Myers

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Myers PSYCHOLOGY (6th Ed)

• Chapter 5
• Sensation
• Introduction and the Eye
• James A. McCubbin, PhD
• Clemson University
• Worth Publishers

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Fact vs. Falsehood

• 1. On a clear, dark night we can see a candle
  flame 30 miles away.
• 2. Advertisers are able to shape our buying
  habits through subliminal messages.
• 3. Constant eye movement prevents our vision
  from being seriously disrupted.
• 4. The retina of the eye is actually a piece of
  the brain that migrates to the eye during early
  fetal development.
• 5. If we stared at a green square for a while
  and then look at a white sheet of paper, we see
  red.
• 6. People who live in noisy environments are
  more likely to suffer from high blood pressure,
  anxiety, and feelings of helplessness.
• 7. Blind musician are more likely than sighted
  ones to develop perfect pitch.
• 8. Touching adjacent cold and pressure spots
  triggers a sense of wetness.
• 9. People who are born without the ability to
  feel pain usually die by early adulthood.
• 10. Without their smell, a cup of coffee may be
  hard to distinguish from a glass of red wine.

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• Sensation
• a process by which our sensory receptors and
  nervous system receive and represent stimulus
  energy (information from our environment)
• Perception
• a process of organizing and interpreting sensory
  information, enabling us to recognize meaningful
  objects and events (what we do with the sensory
  information we receive)

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• Our sensory and perceptual processes work
  together to help us sort out complex processes

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How do we get information?

• Bottom-Up Processing
• analysis that begins with the sense receptors and
  works up to the brains integration of sensory
  information (body to brain)
• Top-Down Processing
• information processing guided by higher-level
  mental processes
• as when we construct perceptions drawing on our
  experience and expectations (brain to body)

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Basic Principles

• Psychophysics
• study of the relationship between physical
  characteristics of stimuli and our psychological
  experience of them
• Light- brightness
• Sound- volume
• Pressure- weight
• Taste- sweetness

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Thresholds

• Absolute Threshold
• minimum stimulation needed to detect a particular
  stimulus 50 of the time
• vision candle flame at 30 miles on a clear dark
  night
• Hearing the ticking of a watch 20 ft away
• Sense a bees wing falling 1 cm onto our cheek
• Smell a drop of perfume in a 3 room apartment
• Taste 1 tsp of sugar in 2 gall of water
• Difference Threshold
• minimum difference between two stimuli required
  for detection 50 of the time
• just noticeable difference (JND)

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Thresholds

• Signal Detection Theory
• predicts how and when we detect the presence of a
  faint stimulus (signal) amid background
  stimulation (noise)
• assumes that there is no single absolute
  threshold
• detection depends partly on persons
• experience
• expectations
• motivation
• level of fatigue

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Thresholds

• Subliminal
• When stimuli are below ones absolute threshold
  for conscious awareness

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Thresholds

• Webers Law- to perceive as different, two
  stimuli must differ by a constant minimum
  percentage
• light intensity- 8
• weight- 2
• tone frequency- 0.3
• Sensory adaptation- diminished sensitivity as a
  consequence of constant stimulation

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Eye Movement
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How does Vision work?

• Transduction
• conversion of one form of energy to another
• in sensation, transforming of stimulus energies
  into neural impulses
• Wavelength
• the distance from the peak of one wave to the
  peak of the next

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What color is it?

• Hue
• dimension of color determined by wavelength of
  light
• Intensity
• amount of energy in a wave determined by
  amplitude
• brightness
• loudness

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The spectrum of electromagnetic energy
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Physical Properties of Waves
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Physiology of the Eye

• Pupil- adjustable opening in the center of the
  eye
• Iris- a ring of muscle that forms the colored
  portion of the eye around the pupil and controls
  the size of the pupil opening
• Lens- transparent structure behind pupil that
  changes shape to focus images on the retina

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Eye Anatomy
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How Vision works

• Accommodation- the process by which the eyes
  lens changes shape to help focus near or far
  objects on the retina
• Retina- the light-sensitive inner surface of the
  eye, containing receptor rods and cones plus
  layers of neurons that begin the processing of
  visual information

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Vision problems

• Acuity- the sharpness of vision
• Nearsightedness (myopia)- condition in which
  nearby objects are seen more clearly than distant
  objects because distant objects in front of
  retina
• Farsightedness (presbyopia)- condition in which
  faraway objects are seen more clearly than near
  objects because the image of near objects is
  focused behind retina

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Vision

• Normal Nearsighted Farsighted
  Vision Vision Vision

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Retinas Reaction to Light- Receptors

• Rods
• peripheral retina
• detect black, white and gray
• twilight or low light
• Cones
• near center of retina
• fine detail and color vision
• daylight or well-lit conditions

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Retinas Reaction to Light

• Optic nerve- nerve that carries neural impulses
  from the eye to the brain
• Blind Spot- point at which the optic nerve leaves
  the eye, creating a blind spot because there
  are no receptor cells located there
• Fovea- central point in the retina, around which
  the eyes cones cluster

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Vision- Receptors
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Pathways from the Eyes to the Visual Cortex
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Illusory Contours
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Visual Information Processing

• Parallel Processing
• simultaneous processing of several aspects of a
  problem simultaneously

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Visual Information Processing

• Trichromatic (three color) Theory
• Young and Helmholtz
• three different retinal color receptors
• red
• green
• blue

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Color-Deficient Vision

• People who suffer red-green blindness have
  trouble perceiving the number within the design
• http//www.colblindor.com/coblis-color-blindness-s
  imulator/

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Visual Information Processing

• Opponent-Process Theory- opposing retinal
  processes enable color vision
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black

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Opponent Process- Afterimage Effect
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Visual Information Processing

• Color Constancy
• Perceiving familiar objects as having consistent
  color, even if changing illumination alters the
  wavelengths reflected by the object