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Myers’ PSYCHOLOGY (6th Ed). Chapter 5 Sensation Introduction and the Eye James A. McCubbin, PhD Clemson University Worth Publishers. Fact vs. Falsehood. 1. On a clear, dark night we can see a candle flame 30 miles away.

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Myers’ PSYCHOLOGY (6th Ed)

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Myers’ PSYCHOLOGY(6th Ed)

Chapter 5


Introduction and the Eye

James A. McCubbin, PhD

Clemson University

Worth Publishers

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.

  • 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)

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

How do we get information?

  • Bottom-Up Processing

    • analysis that begins with the sense receptors and works up to the brain’s 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)

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


  • 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 bee’s 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)


  • 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 person’s

      • experience

      • expectations

      • motivation

      • level of fatigue



of correct












Intensity of stimulus


  • Subliminal

    • When stimuli are below one’s absolute threshold for conscious awareness


  • Weber’s 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

Eye Movement

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

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

The spectrum of electromagnetic energy

Great amplitude

(bright colors, loud sounds)

Short wavelength=high frequency

(bluish colors, high-pitched sounds)

Long wavelength=low frequency

(reddish colors, low-pitched sounds)

Small amplitude

(dull colors, soft sounds)

Physical Properties of Waves

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

Eye Anatomy

How Vision works

  • Accommodation- the process by which the eye’s 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

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


  • Normal Nearsighted Farsighted Vision Vision Vision

Retina’s 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

Retina’s 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 eye’s cones cluster

Receptors in the Human Eye




6 million

120 million

Location in




Sensitivity in

dim light



Color sensitive?



Vision- Receptors

Pathways from the Eyes to the Visual Cortex

Illusory Contours

Visual Information Processing

  • Parallel Processing

    • simultaneous processing of several aspects of a problem simultaneously

Visual Information Processing

  • Trichromatic (three color) Theory

    • Young and Helmholtz

    • three different retinal color receptors

      • red

      • green

      • blue

Color-Deficient Vision

  • People who suffer red-green blindness have trouble perceiving the number within the design


Visual Information Processing

Opponent-Process Theory- opposing retinal processes enable color vision






black white

white black

Opponent Process- Afterimage Effect

Visual Information Processing

  • Color Constancy

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

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