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Chapter 3. Sensation and Perception. Sensation is the process in which we receive, transform, and process stimuli from the outside world to create sensory experiences of vision, touch, hearing, taste, smell and so on. There are actually 7 body senses, not just the 5 we normally think of.
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Chapter 3 Sensation and Perception
Sensation is the process in which we receive, transform, and process stimuli from the outside world to create sensory experiences of vision, touch, hearing, taste, smell and so on. There are actually 7 body senses, not just the 5 we normally think of. What is Sensation?
Sensory receptors- Specialized cells that detect sensory stimuli and convert them into neural impulses, which the brain uses to create the sensations of our senses. Absolute Threshold- The smallest amount of a given stimulus a person can sense. Sensation
Came up with the idea of difference threshold or just-noticeable difference. Difference Threshold- The minimal difference between 2 stimuli that people can reliably detect. Ernst Weber 1795-1878
The amount you must change a stimulus to detect a difference is given by a constant fraction or proportion. • Ex. Weber’s constant for noticing a difference in weight is 1/50 or 2% • If you were lifting a 50 lb. weight, you would probably not notice a difference unless the weight were increased or decreased by 2% (1 lb.). Weber’s Law
If you were lifting a 50 lb. weight, you would probably not notice a difference unless the weight were increased or decreased by 2% (1 lb.). But, if you were lifting a 200 lb. weight, the weight would have to be increased or reduced by 4 lbs. (2%) to notice a difference. Weber’s Law
Detection of a stimulus depends on these factors • The intensity of the stimulus • The level of background stimulus • Biological and psychological characteristics of the perceiver. Signal Detection Theory
Physical condition can play a role in Signal Detection • Sense of smell is more dull if your nose is stuffed or if you have a cold. • Alertness levels affect signal detection • Motivation: Walking down a dark alley, staying home alone (notice sounds). • Hunger: Aromas or TV commercials when you haven’t eaten in a while Signal Detection Theory
The process by which sensory receptors adapt to constant stimuli by becoming less sensitive to them. • Cold swimming water • Wristwatch, ring • Music • Odors ( i.e., men’s locker room) Sensory Adaptation
Perception- The process by which the brain interprets sensory information, turning it into meaningful representations of the external world. Through perception, our brain attempts to make sense of the mass of sensory stimuli that impinge on our sensory organs. Perception
Attention is the first step in perception. Through selective attention you limit your attention to certain stimuli while filtering out other stimuli. Selective attention prevents you from being flooded with extraneous information. Attention: Did you notice that?
We pay more attention to stimuli that are meaningful or emotionally significant. Motivational states, such as hunger or thirst, play important roles in attention. When we are hungry, we are more likely than when we’ve just eaten to pay attention to odors wafting out of a restaurant. Attention: Did you notice that?
Repeated exposure may increase attention to particular stimuli. On the other hand, exposure to a constant stimulus can lead us to become habituated, or accustomed, to a stimulus. Ex. The humming sound of an air conditioner Attention: Did you notice that?
Bottom-up Processing- The brain assembles specific features of shapes, such as angles and lines, to form patterns that we can compare with stored images we have seen before. Bottom-up processing may also be used to combine the individual elements of letters and words into recognizable patterns. Modes of Visual Processing: Bottom-Up Vs. Top-Down
Top-Down Processing- perceiving patterns as meaningful wholes- such as recognizing faces of people we know- without needing to piece together their components. Top-down is based on acquired experience and knowledge with patterns, but it is not perfect. Modes of Visual Processing: Bottom-Up Vs. Top-Down
People tend to group bits and pieces of sensory information into unitary forms or wholes. Gestalt psychologists described several principles of grouping, including proximity, similarity, continuity, closure, and connectedness. Gestalt Laws of Grouping
Proximity- the principle that objects that are near each other will be perceived as belonging to a common set. Gestalt Laws of Grouping
Similarity- The principle that objects that are similar will be perceived as belonging to the same group. Gestalt Laws of Grouping
Continuity- The principle that a series of stimuli will be perceived as representing a unified form. Gestalt Laws of Grouping
Closure- The perceptual principle that people tend to piece together disconnected bits of information to perceive whole forms. Gestalt Laws of Grouping
Connectedness- The principle that objects positioned together or moving together will be perceived as belonging to the same group. Gestalt Laws of Grouping
