Sensation and perception
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Sensation and Perception. Chapter 4. Defining Sensation and Perception. Sensation The detection of physical energy emitted or reflected by physical objects. It occurs when energy in the external environment or the body stimulates receptors in the sense organs. Perception

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Sensation and Perception

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Sensation and perception

Sensation and Perception

Chapter 4

Defining sensation and perception

Defining Sensation and Perception

  • Sensation

    • The detection of physical energy emitted or reflected by physical objects.

    • It occurs when energy in the external environment or the body stimulates receptors in the sense organs.

  • Perception

    • The process by which the brain organizes and interprets sensory information.

Sensation and perception

Ambiguous Figure

  • Colored surface can be either the outside front surface or the inside back surface

    • Cannot simultaneously be both

  • Brain can interpret the ambiguous cues two different ways

Sensation perception processes

Sensation & Perception Processes

  • Sense receptors

    • Specialized cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.

Sensory overload

Sensory Overload

  • Overstimulation of the senses.

  • Let’s play an observation game!

  • Can use selective attention to reduce sensory overload.

    • Selective attention

      • The focusing of attention on selected aspects of the environment and the blocking out of others.

      • Inattentional blindness

      • Cocktail-party effect

      • Change blindness

Measuring senses

Measuring Senses

  • Absolute threshold

  • Difference threshold

  • Signal-detection theory

Absolute threshold

Absolute Threshold

  • The smallest quantity of physical energy that can be reliably detected by an observer.

Absolute sensory thresholds

Absolute Sensory Thresholds

  • Vision:

    • A single candle flame from 30 miles on a dark, clear night

  • Hearing:

    • The tick of a watch from 20 feet in total quiet

  • Smell:

    • 1 drop of perfume in a 6-room apartment

  • Touch:

    • The wing of a bee on your cheek, dropped from 1 cm

  • Taste:

    • 1 tsp. Sugar in 2 gal. water

Pledge of allegiance

Pledge of Allegiance

  • I pledge allegiance

Sensation and perception

to the flag

Sensation and perception

  • of the United States of America

Sensation and perception

  • and to the republic

Sensation and perception

  • for which it stands

Sensation and perception

  • one nation under God

Sensation and perception

  • indivisible

Sensation and perception

  • with liberty

Sensation and perception

  • and justice for all

Sensation and perception


  • Each slide of the Pledge of Allegiance increased the font size. (28 to 45)

  • Did you notice?

Stimulus discrimination

Just Noticeable Difference (JND):

The smallest amount of change in a stimulus that can be detected half the time.

Weber’s Law

JND is proportional to the magnitude of the stimulus

The larger the stimulus the larger the change must be to be noticed!!

Light, Weight or Tone?

Stimulus Discrimination

Subliminal persuasion

Subliminal Persuasion

  • Derren Brown and Subliminal Advertising



  • Secret messages hidden in musical lyrics?

  • Let’s find out!!


Signal detection theory

Signal-Detection Theory

  • A psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process. (expectations, experience, anticipation)

Sensory adaptation and deprivation

Sensory Adaptation and Deprivation

  • Adaptation

    • The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious.

    • Prevents us from having to continuously respond to unimportant information.

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