Sensation and perception

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Sensation and perception
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Definitions

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

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Our Senses

• Vision
• Hearing
• Taste
• Smell
• Touch

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Specific nerve energies

• Different sensory modalities exist because
  signals received by the sense organs stimulate
  different nerve pathways leading to different
  areas of the brain.
• Synesthesia
• A condition in which stimulation of one sense
  also evokes another.

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Absolute threshold

• The smallest quantity of physical energy that can
  be reliably detected
• Vision
• A single candle flame from 30 miles on a clear
  night
• Hearing
• The tick of a watch from 20 feet in total quiet
• Smell
• One drop of perfume in a 6-room apartment
• Touch
• The wing of a bee on the cheek, dropped from 1 cm
• Taste
• One teaspoon of sugar in 2 gallons of water

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Difference threshold

• The smallest difference in stimulation that can
  be reliably detected by an observer when two
  stimuli are compared.
• Also called the Just Noticeable Difference (JND).

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Sensory adaptation and deprivation

• Adaptation
• The reduction or disappearance of sensory
  responsiveness when stimulation is unchanging or
  repetitious.
• Prevents us from having to respond continuously
  to unimportant information.
• Deprivation
• The absence of normal levels of sensory
  stimulation.

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Sensory overload

• Over-stimulation of the senses.
• 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.

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What we see

• Hue
• Visual experience specified by color names and
  related to the wavelength of light.
• Brightness
• Visual experience related to the amount of light
  emitted from or reflected by an object.
• Saturation
• Visual experience related to the complexity of
  light waves.

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Trichromatic theory

• Young (1802) and von Helmholtz (1852) both
  proposed that the eye detects 3 primary colors.
• Red, blue, and green
• All other colors derived by combination.

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Ambiguous Figure

• Also known as ambiguous illusions are pictures or
  objects that elicit a perceptual 'switch' between
  the alternative interpretations.
• The brain can interpret the ambiguous cues in two
  different ways.

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Distorting Illusions

• Characterized by distortions of size, length, or
  curvature.

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Visual constancies

• The accurate perception of objects as stable or
  unchanged despite changes in the sensory patterns
  they produce

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Color in context

• The way you perceive a color depends on the color
  surrounds.

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What we Hear

• Loudness
• The dimension of auditory experience related to
  the intensity of a pressure wave.
• Pitch
• The dimension of auditory experience related to
  the frequency of a pressure wave.
• Timbre
• The dimension of auditory experience related to
  the complexity of a pressure wave.

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What we Taste

• Five basic tastes
• Salty, sour, bitter, sweet, and umami
• Umami is one of the five basic tastes sensed by
  specialized receptor cells present on the human
• Umami is a Japanese word meaning savory, a
  "deliciousness" factor deriving specifically from
  detection of the natural amino acid, glutamic
  acid, or glutamates common in meats, cheese,
  broth, and other protein-heavy foods.
• Glutamate appears in foods and food ingredients
  such as
• soy sauce
• fish sauce
• parmesan
• anchovies
• monosodium glutamate (MSG)

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Different people have different tastes based on

• Genetics
• Culture
• Learning
• Food attractiveness

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What we Smell

• Airborne chemical molecules enter the nose and
  circulate through the nasal cavity.
• Vapors can also enter through the mouth and pass
  into nasal cavity.
• Receptors on the roof of the nasal cavity detect
  these molecules.

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Somatosensory System

• Widespread and diverse sensory system
• touch
• temperature
• pain
• kinesthesia (body position and movement)
• equilibrioception (balance)