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Sensation. Basic Concepts Characteristics of Sensory Systems The Visual System. Sensation. The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. (from text)
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Sensation • Basic Concepts • Characteristics of Sensory Systems • The Visual System
Sensation • The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. (from text) • In other words…The process of converting physical stimuli (light, sound, heat, pressure, etc…) into the language of the brain (action potentials & neurotransmitter release). • Also known as “transduction” • Strongly associated with bottom-up processing: analysis strongly shaped by sensory receptors.
Important Thresholds • Absolute Threshold: The smallest possible amount of a stimulus that can be detected half (50%) of the time. • Difference Threshold: The smallest possible difference between two stimuli that can be detected half (50%) of the time.
Some Questions to Consider. • Would you notice a change of $10,000 in your bank account? • Would everyone notice a change of $10,000 in their bank accounts?
Weber’s Law • The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant minimum amount).
Two Theories of Color Vision • Trichromatic Theory • blue, green, & red sensors • Opponent Process Theory • Blue-yellow, red-green, & black-white sensors
Some Unusual Quotes • “N is sort of… rubbery… smooth, L is sort of the consistency of watery paint… Letters also have vague personalities, but not as strongly as numerals do.” • “The letter A is blue, B is red, C is a kind of light gray, D is orange…” • “I hear a note by one of the fellows in the band and it’s one color. I hear the same note played by someone else and it’s a different color. When I hear sustained musical tones, I see just about the same colors that you do, but I see them in textures.” • “Basically, I taste words.”
Synesthesia • The perceptual experience of one sense that is evoked by another sense. • For the typical person: A B C D E • For someone with synesthesia: ABCDE
Perception • Review • Important Points about Perception • Object Perception • Depth & Distance Perception • Illusions
I. Review • Sensation: The process of converting physical stimuli into the language of the brain. • Example: converting photons of light into nerve impulses • Perception: The process of integrating, organizing, and interpreting sensory information. • Example: recognizing the pattern of light that corresponds to the face of a friend
Bottom-Up versus Top-Down • Bottom-Up Processing: Information processing that is strongly shaped by adding up the inputs of sensory receptors. • Top-Down Processing: Information processing that is strongly shaped by higher level mental processes (such as expectations or beliefs).
II. Important Points about Perception • Perceptual systems often misperceive the world • Perceptions are strongly influenced by context • Perceptions are strongly influenced by beliefs and expectations
Gestalt Laws of Perceptual Grouping • We perceive as belonging together objects that.. • are close to each other (proximity). • are similar to each other (similarity). • are physically touching each other (connectedness). • form continuous lines, curves, or patterns (continuity/good continuation) • We also tend to perceive objects as more complete than they really are (closure).
Depth Cues • Monocular depth cues only require one eye • Binocular depth cues require two eyes
