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The Stroop Effect (1)

The Stroop Effect (1). Red Blue Green Black Green Blue. The Stroop Effect (2). Green Red Blue Black Blue Red. Definitions. Sensation: The process of stimulating receptors Perception: Interpretation & selection of sensory input. The Retina.

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The Stroop Effect (1)

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  1. The Stroop Effect (1) Red Blue Green Black Green Blue

  2. The Stroop Effect (2) Green Red Blue Black Blue Red

  3. Definitions • Sensation: The process of stimulating receptors • Perception: Interpretation & selection of sensory input

  4. The Retina Made of about 107 million transducers: 100 million rods 7 million cones

  5. Rods • Mostly in the periphery • More light sensitive • Detect light and dark • Insensitive to red • Take 20-30 minutes to fully adapt to darkness

  6. Cones • Mostly in the fovea • Less light sensitive • Detect colors • Have best detail vision • Adapt fully to darkness in 2-3 minutes

  7. The Young-Helmholtz trichromatic theory:

  8. The Opponent Process Theory Cells are connected so as to place sensations of: • red in opposition to green • blue in opposition to yellow • black in opposition to white

  9. Color Vision • The trichromatic theory explains perception at the receptor level • The opponent process theory explains it at higher brain levels

  10. Seeing Afterimages In the following slide, fix your eyes on the dot in the center of the flag

  11. Lateral Inhibition • Cells in the retina are connected laterally by amacrine cells • Works to enhance contrasts

  12. Lateral Inhibition See the glowing white spots where the black lines cross?

  13. Ear Structures

  14. Ear Structures • Pinna: The external ear. Amplifies sound. Funnels energy to the middle ear. • Typanic Membrane (eardrum):Moves in response to sound waves. Converts sound energy to mechanical energy . • Ossicles:The hammer (maleus), anvil (incus), & stirrup (stapes). Transmit & amplify motion of eardrum

  15. Ear Structures • Cochlea: A fluid-filled chamber. Hair cells are attached to the basilar membrane . Converts mechanical energy to neural impulses. • Bone Conduction: Sound is also transmitted to the cochlea through contact with skull bones. This is why your voice sounds odd in recordings

  16. Hearing Sound Attributes • Pitch: determined by frequency • Loudness: determined by amplitude • Timbre: Complexity of the sound (number of component waves involved in it)

  17. Sound Waves

  18. Hearing Loss Hair cells, once lost, do not regenerate Even some children's toys can cause permanent hearing loss

  19. Hearing Loss Usually caused by continuous exposure to excessive noise The louder the noise, the less exposure needed

  20. Chemical Senses • Consist of smell & taste • Evoke memories, emotions • Humans vary greatly in chemical sensitivity

  21. Olfaction (Smell) • Senses vaporized molecules • Consists of 10 million rods embedded in the olfactory epithelium

  22. Olfaction (Smell) • Olfactory Bulbs: Matchstick-sized; Integrate signals from the olfactory rods, send them on to the brain • Turbinate Bones: Filter out dust and warm incoming air. Protect the olfactory epithelium. • Olfactory Rods: There are more than 100 different types. Each responds to different chemicals

  23. Smell Sensitivity • Sense of smell varies among animals • Dogs have 200 million olfactory rods, spread out in a much bigger nose • Humans differ greatly in ability to detect smells • The most sensitive people are 20 times more sensitive than the least

  24. Taste Buds The least numerous sensory receptors (humans have only about 10,000)

  25. Taste • Involves only 4 sensations: Sweet, sour, salty, bitter • Most of what we consider taste is actually smell • Texture is very important in enjoyment of food • People love fats for the smooth feeling they give food (most are tasteless)

  26. Taste Changes • There are no taste buds in the center of the tongue • Taste buds constantly replaced (like olfactory rods) • Taste sensitivity changes very little with age • Enjoyment of food among the aged is reduced by loss of sense of smell

  27. Somasthetic Senses • Kinesthetic sense: A moving sense • Vestibular sense: Being oriented • Touch: Feeling well • Temperature

  28. Skin Senses • The largest sensory apparatus, involves heat, cold, pressure, pain • Sensitivity varies throughout the body, reflected in the amount of brain devoted to each section of skin • The hands & face predominate

  29. Pain • Important for survival • Motivates us to protect the body, tend injuries, rest, seek medical help. • Gate Theory: • Suggests an area in the spinal cord where fast-conducting nerve fibers can block the messages of small, slow conducting fibers. • Suggests humans can block pain even when severely injured • Explains why the badly injured may not even notice an injury

  30. Endorphins • Slow firing of pain neurons • Accupuncture & placebos work through endorphin release • "Runner's high" involves endorphin production • Can be blocked by endorphin-blocking drugs

  31. Body Senses • Kinesthetic Sense • Knowledge of the position and motion of body parts. • Driven by receptors in muscles, joints, and ligaments • Vestibular Sense • Involves the semicircular canals & the vestibular sacs • Senses acceleration, not uniform motion • Motion sickness arises when vision and the vestibular sense give rise to different messages

  32. Subliminal Persuasion • Influence by messages that are below your level of awareness Ex: taped messages that are below auditory level • Double-blind studies have found little support for the efficacy of subliminal persuasion tapes (See the following example.)

  33. Subliminal Persuasion • Example: In one study, subjects were given audio tapes labeled for weight loss. • Half were given actual weight loss tapes • Half were given smoke-ending tapes • Results: The tapes with subliminal anti-smoking messages were just as effective as those with weight-loss messages. The label mattered, not the messages.

  34. Extra-Sensory Perception • Telepathy: Detecting others' thoughts • Clairvoyance: Knowing things that can't be sensed • Precognition: Predicting the future • Psychology is concerned with evidence • Evidence of psychic ability under controlled conditions is lacking Consider this: If you could read minds, couldn't you find something more worthy (and profitable) for your talent than to do cheap parlor tricks?

  35. Definitions-Psychophysics • Absolute Threshold: The point where you can tell the stimulus is there vs. not there 50% of the time • Difference Threshold: The smallest change in the stimulus that is just detectable 50% of the time

  36. Psychophysics: A World of Experience • Detecting signals • Signal detection theory • Sensitivity • Bias

  37. Intermediate Vision • Perceptual organization • Figure • Ground

  38. Figure-Ground We organize the world so some parts of a stimulus appear to stand out (figure) in front of other parts (ground)

  39. Gestalt Principles • The whole is greater than the sum of its parts. • A group of sensory elements forms something new that is greater than itself • Figure-Ground • Similarity • Proximity • Good Continuation • Closure • Simplicity

  40. Similarity • We group things that are similar in color, shape, etc. into single units and see them as belonging together • Note in the following example how similarity alters our perception of the stimulus as rows vs. columns of circles

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