SENSATION

CHARACTERISTICS OF SENSES

TRANSDUCTION

• The process in which a sense organ changes physical energy into electrical signals

• These signals become neural impulses which are sent to the brain for processing

ADAPTATION

• The decreasing response of the sense organs, the more they are exposed to a continuous level of stimulationSENSATIONS VS PERCEPTIONS

• Sensations are meaningless bits of information that result when the brain processes electrical signal coming from sense organs

• Perceptions are meaningful sensory experiences resulting from the combination of sensations

THE EYEThe eye is stimulated by Light wavesThe visibility of these light waves

depends in its length in the Electromagnetic Spectrum

• SHORT WAVELENGTHS: INVISIBLE

• JUST RIGHT WAVELENGTHS: VISIBLE

• LONG WAVELENGTHS: INVISIBLE

No, not this eye.

Structure and Function

Step 1: Light is scattered around.Step 2:Eye gathers this broad light to make a narrow, focused beam.Step 3: narrow beam passes through the CorneaStep 4: The Pupil allows light to enter the eyes.Step 5: the Iris regulates the amount of light that enters the eye.

Step 6: the light goes to the Lens which bends and narrows the light waves more

Step 7:After the light waves reach the RETINA, the transduction begins.

>1st Layer: The Back Layer

• photoreceptors

• Rods- Rhodopsin. dim light, black, white and shades of gray

• Cones- Opsin, bright light, colors and fine details

The chemicals in the rods and cones break down after absorbing the light waves.

>2nd Layer: The Middle Layer

• Ganglion cells -chemical breakdown from the rods and

cones generate tiny electrical force that if large enough, triggers nerve impulses in the neighboring ganglion cells

>3rd Layer: The Front LayerContains the optic nerve fibers that

brings the nerve impulses to the brain.

Visual Pathways

Step 1: The nerve impulses are carried by the Optic Nerve to the Thalamus where initial processing occurs. The thalamus relays it to the Occipital Lobe Step 2: At the back of the lobes lie the Primary Visual Cortex which transforms nerve impulses to simple visual sensations (Texture, lines, colors).Step 3: the Visual Association Areas assembles all of the basic sensations like the texture, lines and colors to create the whole image.

Color VisionTwo Theories:• TRICHROMATIC THEORY- there are 3 cones in the retina

containing Opsin. These opsins are responsive to different wavelengths that corresponds to the primary colors red, blue and green.

• OPPONENT PROCESS THEORY-ganglion cells in the retina and cells in

the thalamus respond to two pairs of colors; red-green and blue-yellow. One color is for excitement and the other is for inhibition.

THE EARAWESOME TERMS

• Sound waves - stimuli for hearing• Loudness - your subjective

experience of a sound's intensity- calculated through amplitude

• Pitch - your subjective experience of

a sound being high or low

- calculated through the frequency of sound waves

• Decibel - unit to measure loudness- our threshold for hearing

ranges from 0 dB (no sound) to

140 dB (can produce pain and

permanent hearing loss)

THE EAR

• Outer Earo External Ear - an oval-shaped structure that sticks out from the side of the head- picks up sound waves and sends them to the auditory canalo Auditory Canal- long tube that funnels sound waves down so that the waves strike a thin, taut membrane--the eardrum

o Tympanic Membrane- taut, thin structure commonly called the eardrum- vibrates when sound waves strike- passes the vibrations to the first small bone attached to it

• Middle Ear- a bony cavity that is sealed at each ends by membranes- the three tiny bones are collectively called ossicles, and because of their shapes, they are referred to as the hammer, anvil and stirrup- the ossicles act like levers that greatly amplify the vibrations and cause the oval window to vibrate as well

• Inner Ear - contains the cochlea and the vestibular system

Cochlea - bony coiled exterior shaped like a snail's shell (like a straw wound up)

Oval Window- vibrates the fluid in the cochlea's

tubes where the auditory receptors are located Auditory Receptors (hair cells)

- the mechanical bending of the hair cells generates miniature electrical forces that, if large enough, trigger nerve impulses Auditory Nerve

- carry nerve impulses to the brain

VESTIBULAR SYSTEM

The vestibular system is part of the inner ear, located above the cochlea. It includes three semicircular canals that contains fluids that react to the movements of the head. In the canals are the sensory hair cells that responds to the movements of the fluid.

>What causes motion sickness?Motion sickness is thought to develop when there is a sensory mismatch between the information of the vestibular system and the movement of your head.>What causes Meniere’s disease and vertigo?Both are caused by the malfunction of the semicircular canals of the vestibular system. Meniere’s Disease has symptoms like dizziness, nausea, vomiting, spinning and head splitting buzzing sounds. Vertigo, meanwhile, has symptoms like dizziness and nausea. Both don’t have cures.

TASTE• called a chemical sense because

stimuli are various chemicals

THE TONGUE

• the tongue has four basic tastes areas: sweet, salty, sour and bitter

• surface has small narrow trenches where the chemicals (the stimuli) go

• taste buds in the trenches produce nerve impulses that are sent to the brain which are transformed into sensations of taste

How can we tell the difference between two kinds of sweet?

FLAVOR

• combined sensation of taste and smell

SMELL (Olfaction)• chemical sense because its stimuli are

various chemicals that are carried by air

How do we smell?1.Stimulus (ex. skunk spray, eww) reach

the olfactory cells in the nose (receptors for smell)

2.Skunk spray molecules dissolve in the mucus (thick gluey film covering the olfactory cells) and trigger nerve impulses

1.g2.d3.Nerve impulses travel to the olfactory

bulb above the olfactory cells.4. Impulses are relayed to the primary

olfactory cortex where they are transformed into the olfactory sensations of a skunk spray.

Functions of Olfaction• Intensifies the taste in foods

• Warns us of potentially dangerous foods

• Smell elicits strong memories associated with emotional feelings

TOUCHThe sense of touch includes

pressure, temperature and pain.

Beneath the outer layer of the skin are half-dozen miniature sensors that are receptors for the sense of touch. These receptors changes mechanical pressure of changes in temperature into nerve impulses to be sent to the brain.

Receptors in the Skin• The skin has the outer layer that

contains no receptors. Underneath that thin layer has the first receptors that are threadlike extensions in form .The middle and fatty layer has receptors varying in shapes and functions.

• Free nerve endings are wrapped around the base of each hair follicle called hair receptors. They respond to the movement of our hair.

• The free nerve endings transmit the responses of the hair follicles as pressure and pain.

• The receptor called Pacinian Corpsucle is found in the fatty layers of the skin. It looks like an onion bulb and is highly sensitive to touch. It responds to vibrations.

Brain AreasAll these receptors in the skin send

their signals to the brain through the spinal cord then to the somatosensory cortex in the parietal lobe of the brain. The cortex transforms the impulses into basic sensations of touch, pressure, pain and temperature.

PAIN• Unpleasant sensory and emotional

experience that may result from tissue damage, one’s thoughts or beliefs, or environmental stressors

• Essential for survival

• Could be acute or chronic

• It was usually thought of as resulting only from tissue damage

• Involves social, psychological and emotional factors

picturesssss

GATE CONTROL THEORY OF PAIN

• Nonpainful nerve impulses (shifting attention) compete with pain impulses (ex. Headache) in trying to reach the brain

• This competition creates a bottleneck, or neural gate, that limits the number of impulses that can be transmitted

• You may not notice pain from a headache while thoroughly involved in some other activity

GATE CLOSED

No Pain, YAY!

Pain Signals

Nerve Impulses

Besides the effects of psychological factors, our initial perception of pain from a serious injury can be reduced by our brain’s own endorphins.

ENDORPHINS

• Chemicals produced by the brain and secreted in response to injury or severe physical or psychological stress

• Similar to morphine

• Produced in situations that evoke great fear, anxiety, stress or bodily injury

PERCEPTION

Becoming Aware of a Stimulus

THRESHOLD

• A dividing line between what has detectable energy and what does not

• Determines when we first become aware of a stimulus

• Absolute threshold – 50% chance of detecting stimulus

• Subliminal stimulus – 0-49%

Absolute threshold

Subliminal stimulus

Increasing Intensity

Ernst Heinrich Weber"Why is the music still loud? -_-" he

wondered....and soon developed the concept of:

JUST NOTICEABLE DIFFERENCE

• the smallest increase or decrease in the intensity of a stimulus that a person is able to detect

2oz vs 3oz 40lbs vs 41lbs

WEBER'S LAW• At lower intensities, small changes

between two stimuli can be detected as just noticeable differences; however, at higher intensities, only larger changes between two stimuli can be detected as JNDs

SENSATION VS PERCEPTIONBasic Difference

• Sensation- Our first awareness of some outside stimuli-meaningless bits of information

• Perception-Experience we have after the brain assembles the meaningless bits of information.

SENSATIONS TO PERCEPTIONS

1. Stimulus - any change in the environment and surrounding.

2. Transduction - the change of physical or chemical energy to electrical signals.

3. Brain: Primary Areas - these transforms impulses to basic sensations.

4. Brain: Association Areas - these assemble all the bits of sensory information from the Primary Areas to make meaningful images, sounds, smell, taste or feel.

5. Personalized Perceptions - varies on every person. It does not mirror reality but rather include our biases, emotions and memories to reflect reality.

RULES OF ORGANIZATION

• began with the Structuralists vs. Gestalt Psychologists debate

• specify how our brains combine and organize individual pieces or elements into a meaningful perception

FIGURE-GROUND

• we tend to automatically distinguish between a figure and a ground: the figure (more detail) stands out against the background

SIMILARITY

• we group together the elements that appear similar

CLOSURE

• we tend to fill in any missing parts of a figure and see the figure as complete

PROXIMITY

• we group together objects that are physically close to one another

SIMPLICITY

• stimuli are organized in the simplest way possible.

CONTINUITY

• we tend to favor smooth or continuous paths when interpreting a series of points or lines

PERCEPTUAL CONSTANCY

a. Size Constancy - the tendency to perceive objects as remaining the same size even when their images on the retina are constantly growing or shrinking

b. Shape Constancy - the tendency to perceive objects as remaining the same shape even when their images on the retina are constantly changing.

c. Brightness and Color ConstancyIt is the tendency to perceive brightness and color as still the same even though there were changes in lighting.

DEPTH PERCEPTION

• the ability of your eye and brain to add a third dimension, depth, to all visual perceptions

• the cues for depth perception are divided into two major classes: binocular (depends on the movement of both eyes) and monocular (produced by signals from one eye, and arise from the way objects are arranged)

Binocular Depth CuesCONVERGENCE

• based on signals sent from muscles that turn the eyes

• to focus on near or approaching objects, these muscles turn the eyes inward, toward the nose

• the brain uses the signals sent by these muscles to determine distance of the object

RETINAL DISPARITY

• depends on the distance between the eyes

• because of their different positions, each eye receives a slightly different image

• the distance between the right and left eyes' images is the retinal disparity

Monocular Depth CuesLINEAR PERSPECTIVE

• results as parallel lines come together, or converge, in the distance

RELATIVE SIZE

• results when we expect two objects to be the same size and they are not

• the larger will appear closer than the smaller

INTERPOSITION

• comes into play when objects overlap

• the overlapping object appears closer than the object that is overlappedTEXTURE GRADIENT

• areas with sharp, detailed texture are interpreted as being closer than those with less sharpness and poorer in detail

ATMOSPHERIC PERSPECTIVE

• created by the presence of dust, fog or clouds

• we perceive clearer objects as being nearer than the hazy or cloudy ones

MOTION PARALLAX

• based on the speed of moving objects

• the larger will appear closer than the smaller

ILLUSIONSStrange Perceptions

Two Reasons why Our Perceptions are not exact copies of Reality

1. Damage to Sensory Areas2. Our perceptions are influenced by our experiences

BUT... there's another reason:ILLUSIONS!

Illusion is a perceptual experience in which you perceive an image as being so strangely distorted that, in reality, it cannot and does not exist. It is created by manipulating perceptual cues so that your brain can no longer interpret space, size, and depth cues.

Impossible Figure - a perceptual experience in which the drawing seems to defy basic geometric laws.

Examples:Moon Illusion - the moon appears to be huge when it is near the horizon but appears really small when it's high in the sky.

Explanation: This illusion boggled researches and there were different explanations. The most recent one, however, is that the brain estimates how far away an object is and then interprets its size. The farther, the larger.

Ames Room -named after its designer, Albert Ames. This Illusion shows that perception can be distorted by changing depth cues.

Ponzo Illusion

Muller-Lyer Illusion

Learning from IllusionsIllusions teach us that when our

proven perceptual cues that we greatly rely change and manipulated, we can be deceived.Illusions also teach us that perception is a very active process, in which we continually rely on.