What Is Sensation? The process by which our sensory systems and nervous system receive stimuli from our environment.

What Is Perception? The process of organizing and interpreting sensory information into meaningful experiences.

Processing Bottom-up processing: Focuses on raw material entering through our senses Top-down: Focuses on how our expectations and experiences interpret incoming sensory information. Slide # 3

Slide # 4 What Is Meant by a Threshold? Threshold: an edge or boundary Absolute threshold: the minimum amount of a stimulation that a person can normally detect aka: just noticeable difference

Absolute Thresholds Vision: a flame from a single candle 30 miles away Hearing: ticking of a watch 20 feet away Taste: one teaspoon of sugar in two gallons of water Smell: one drop of perfume in a small house Touch: the wing of a bee brushing your cheek

Sensory Adaptation Senses are most responsive to increases and decreases rather than ongoing unchanging stimulation Our senses have the ability to adapt

The Stroop Effect A B

Vision: The Eye

Cornea The clear bulge on the front of the eyeball Begins to focus the light by bending it toward a central focal point Protects the eye

Iris A ring of muscle tissue that forms the colored portion of the eye; creates a hole in the center of the iris (pupil) Regulates the size of the pupil by changing its size--allowing more or less light to enter the eye

Pupil The opening in the eye that controls the amount of light entering the eye (surrounded by the iris) In bright conditions the iris expands, making the pupil smaller. In dark conditions the iris contracts, making the pupil larger.

Lens A transparent structure behind the pupil; focuses the image on the back of the eye (retina) Glasses or contacts correct problems in the lens’ ability to focus.

Retina Light-sensitive surface at the back of the eyeball. Convert light energy to nerve impulses. Made up of three layers of cells Receptor cells Bipolar cells Ganglion cells

The Blind Spot Blind spot: the part of the retina where the optic nerve leaves the eye There are no rods and cones (receptors) at this point

Rods Location: retina Can only detect black, white and shades of gray Respond to less light than do cones Night vision

Cones Location: Retina Can detect sharp images and colors Work best in daylight Most located in fovea

Trichromatic (3 color) Theory Cones are “tuned” to be sensitive to three different wavelengths of light (red, green, blue) which combine to form white Create any color by varying their brightness

Color-Blind Generally lack 1 of the 3 types of cones. Usually either the red or the green “Color Deficient”: not really Blind to color, just limited in the number of colors they see Inherited condition Seen more in males than females Many times the person doesn’t even realize that a problem exist!

Opponent-Process Theory Why do we see color “after images”? Color processing neurons oppose one another. Stimulation that turns on a green processing neuron, ensures that a red processing neuron will be off.

Hearing: The Nature of Sound Module 9: Sensation

Hearing Depends on sound waves or vibrations Sound waves pass through various bones in the inner ear 3 features: pitch, hertz, decibels

Loudness Decibels: measures loudness of sound waves Sound travels through the air at 1130 feet per second (770 mph)

Auditory Canal The opening through which sound waves travel as they move into the ear for processing Ends at the tympanic membrane (eardrum)

Ossicles Three tiny bones that pick up and transmit the sound vibration Hammer, anvil and stirrup Connect the eardrum to the cochlea (snail)

Sound Localization Determines which ear hears it first Determines which ear hears the louder and more intense sound Able to locate where the sound is coming from Slide # 25

Hearing Loss 30 million Americans have hearing problems 2 million are deaf Causes: birth defects, disease, injury, overexposure

Types of Hearing Loss Conduction deafness: caused by damage to the middle ear Nerve deafness: caused by damage to hair cells or the auditory nerve

Smell and Taste The chemical senses Nerve impulses travel through the olfactory nerve to the olfactory bulb in the brain, causing sensation of specific odors

Slide # 29 Taste Four basic tastes: sweet, sour, salty, bitter Food’s flavor results from these combinations: aroma, texture, temperature

Supertasters People who have greater taste sensibilities than others Supertasters have two to three times more taste buds than normal

Smell Chemical Sense 1,000 different odors are detectable Olfactory cells do not regenerate Taste and smell make: FLAVOR

Skin The skin is the largest sensory organ Touch: pressure, warmth, cold, pain 1.5 million receptors for touch and pressure, somatosensory cortex

Grouping Principles Brains are programmed to group objects to help us make sense of the world around us. 4 basic grouping principles: 1. Similarity: Items that look similar. 2. Proximity: Items that are close together. 3. Closure: See intact shapes when there are none. 4. Continuity: Object moves in particular direction.

Depth Perception The ability to see in 3 dimensions and judge distance. Visual Cliff: Lab device for testing depth perception in infants.

Optical Illusions Perceptions based on inappropriate assumptions between the appearance of a visual stimulus and its physical reality Muller-Lyer Illusion

Another Illusion Roger Shepard

An Impossible Figure Objects that can be represented in two- dimensional pictures may not be able to exist in three-dimensional space Bottom-up processing