 4A O lnysrmatpoelpe can raed this.docx
Unit Overview • Sensing the World: Some Basic Principles • Vision • Hearing • Other Senses • Perceptual Organization • Perceptual Interpretation • Is there Extrasensory Perception? Click on the any of the above hyperlinks to go to that section in the presentation.
1. What are Sensation and Perception? What do we mean by bottom up processing and top-down processing? • Sensation the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. • Perception the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events • Are one continuous process • “ We perceive the world not exactly as it is, but as it is useful for us to perceive it ”
Introduction • Bottom-up processing = starts at our sensory receptors and works up to the brain • No Prior Knowledge • Top-down processing = we construct perceptions drawing on experience and expectations. • Prior Knowledge, stereotyping
The Forrest Has Eyes • Bottom up processing : we receive sensory information on the horses and riders in the painting • Top down processing: we perceive faces in the forests and rivers based on our experience and expectations of what faces look like.
2. How are we affected by selective attention? Selective Attention = the focusing of conscious awareness on a particular stimulus. - Cocktail Party Effect - Our ability to focus on a conversation in a crowded and loud environment. - Cell Phone use and Car Accidents : - Texting and Driving Statistics
Inattentional blindness = failing to see visible objects when our attention is directed elsewhere. Change Blindness = failing to notice a change Selective Attention Test
3. What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence? • Psychophysics = the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them. • Absolute threshold = the minimum stimulation necessary to detect a particular stimulus 50% of the time.
Signal detection theory = a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and altertness. • Examples: • In war, failure to detect an intruder could be fatal. So soldiers on guard, who are responsible for others lives, might be more likely to detect an almost imperceptible noise, because they will be more focused. • TSA Scanners monitoring bags, Nurses monitoring ICU patients, Air Traffic Controllers watching the radar. • How soon would you notice an incoming text if (1) you are expecting a particular one, (2) it is important that you detect it, (3) you are alert.
Subliminal = below one’s absolute threshold for conscious awareness. • Priming = the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.
Difference threshold (JND) = the minimum difference between two stimuli required for detection. We experience the difference threshold as a just noticeable difference. • Weber’s law = the principle that, to be perceived as different, two stimuli must differ by a constant percentage (rather than a constant amount).
4. What is the function of Sensory Adaptation? • Sensory adaptation = diminished sensitivity as a consequence of constant stimulation. • After constant exposure to stimulus, our nerve cells fire less frequently. • Examples: • You enter a neighbors living room and smell a musty odor. You wonder how they can stand it, but after a few minutes you no longer notice it. • Move your watch up your wrist by one inch. You will feel it but only for a few moments.
So why if we stare at an object without flinching it doesn’t vanish from sight? • Our eyes are constantly moving, flitting from one spot to another enough to guarantee that stimulation continuously changes.
What if we could stop our eyes from moving? • Psychologists have devised an instrument that is a miniature projector attached to a contact lens. When the eye moves, so does the image. So the stimulus is always the same. • At first we would see the full picture but it would shift with time
Short Response • 1. What are Sensation and Perception? What do we mean by bottom up processing and top-down processing? • 2. How are we affected by selective attention? • 3. What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence? • 4. What is the function of Sensory Adaptation?
