Module 3: Sensation & Perception

Sensation

• Is stimulation of sensory receptors and transmission of sensory information to the central nervous system

Perception

• Is process by which sensations are organized and interpreted to form an inner representation of the world

Absolute Threshold

• weakest amount of a stimulus that can be distinguished from no stimulus at all.

• Detected 50% of the time

• Vision

• Hearing

• Taste

• Smell

• Touch

• What are the absolute threshold (5)

Vision

Absolute Threshold

• a candle flame viewed from about 48km on a clear night

Hearing

Absolute Threshold

• a watch ticking from about 20 feet away in a quiet room

Taste

Absolute Threshold

• 1 teaspoon of sugar dissolved in 7.5L of water

Smell

Absolute Threshold

• about one drop of perfume diffused though a small house

Touch

Absolute Threshold

• the pressure of the wing of a fly falling on a check about a distance of about 0.4 inch

Subliminal stimulation

Absolute Threshold

• Sensory stimulation that is below a person’s absolute threshold for conscious perception

• Visual stimuli flashed too briefly to be processed

• Auditory stimuli played a volume to low to consciously hear or played backward

Difference threshold

• Minimum difference in magnitude of two stimuli required to tell them apart

• Detected 50% of the time

• Weber’s Constant: Standard of difference of 2%

• Just Noticeable Difference (JND): Minimum difference a person can detect

Weber’s Constant

Difference Threshold

• Standard of difference of 2%

Just Noticeable Difference

Difference Threshold

• Minimum difference a person can detect

Signal-Detection Theory

• Stimulus characteristics and psychological factors interact to influence whether a stimulus is detected

• Psychological factors: Learning, motivation, psychological states, (Fatigue, alertness)

• Sensitization

• Desensitization

Sensory Adaptation (2)

Sensitization

Sensory Adaptation

• Positive Adaptation: Process by which we become more sensitive to stimuli of low magnitude

Desensitization

Sensory Adaptation

• Negative Adaptation: Process by which we become less sensitive to stimuli that remains the same

Visible Light Spectrum

• Is the section of the electromagnetic radiation spectrum that is visible to the human eye

• Wavelength (Nanometers)

Eye

Light enters through a narrow opening

• Cornea

• Iris

• Pupil

Cornea

Eye

• Transparent eye cover

Iris

Eye

• Muscle; colored part of the eye

Pupil

Eye

• Opening in the iris

• Sensitive to light and emotion

Lens

Eye

• Changes in thickness for focusing

• Image is projected onto retina

Light sensitive surface

Eye

• Retina

• Photoreceptors

• Rods, Cones, Bipolar, and ganglion cells

Optic Nerve

Eye

• Axons of Ganglion neurons form optic nerve

• Conducts sensory input to brain (Occipital Lobe)

Cones

Eye

• Most densely packed in center of retina (Fovea)

• Provide color vision

Rods

Eye

• Provide vision in black and white

• More sensitive to dim light than cones

Visual Acuity

• Greatest in the fovea

• Blind spot: point in retina where ganglion cells converge

• Nearsightedness

• Farsightedness

• Presbyopia

• Trichromatic Theory

• Opponent-Process Theory

Theories of Color (2)

Trichromatic Theory

Theories of Color

• Three types of cones

• Respond to red, green, or blue

Opponent-process Theory

Theories of Color

• Three types of color receptors

• respond to red or green, blue or yellow, or light or dark

• Cannot respond to both at simultaneously

• Trichromat

• Monochromat

• Dichromat

Color Blindness (3)

Trichromat

Color Blindness

• Normal color vision

Monochromat

Color Blindness

• totally color blind

Dichromat

Color Blindness

• Partial color blindness

• Discriminate between two colors

• More common in males (Sex linked trait)

Visual Perception

• Process used to organize sensory impressions caused by the light that strikes our eyes

• Sensation is a mechanical process

• Perception is an active process: Involves knowledge, expectations, and motivation

Perceptual Organization

• Figure: Ground perception

• Ambiguous, unstable figures

• Proximity

• Similarity

• Continuity

Gestalt Rules For Perceptual Organization (3)

Proximity

Gestalt Rules For Perceptual Organization

• Nearness of objects

Similarity

Gestalt Rules For Perceptual Organization

• Similarity of objects

Continuity

Gestalt Rules For Perceptual Organization

• Series of points having unity

Sound waves

• require a medium; air or water

• compress and expand molecules of the medium, creating vibrations

• a single cycle of compression and expansion is one wave of sound

• Human ear is sensitive to sound waves with frequencies of 20 to 20,000 cycles per sound

Pitch

• Frequency (# of cycles per second)

• Expressed in Hertz (Hz)

• Pitch of women’s voice is higher than men’s

Loudness

• Height (Amplitude) of sound waves

• Expressed in decibels (DB)

Ear

Shaped and structured to:

• Capture sound waves

• Vibrate in sympathy with them

• Transmit auditory information to the brain

• Outer ear

• Middle ear

• Inner ear

• Auditory nerve

Parts of the Ear (4)

Outer ear

Part of the Ear

• Funnels sound waves to the eardrum

Middle ear

Part of the Ear

• Eardrum, hammer, anvil and stirrup

• Acts as an amplifier

• Oval window - Round window

Inner ear

• Cochlea

• Basilar membrane

• Organ of Corti

Loudness and sequence

Locating Sounds

• ___________ in which sounds reach the ear provide cues

• May turn head to clarify information

Conductive deafness

• Damage to middle ear

• Hearing aids can help

Sensorineural Deafness

• Damage to inner ear or auditory nerve

• Conductive deafness

• Sensorineural deafness

Type of deafness (2)

Auditory nerve

• Cochlear implants may help with damage to inner ear, but not _____________

• Smell

• Taste

The chemical senses (2)

Olfactory membrane

Smell

• Odors trigger receptor neurons in ________

• Odors are sample molecules of substances in the air

Olfactory nerve

Smell

• Sensory information about odors is sent to the brain through the _________

• Odor contributes to flavor of foods

Receptor Neurons

• Taste is sensed through taste cells

• _________ on taste buds

• Sweet

• Sour

• Salty

• Bitter

Four Primary Taste Qualities

Umami

• Fifth basic taste - savory

• Odor

• Texture

• Temperature

• Taste

Flavor of food depends on: (4)

sensitivities

• Individuals have taste _________

fire

Touch and Pressure

• Skin sensory receptors _______ when skin surface is touched

• Active touching

Nerve endings

Touch and Pressure

• Some areas of the body are more sensitive

• ________ are more densely packed

• More sensory cortex is devoted to perception of sensations in those areas.

• increases

• decreases

Temperature

• Receptors are located just beneath the skin

• Skin temperature ________ - receptors for warmth fire

• Skin temperature ________ - receptors for cold fire

• Sensations for temperature are relative

• Nociceptors

• Pain

Pain

• ________ in skin are stimulated

• ________ is usually sharpest where nerve endings are densely packed

• Pain can be felt deep within the body

• No nerve endings for pain in the brain

Prostaglandins

• Facilitate transmission of pain message

• Heighten circulation to injured area (inflammation)

• Pain-relieving drugs inhibit production of prostaglandins

• Emotional response and response to stress affect degree of pain

Kinesthesis

• Sense that informs you about the position and motion of your body

• Sensory information is sent to the brain from sensory organs in joints, tendons, and muscles.

Vestibular sense

• Housed mainly in semicircular canals in your ears

• Monitor your body’s motion and position in relation to gravity

Extrasensory Perception - ESP

Perception through means other than sensory organs

• Precognition

• Psychokinesis

• Telepathy

• Clairvoyance

• Precognition

• Psychokinesis

• Telepathy

• Clairvoyance

What are the Extrasensory Perception - ESP

Precognition

Existence of ESP

• Foretelling of future events

Psychokinesis

Existence of ESP

• Ability to affect the physical world through thoughts

Telepathy

Existence of ESP

• Ability to send messages through the mind

Clairvoyance

Existence of ESP

• Ability to perceive events with no direct stimuli