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chapter 6. 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

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definitions

chapter 6

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

sensation
Sensation
  • What are the sensory systems?
      • Sight, sounds, touch, pain, smell, taste, sensation of movement
  • Why are the sensory systems important?
      • Perception of external world
      • Maintains arousal, forms body image, regulates movement
      • Basis for our knowledge about the world and our surroundings.
psychophysics
Psychophysics
  • Correlates quantitative aspects of physical stimuli (energy) with the sensations they evoke
  • 4 elementary attributes:
      • Modality
      • Intensity
      • Duration
      • Location
attributes of sensation modality
Attributes of Sensation:Modality
  • Quality of a sensation
      • Different forms of energy = Different sensations
      • 5 major: vision, hearing, touch, taste, smell
        • Submodalities:
          • Touch – sweet, salty, bitter, sour
          • Vision – color, movement
  • Law of Specific Energies
      • 1826 Johannes Muller
      • Each modality = activated by a specific stimulus = different sensory nerve fiber
  • Sensory receptors are maximally sensitive to a specific energy
attributes of sensation intensity
Attributes of Sensation:Intensity
  • Strength of Energy  Amount of sensation
      • Frequency of action potentials
        • strong stimulus = more action potentials fired
      • # of fibers activated
        • strong stimulus = more fiber stimulated
  • Absolute Threshold
      • Smallest amount of energy/stimulation that can reliably be detected
      • Variable
        • Influenced by practice, fatigue, context
absolute thresholds

chapter 6

Absolute thresholds

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

attributes of sensation intensity9
Attributes of Sensation:Intensity
  • Strength of Energy  Amount of sensation
      • Frequency of action potentials
        • strong stimulus = more action potentials fired
      • # of fibers activated
        • strong stimulus = more fiber stimulated
  • Absolute Threshold
      • Smallest amount of energy/stimulation that can reliably be detected
      • Variable
        • Influenced by practice, fatigue, context
  • Difference Threshold
      • Smallest difference that can be detected when 2 stimuli are compared
      • Just Noticeable Difference (JND)
signal detection theory

chapter 6

Signal-detection theory

A psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process and quantifies the ability to distinguish between the stimuli and noise

drugs mechanism of action on the sensation of pain
Drugs – Mechanism of Action on the sensation of pain
  • Drugs that elevate the pain threshold
    • Morphine
          • Reduces detectibility of painful stimuli = raises threshold
          • Elevates criterion used to determine if a stimuli is painful = creates noise
    • Marijuana
          • Elevates criterion used to determine if stimuli is painful = makes noise
attributes of sensation duration
Attributes of Sensation:Duration
  • Stimulus intensity and Perceived Intensity
  • 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
attributes of sensation location
Attributes of Sensation:Location
  • Spatial aspects of sensation:
        • Ability to locate origin of sensation
        • Ability to distinguish 2 closely spaced stimuli
  • Two-Point Threshold
        • Minimum distance between 2 stimuli that allows them to be perceived as distinct
  • Function of receptive field of receptor and sensory neurons
commonalities of the senses
Commonalities of the Senses
  • All extract same basic information
      • Modality, intensity, duration, location
  • Similar organization
      • Sensory receptors for specific type of energy
      • Receptor transforms energy into electrochemical signal  action potentials
      • Travel up afferent fibers to the brain
      • Relay information to Thalamus (except smell)
      • Continue on to specific regions in cortex
vision

chapter 6

Vision

Stimuli (energy) = light waves

3 Psychological Aspects of Vision:

Hue

Related to the wavelength of light

Brightness

Related to the amount of light emitted from or reflected by an object – amplitude of wavelength

Saturation

Related to the complexity of light waves - # of different wavelengths

vision16
Vision

Adapted from Univ. Virginia, Dept of Astronomy

anatomy of the eye

chapter 6

Anatomy of the Eye

Cornea

Protects eye and bends light toward lens

Lens

Focuses on objects by changing shape

Iris

Controls amount of light that gets into eye

Pupil

Aperture through which light reaches the retina

rods and cones

chapter 6

Rods and Cones

Retina

Neural tissue lining the back of the eyeball’s interior containing the receptors for vision

Rods

Visual receptors that respond to dim light

Cones

Visual receptors involved in color vision

your turn

chapter 6

Your turn

You have a hard time locating your red car at night, in the poorly lit mall parking lot. Why?

1. Your rods are less sensitive to color in dim light.

2. Your cones, which detect color, do not function well in dim light.

3. Your ganglion cells receive insufficient overall stimulation to

function.

4. Your rods, which detect color, do not function well in dim light.

the visual system is not a camera

chapter 6

The visual system is not a camera

Visual processing is done in the brain

The visual image that was reflected onto our retina is broken up into simple and complex features that the brain perceives, processes and interprets

Simple features - light and dark spots

- Ganglion cells and neurons in Thalamus

Complex features – Lines with specific orientations, bulls-eyes, spirals, faces)

- Feature-detector cells in the Visual cortex

- Sensitive to specific features in the environment

slide24

chapter 6

Visual Cortex Neurons:Feature-Detector CellsRespond to lines oriented in a particular direction and in a particular space in the visual field

Hubel & Wiesel Experiment

hubel and wiesel s experiment

chapter 6

Simple Cell in Visual Cortex

Hubel DH Sci Amer 209:54-62,1963

Hubel and Wiesel’s experiment
how do we see color
How do we see color?
  • Two theories:
    • Trichromatic theory
    • Opponent-process theory
trichromatic theory

chapter 6

Trichromatic theory

Young-Helmholtz Theory:

The eye detects 3 primary colors

Red, blue, and green

Retina has 3 basic cones detects the 3 primary colors

All other colors detected by the combined activity of these 3 cones

opponent process theory

chapter 6

Opponent-process theory

The visual system treats pairs of colors as opposing or antagonistic

  • 3 opponent channels
    • Red-Green
    • Blue-Yellow
    • Black-White

If opponent-process cells are inhibited by a color then removal of the color results in a burst of activity

  • Many respond in the opposite fashion to red and green, i.e. fire in response to red and turn off in response to green
  • Negative afterimage
form perception gestalt principles

chapter 6

Form Perception:Gestalt principles

Proximity

Things close to one another are grouped together

Closure

The brain tends to fill in gaps to perceive complete forms

form perception gestalt principles cont

chapter 6

Form Perception:Gestalt principles cont.

Similarity

Things that are alike are perceived together

Continuity

Seeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction.

your turn31

chapter 6

Your turn

Which Gestalt principle is illustrated by the fact that we see columns of dots rather than rows in this diagram?

1. Similarity

2. Proximity

3. Closure

4. Continuity

depth and distance perception

chapter 6

Depth and distance perception

Binocular cues

Require both eyes working together

Convergence

Turning inward of the eyes, which occurs when they focus on a nearby object

Retinal disparity

The slight difference in lateral separation between two objects as seen by the right and left eyes

depth and distance perception33

chapter 6

Depth and distance perception

Monocular cues

For objects over 50 feet away

Does not depend on both eyes

Interposition

Linear Perspective

Light and Shadow

Motion Parallax

Relative Size

Relative Clarity

Texture Gradients

visual constancies

chapter 6

Visual constancies

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

Shape constancy

Location constancy

Size constancy

Brightness constancy

Color constancy

last class in review
Last Class in Review
  • Sensation

The detection of physical energy emitted or reflected by physical objects

  • Perception

The process by which the brain organizes and interprets sensory information

  • Psychophysics – attributes of sensation

Modality, Intensity, Duration, Location

      • Law of Specific Energies
      • Absolute Threshold vs. Difference Threshold (JND)
      • Adaption and Deprivation
      • Two-Point Threshold
  • Vision
    • Psychological Attributes – hue, brightness, saturation
    • Anatomy – visual receptors = rods and cones; feature detector cells
    • Depth and Distance perceptions: monocular and binocular cues
    • Gestalt Principles: proximity, closure, similarity, continuity
sensation and perception36

chapter 6

Sensation and Perception
  • Learning Objectives:
  • What are the 3 main psychological dimensions of hearing?
  • What are the major structures of the inner ear that contribute to the sense of hearing?
  • Understand how the Gestalt principles may apply to other sensations, such as hearing.
  • What are the 5 major tastes? Why do people tastes things differently?
  • What are the basic senses of the skin? How is sensation organized? (hint: understand somatotopy)
  • How does gate-control theory account for our perception of pain?
  • Is there any evidence that some perceptual abilities are present from birth? What are these abilities and what is the evidence?
  • What 5 factors can influence our perception?
what we hear audition

chapter 6

What we hear (audition)

Stimulus (energy) = wave of pressure caused by vibrations

3 Psychological Aspects of Sound:

Pitch

Frequency of a pressure wave

Measured in hertz (Hz)

Loudness

Intensity (amplitude) of a pressure wave

Measured in decibels (dB)

Timbre

Complexity of a pressure wave

White noise – all frequencies of the sound spectrum

psychological aspects of sound

Example of differences in pitch and complexity

Psychological Aspects of Sound

From Genetic Science Learning Center, University of Utah, http://gslc.genetics.utah.edu.

gestalt principles in audition
Gestalt Principles in Audition
  • Proximity
        • Which sounds go together to form words
  • Continuity
        • Helps you follow 1 persons voice in a room full of background noise
  • Similarity
        • Might also help you follow 1 persons voice in a room full of background noise
  • Closure
        • Helps you complete words when the speakers voice trails off
auditory localization

chapter 6

Auditory localization

Sounds from different directions are not identical as they arrive at left and right ears.

Loudness

Timing

Phase

The brain calculates a sound’s location by using these differences.

taste gustation

chapter 6

Taste (Gustation)

Taste buds =

Bundles of taste receptor cells

Taste hairs (microvilli) contain taste receptors

Taste stimuli (energy) = chemical

Taste receptor cells send signals to sensory nerves (taste nerves)

Sensory nerves send action potential to the brain

five tastes

chapter 6

Five tastes

Five basic tastes

Salty – keeps electrolytes (salt-balance) in check

Sour – detects acidity = rancid food

Bitter – allows sensing of natural poisons

Sweet – energy rich nutrients, presence of sugars

Umami – taste of amino acids (glutamate) = protein rich foods

Why do people have different tastes?

Genetics - supertasters

Culture

Learning

Food attractiveness

smell olfaction

chapter 6

Smell (Olfaction)

Smell stimuli (energy) = chemicals

Enter through the nose or mouth and pass into nasal cavity.

Receptors  Olfactory nerve  Olfactory bulb  Pyriform cortex, hypothalamus, thalamus, frontal cortex, hippocampus

senses of the skin
Senses of the Skin
  • Basic skin senses:
      • Tactition (touch) -
          • stimuli is pressure
          • mechanoreceptor
      • Thermoception (hot & cold)
          • stimuli is thermal
          • thermoreceptor
      • Nociception (pain)
          • stimuli is noxious
          • nociceptor
somatotopy
Somatotopy

Adapted from Sabes Lab - UCSF

the environment within

chapter 6

The environment within

Kinesthesis

The sense of body position and movement of body parts

Equilibrium

The sense of balance

- Semicircular canals

Sense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head

critical period

chapter 6

Zebra finches learn their adult song from a tutor during a critical period

Critical period

An important period of time during development when the brain is capable of acquiring a specific ability

  • Environmental stimulation needed to strengthen hard-wired innate connections
  • If infants miss out on experiences during a crucial period of time, perception will be impaired.
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