Sensation and Perception
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Sensation and Perception. Sensation A process by which our sensory receptors and nervous system receive and represent stimulus energy. Senses are the physiological methods of perception

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Sensation and Perception

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Sensation and perception

Sensation and Perception

  • Sensation A process by which our sensory receptors and nervous system receive and represent stimulus energy. Senses are the physiological methods of perception

  • Perception A process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Basic principles in sensation

Basic Principles in Sensation

  • Psychophysics Study of the relationship between physical characteristics of stimuli and our psychological experience of them

  • TransductionPhysical energy  neural impulses

Concepts in sensation

Concepts in Sensation

  • Absolute Threshold

  • Difference Threshold = Just Noticeable Difference (JND)

  • Weber’s Law orConstant

  • Signal Detection Theory (v. Threshold theory)

Sensation thresholds



of correct












Intensity of stimulus

Sensation Thresholds

  • Subliminal

Sensory adaptation

Sensory Adaptation

  • Sensory adaptation

Stabilized images on the retina

Stabilized Images on the Retina

Visual light adaptation

Visual Light Adaptation

  • Dark adaptation(20+ minutes) Increased sensitivity of rods and cones in darkness

  • Light adaptation(2-3 minutes) Decreased sensitivity

  • Afterimage effects Sense experience that occurs after a visual stimulus has been removed



  • PhototransductionThe conversion of one form of light energy to into neural impulses

    Light Characteristics

    • Wavelength (hue/color)

    • Intensity (brightness/amplitude)

    • Saturation (purity)

Sensation and perception

The spectrum of electromagnetic energy



  • Pupil Adjustable opening in the center of the eye

  • CorneaTransparent tissue where light enters the eye

  • Iris 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 (visual accommodation)



  • Accommodation (Visual) The process in 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. Contains rods and cones plus layers of neurons that process visual information. Key structure in phototransduction



Retinal reaction to light receptor cells

Retinal Reaction to Light (Receptor Cells)

  • Rods

    • Confined to theperipheral retina (120 million)

    • Detect black/white

    • Twilight or low light

  • Cones

    • Foundnear center of retina (8 million)

    • Fine detail and color vision

    • Well-lit conditions

    • Found mostly in fovea

Retinal reaction to light

Retinal Reaction to Light

  • FoveaCentral point in the retina, around which the eye’s cones cluster

  • Optic nerveNerve that carries neural impulses from the eye to the brain

  • Blind SpotPoint at which the optic nerve leaves the eye; no receptor cells

From eye to brain

From Eye to Brain

  • Optic nerve

    • Made up of axons of ganglion cells

    • carries neural messages from each eye to brain

  • Optic chiasm

    • Point where part of each optic nerve crosses to the other side of the brain

Visual information processing

Visual Information Processing

  • Feature Detector Cells Nerve cells in the brain that respond to specific features

    • Shape

    • Angle

    • Movement (direction specific, MAE due to adaptation!)

Visual information processing1

Visual Information Processing

  • Parallel Processing

    • Simultaneous processing of several aspects of a problem simultaneously

Color vision in other species

Color Vision in other Species

  • Other species see colors differently than humans

    • Most other mammals are dichromats

    • Rodents tend to be monochromats, as are owls who have only rods

    • Bees can see ultraviolet light

Theories of color vision

Theories of Color Vision

  • Trichromatic theory (Young-Helmholtz)Holds that the retina contains three types of color receptors (cones) sensitive to red, blue and green.

    • Experience of color is the result of mixing of the signals from these receptors (additive process)

    • Accounts for some types of colorblindness

  • It cannot explain all aspects of color vision

    • People with normal vision cannot see “reddish-green” or “yellowish-blue”

    • Color afterimages

Theories of color vision1

Theories of Color Vision

  • Additive color mixing

    • Mixing of lights of different hues

    • Lights, T.V., computer monitors (RGB)

  • Subtractive color mixing

    • Mixing pigments, e.g., paints

Colorblindness color deficient vision

Colorblindness (Color-deficient vision)

  • Approximately 10% of men and 1% of women have some form of colorblindness

  • Dichromats

    • People who are blind to either red-green or blue-yellow

  • Monochromats

    • People who see no color at all, only shades of light and dark. Very rare

Opponent process theory

Opponent Process Theory

  • Opponent-process theoryProposes that opposing retinal processes (color pairs) enable color vision

    • Three pairs of color receptors (On-Off)

      • Yellow-blue

      • Red-green

      • Black-white

    • Explains color afterimages

    • Both theories are valid

Afterimage effect

Afterimage Effect

Afterimage effect1

Afterimage Effect

Bizarre visual phenomena

Bizarre visual phenomena

  • Blindsight (damage to cortex, not eye)

  • Prosopagnosia

  • Various types of agnosia

Concepts in audition hearing

Concepts in Audition (Hearing)

  • Acoustical transductionConversion of sound waves into neural impulses in the hair cells of the inner ear

  • Characteristics of Sound

    • Frequency (pitch)

    • Intensity (loudness)

    • Quality (timbre)

The intensity of common sounds

The Intensity of Common Sounds

The ear

The Ear

  • Middle Ear

    • Chamber between eardrum (tympanic membrane) and cochlea containing three tiny bones(ossicles - hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

  • Inner Ear

    • Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs

  • Cochlea

    • Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals.

The inner ear

The Inner Ear

  • Basilar membrane

    • Membrane in the cochlea which contains receptor cells, called hair cells

  • Auditory nerve

    • Connection from ear to brain

    • Provides information to both sides of brain

Theories of audition

Theories of Audition

  • Place Theory suggests that sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch (explains high pitch)

  • Frequency Theory states that the rate of nerve impulses matches the frequency of a tone, thus enabling us to sense its pitch (low pitch)

  • Volley PrincipleThe pattern of sequential firing that supports frequency theory

Binaurality and sound localization

Binaurality and Sound Localization

Hearing loss

Hearing Loss

About 30 million people have some form of hearing damage in the U.S. Can be caused by injury, infections, explosions, long-term exposure to loud noises (ipods!)

  • Conduction Hearing Loss

    • Caused by damage to the mechanical system that conducts sound waves to the cochlea

  • Sensorineural Hearing Loss

    • Caused by damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness

The skin senses

The Skin Senses

  • Skin Sensations

    • pressure

      • only skin sensation with identifiable receptors

    • warmth

    • cold

    • pain

The skin senses touch sense aka haptic sense

The Skin Senses (Touch Sense akaHaptic Sense)

  • Skin is the largest sense organ

  • Pressure, temperature, vibration and pain systems

  • Pain tells the body that something has gone wrong

  • Analgia

Sensation and perception


  • Gate-Control TheoryStates that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain (Melzik and Wall)

    • “Gate” opened by the activity of pain signals traveling up small nerve fibers

    • “Gate” closed by activity in larger fibers or by information coming from the brain

Biopsychosocial influences and pain

Biopsychosocial Influences and Pain



Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes (taste buds). Receptors for a fifth taste have been named called “Umami”








Receptor cellsare located in taste buds

Taste buds are located in papillae on the tongue

Chemicals dissolve in saliva and activate receptors

Sensation and perception

Sensory Interaction

When one sense affects another sense, sensory interaction takes place.

This is especially apparent with the interaction between smell and taste

The taste of a banana interacts with its smell and its texture on the tongue to produce flavor.

  • Cross-adaptation (smell/taste)

Olfactory sense

Olfactory Sense

  • Detecting common odors

    • Odorant binding protein is released and attached to incoming molecules

    • These molecules then activate receptors in the olfactory epithelium

    • Axons from those receptors project directly to the olfactory bulb

Olfactory sense1

Olfactory Sense

  • Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 10+ million receptors to sense smell. Unlike taste, there are many different forms of smell

  • Only sense to bypass thalamus and have specific brain structure

Smell and memory

Smell and Memory

  • The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell


Pheromones and vomeronasal organ vno

Pheromones and Vomeronasal Organ (VNO)

  • Pheromones

    • Used by animals as a form of communication

    • Provides information about sexual receptivity

  • Pheromones stimulate the vomeronasal organ (VNO)

  • Human responsiveness?

Body position and movement

Body Position and Movement

  • Kinesthetic senseprovides information about the speed and direction of movement

    • Stretch receptors sense muscle stretch and contraction

    • Golgi tendon organs sense movement

  • Vestibular sense provides information about equilibrium and body position

    • Fluid moves in two vestibular sacs

    • Vestibular organs are also responsible for motion sickness which may be caused by discrepancies between visual information and vestibular sensation

Sensation phenomenon

Sensation Phenomenon

  • Non-human senses – magnetoception, electroreception, pressure and current reception (lateral line), polarization

  • Hypersensors (humans)– echolocation, tetrochromats, supertasters (or hypo…)

  • Synaesthesia



  • How common is synesthesia?

  • To what extent are synesthetes

    • More vulnerable to mental illness?

    • More inclined to the arts? The connection?

    • More apt to be one gender or another?

    • Genetically influenced?

  • What synesthetic phenomenon is most commonly reported? TWE is it idiosyncratic?

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