Sensation Approximate Absolute Thresholds Subliminal Perception

Main Senses Perception

True or False?T/F People have five senses.

T/F If we could see waves of light with slightly longer wavelengths, warm-blooded animals would glow in the dark.

T/F People sometimes hear what they want to hear.

T/F Some people can read other people’s minds.

The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural impulses.

Phi Phenomenon

Sensation and Perception Defined

Sensation: The detection of physical energy emitted or reflected

by physical objects. Sense Receptors:

Specialized cells that convert physical energy in the environment to chemical and electrical energy in the body.

Perception: The process by which the brain organizes and

interprets sensory information.

Transduction: Transformation of stimulus information into

nerve impulses (electrical).

SensationAbsolute Threshold: Smallest quantity of physical energy that

can be reliably detected by an observer.

Difference Threshold: (Just Noticeable Difference) Smallest difference between two stimuli that can be reliably

detected by an observer.

Weber’s Law: Thresholds increase in proportion to the background. When you are in a noisy environment you must shout to be

heard while a whisper works in a quiet room.

SensationSignal Detection Theory: Divides a sensory signal into two processes:

Sensory process Decision process

After receiving a weak stimulus you will: Hit: Detect a signal that was there. False Alarm: Says the signal was there when it was not. Miss: Fail to detect a signal when it was present. Correct Rejection: Correctly say the signal was absent when it

was not there.

Approximate Absolute Thresholds Vision:

Candle flame seen from 30 miles on a clear, dark night. Hearing:

Tick of a watch from 20 feet in very quiet conditions. Smell:

Drop of perfume diffused throughout a three-room apartment.

Taste: .0356 ounce of table salt in 529 quarts of water.

Touch: Bee wing falling on your cheek from a height of 1

centimeter.

Sensation

Sensory Adaptation: Reduction or disappearance of sensory responsiveness that

occurs when stimulation is unchanging or repetitious. Brain responds more readily to new stimuli.

Sensory Deprivation: Absence of normal levels of sensory stimulation. Selective Attention protects us from sensory overload-

○ Not capable of fully processing all incoming sensory information.

○ We focus attention on selected aspects of the environment and block out others.

Subliminal Perception Definition: Below threshold.

We can process some information from stimuli too weak to recognize.

Effect of Subliminal Stimulation: A subtle, fleeting effect on thinking.

Does subliminal advertising work? No. The goal of using subliminal

advertising is to increase the likelihood that you will buy a particular product.

Main SensesMain Senses: (theoretical)

1. Visual

2. Audition

3. Tactile (touch)

4. Gustation (taste)

5. Olfactory

6. Proprioception (kinesthetic in parietal)

7. Immunological

VisionWhy are we so dependent on our visual sense? Would we be

as advanced as we are today without it?

Fun Facts: More information comes from our eyes than any other

senses. Our eyes see through visible light.

Our eyes pick up these light waves. Color itself is not a property of the external world.

It is derived from the wavelength of visible light.

Colorblindness Prevalence: One out of twelve men and one out of two hundred

women. Protanomaly (one out of 100 males): Red-weakness,

Deuteranomaly (five out of 100 males): Green-weakness, Dichromasy

Monochromats: People who are totally colorblind. Dichromats: People who are blind to either red-green or

yellow-blue.

Colorblindness

Vision Humans:

Lack certain pigments found in primate eyes. (our sclera is white)

Contrast in color between our facial skin, sclera and irises.

Gorillas: Low contrast between their

eyes and facial skin.

Afterimages : Sensations that linger after the stimulus is removed.Fix your eyes on the dot in the center of the flag.

Trichromatic Theory There are three types of cones: red, green, and blue. The colors we see are the result of a combination of the differing

amount of light absorbed by the three types of cones.

Rods: Dim light. (better with edges and curves) Concentrated in the periphery.

Cones: Color vision. (very poor at night) Concentrated in the fovea.

Ganglion cells: Neurons in the retina of the eye. Gather information from receptor cells.

Path from Eye to Visual Cortex

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photo-photo-receptorsreceptors

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LGNLGNvisual visual cortexcortex

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Vision Cornea

Transparent front part of the eye that covers the iris, pupil, and anterior chamber.

Refracts light and aids in focusing.

Optic Nerve Transports sensory material to optic chiasm.

Iris Provides color to the eye.

Fovea Responsible for sharp central vision. Necessary for reading, TV, driving. Any activity where visual detail is important.

Pupil Black circular/slit opening in the center of the iris. Regulates the amount of light that enters the eye.

Retina Back of eye. Contains receptors.

Gestalt Principles of PerceptionPrinciples that describe the brain’s organization of sensory information

into meaningful units and patterns.

Proximity: Things near each other are grouped together.

Closure: The brain will fill in gaps in order to make a whole.

Similarity: Things that are alike are perceived as belonging together.

Continuity: Lines and patterns are perceived as continuing in

time and space.

Gestalt Principles of Perception

Perceptual Set: Readiness to detect a particular stimulus in a given context.

Gestalt Principles of Perception Law of Pragnanz Figure-Ground Organization Isomorphism Laws of Perceptual Grouping

Gestalt Principles of Perception

The Herman Grid

Figure-Ground Distinction Figure: Entity perceived to stand apart from the

background. Ground: Background against which a figure

appears.

Perceptual Constancies Size constancy

The perception of an object as the same size

regardless of the distance from which it is viewed.

Shape constancy Tendency to see an object as the same shape

no matter what angle it is viewed from.

Brightness constancy We perceive an object as having a constant lightness

even while its illumination varies.

Color constancy An inclination to perceive familiar objects as retaining

their color despite changes in sensory information.

Perceptual CuesSuperposition Monocular distance cue in which one object,

by partially blocking another, is perceived as being closer.

Linear Perspective: Two parallel lines appear to converge at the horizon.

Elevation: The higher on the horizontal plane an object is, the farther away it appears.

Depth Perception (seeing in 3D)

Monocular cues: Depth cues requiring only one eye. Binocular cues: Depth cues requiring both eyes.

HearingFun Facts: Sense of hearing never turns off at one time or another. Cerebellum

Uses the fluid in the cochlea ( part of the semicircular canals) to aid in balance.

Organ of Corti (pronounced: cortee): Structure in the cochlea containing hair cells that serve as the receptors for

hearing. Sensory receptors called hair cells

turn air pressure changes into neural signals.

Major Divisions: External, Middle, Inner

Decibel Level for Common Sounds

Auditory Pathway

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cochleacochlearr

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Hearing

If a tree falls in a forest and no one is around to hear it, does it make a sound?

TactileFun Facts: We have more pain nerve endings than any other type. The least sensitive part of your body is the middle of your back. The most sensitive areas of your body are your-

Hands, Lips, Face, Neck, Tongue, Fingertips, Feet Shivering is a way your body has to get warm. There are approximately 100 touch receptors in your fingertips.

TasteFun facts: Your sense of taste can replace itself. Single taste bud contains 50-100 taste cells Each taste cell can represent all 5 taste sensations. Taste buds are the structures on the tongue that contain taste receptor cells. An adult has about 10,000 taste buds. Taste receptors die and are replaced every 7 days. The number of taste buds decrease with age.

Taste: The ability to respond to dissolved molecules and ions called tastants. Detect taste with taste receptors clustered in taste buds.

TasteFive primary taste sensations:

I. Salty-helps an animal suffering from Na+ deficiency.

II. Sour-detects acids in food.

III. Sweet-detects glucose in food.

IV. Bitter-typically defective or rotten compounds.

V. Umami-glutamic acid salts such as MSG.

Anatomical Pathway

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primary primary somatosensorsomatosensor

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anterior-anterior-insular insular cortexcortex

Olfaction Olfaction: Sense of smell

Olfactory bulbs: Brain sites of olfactory processing

Pheromones: Chemical signals released by organisms to

communicate with other members of the species.

Detecting Odors: Odorant binding protein (OBP) makes the detection of odors possible. A nasal gland coats airborne molecules with OBP to facilitate detection by

the receptors in the olfactory epithelium.

Variations in Odor Sensitivity Women have a better sense of smell than men. The ability to smell diminishes with age. Smell acuity is greatest during early adulthood (ages 20-40).

Pheromones Pheromones are chemicals produced by an animal that affects the

behavior of another animal through scent. Receptors in the vomeronasal organ detect pheromones.

ProprioceptionDefined:

The movement of arms and legs in relation to each other.

Kinesthetic Sense: Provides specific information about muscle movement, changes in posture,

and strain on muscles and joints. Receptors: stretch receptors and Golgi tendon organs (provide information

about stretching and contraction of individual muscles).

Vestibular Sense o The sense of equilibrium and awareness of body position in space.o 2 types of vestibular senses:

— body rotation

— gravitation and movement

ImmunologicalImmune System: Process in an organism that identifies and removes antigens

by identifying items that are non-self.