Introductory Psychology: Sensation Ap psychology: Unit v

Sensation Vision, hearing, smell, taste, touch, pain & body position Similarities? Transduce stimulus energy into neural impulses More sensitive to change than to constant stimulation Provide us with information regarding our environment Differences? Each requires a different form of stimulus energy Each sends information to a different region of the brain for processing

Sensation: Vision Part one

Vision: The Stimulus Input Light energy (electromagnetic energy) Two physical characteristics help to determine our sensory experience of light Wavelength The distance from one peak to another Determines HUE (color) Amplitude Height of each wave’s peak Determines INTENSITY (brightness)

Shorter wavelength – bluish colors Longer wavelength – reddish colors Great amplitude – bright colors Small amplitude – dull colors

Vision: The Structure of the Eye Cornea Location/Structure The clear bulge on the front of the eyeball Function Protects the eye Bends light towards a central focal point in order to provide focus

Vision: The Structure of the Eye Pupil/Iris Location/Structure Adjustable opening in the center of the eye Surrounded by the iris (small ring of muscle tissue; color) Function Controls the amount of light that is able to enter the eye In bright conditions the iris expands, making the pupil smaller In dark conditions the iris contracts, making the pupil larger

Vision: The Structure of the Eye Lens Location/Structure A transparent structure that is located behind the pupil Function Focuses image on the back of the eye (retina) Accommodation The process by which the eye’s lens changes shape to help focus near or far objects on the retina

Vision: The Structure of the Eye Lens Problems Nearsightedness Also known as myopia Eyeball may be too long Image focused in front of the retina Farsightedness Also known as hyperopia Eyeball may be too short Image focused behind the retina

Vision: The Structure of the Eye Retina Location/Structure A multilayered, light-sensitive surface located at the back of the eyeball Function Contains cells that convert light energy into nerve impulses Includes three layers of cells Receptor cells (photoreceptors – cones & rods) Bipolar cells Ganglion cells

Vision: The Structure of the Eye Cones Rods Number 6 million 120 million Location (in the retina) Center (fovea) Edge (periphery) Color sensitive Yes No Sensitivity in dim light? Low High Ability to detect sharp detail (acuity)? Photoreceptor Cells

Vision: The Structure of the Eye Bipolar Cells Receives message from the photoreceptors Transmits message to the ganglion cells, which are then considered “activated” Ganglion Cells The axons of the ganglion cells converge to form the optic nerve

Light energy  Rods & Cones  Bipolar cells  Ganglion cells

Vision: The Structure of the Eye Optic Nerve Location/Structure Nerve located at the back of the eyeball Function Sends visual information to the thalamus and then to the occipital lobes Where the optic nerve leaves the eye, there are no rods or cones, creating a blind spot

Vision: Visual Processing Feature Detectors Located in the visual cortex Nerve cells in the brain that respond to specific features Shape Angle Movement

Vision: Visual Processing Parallel Processing The processing of several aspects of a stimulus simultaneously The brain divides a visual scene into color, depth, form and movement

Visual Information Processing Feature Detection + Parallel Processing Color Motion Form Depth All processed separately but simultaneously

Vision: Color Vision Young-Helmholtz Trichromatic Theory (Hermann von Helmholtz & Thomas Young) The theory that the retina contains three different color receptors – red, green and blue When stimulated in combination, these receptors can produce the perception of any color Color Blindness? Dichromatic Color Vision Individuals lack one of three receptors; usually the red or green receptor

Vision: Color Vision Opponent-Process Theory of Color (Ewald Hering) The theory that opposing retinal processes enable color vision Red-Green Yellow-Blue Black-White Light that stimulates one half of the pair inhibits the other half For example, some cells are stimulated by green and inhibited by red, while others are stimulated by red and inhibited by green

Here's another example of creating an afterimage Here's another example of creating an afterimage. Can you put the fish in the bowl? Try this. Stare at the yellow stripe in the middle of the fish in the picture below for about 15-30 sec. Then move your gaze to the fish bowl. You should see a fish of a different color in the bowl. It helps if you keep your head still and blink once or twice after you move your eyes to the bowl. The afterimage will last about five seconds.

Stare at the eye of the red parrot while you slowly count to 20, then immediately look at one spot in the empty birdcage. The faint, ghostly image of a blue-green bird should appear in the cage. Try the same thing with the green cardinal, and a faint magenta bird should appear.

Sensation: Hearing Part two

Hearing: The Stimulus Input Sound energy Two physical characteristics help to determine our sensory experience of sound Wavelength/Frequency The distance from one peak to another Determines PITCH Amplitude Height of each wave’s peak Determines LOUDNESS

Shorter wavelength – high-pitch Longer wavelength – low-pitch Great amplitude – loud sounds Small amplitude – soft sounds

Hearing: The Structure of the Ear Outer Ear Relevant Structures Pinna Function Channels sound waves through the auditory canal to the eardrum (tympanic membrane)

Hearing: The Structure of the Ear Middle Ear Relevant Structures (Eardrum) Hammer, Anvil, Stirrup Function Transmits the vibrations of the eardrum through a piston made of 3 tiny bones Hammer, anvil, stirrup These bones then transmit the message to the cochlea

Hearing: The Structure of the Ear Inner Ear Relevant Structures Cochlea Basilar Membrane Function The incoming vibrations cause movement in the cochlea’s oval window, which then creates motion in the cochlea’s fluid This motion causes movement in the basilar membrane and its hair cells Eventually, the hair cells trigger an impulse in adjacent nerve fibers; converge to form the auditory nerve

Hearing: The Structure of the Ear

Hearing: Pitch Perception Place Theory In hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated We hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane Best explains our perception of high-pitched sounds

Hearing: Pitch Perception Frequency Theory In hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch Best explains our perception of low-pitched sounds

Hearing: Sound Localization

Hearing: Hearing Problems Conduction Hearing Loss Caused by damage to the mechanical system that conducts sound waves to the cochlea Sound vibrations cannot be passed from the eardrum to the cochlea Example Punctured eardrum Sensorineural Hearing Loss Caused by damage to the cochlea’s receptor cells or to the auditory nerves Also called nerve deafness

NERVE DEAFNESS CONDUCTION DEAFNESS

Sensation: The Other Senses Part three

Sensation: Olfaction (Chemical Sense) TO DISCUSS General structure Chemical sense Gender differences Connection to limbic system

Sensation: Gustation (Chemical Sense) TO DISCUSS Crudest sense General structure Chemical sense Average adult? Lifespan? Supertasters Gender differences

Instructions: Jelly Belly Activity In partners, you will take turns eating Jelly Bellies… Instructions for the EATER The eating partner MUST keep his or her eyes closed The eating partner MUST keep his or her nose plugged for the first few “chews” After 4-5 good chews, the eating partner should release his or her nose Instructions for the NON-EATER The non-eating partner should provide the eating partner with a Jelly Belly & silently note its flavor

Sensation: Skin (Somesthetic Sense) TO DISCUSS General structure Pressure? Other sensations? Sensation of pain Gate Control Theory Fast v. Slow Fibers

Sensation: Kinesthetic (Somesthetic) TO DISCUSS General structure Position & motion sensors

Sensation: Vestibular (Somesthetic) TO DISCUSS General structure Semicircular canals Otolith organs Planes of movement