AP PSYCHOLOGY: UNIT V Introductory Psychology: Sensation

Sensation Vi sion, 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

PART ONE Sensation: Vision

Vision: The Stimulus Input 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)

What makes up a light wave?

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 ConesRods Number6 million120 million Location (in the retina) Center (fovea) Edge (periphery) Color sensitiveYesNo Sensitivity in dim light?LowHigh Ability to detect sharp detail (acuity)? HighLow 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

PART TWO Sensation: Hearing

Hearing: The Stimulus Input 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

Why do we have 2 ears?

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

CONDUCTION DEAFNESS NERVE DEAFNESS

PART THREE Sensation: The Other Senses

Why do we study smell and taste together? SENSORY INTERACTION: the principle that one sense may influence another.

Sensation: Olfaction (Chemical Sense) Cilia Receptor cells that collect molecules of odor. Olfactory bulbs Receives an electrical signal and generates a “code” that is sent to the brain for interpretation. We can detect over 10,000 odors and odors have the power to evoke memories and feelings!

So can we smell a difference between men & women? Well….yes and no. Pheromones  Chemicals excreted by humans and other animals that act as signals to, and elicit certain patterns of, behavior from members of the same species.  Used by animals to mark off territories and to signal sexual receptivity. Karl Grammer  Suggested that humans, although not consciously aware of it, respond to pheromones when it comes to mating.

Sensation: Gustation (Chemical Sense) We have bumps on our tongue called papillae. Taste buds are located on the papillae. Sweet, salty, sour, bitter and recently umami (savory). Bitterness detectors – critical because most poisons are bitter. Sour detectors – detect bad foods. Built-in salt and sugar needs for survival

Sensation: Skin (Somesthetic Sense) Receptors located in our skin Three types of touch Pressure Pain Temperature Gate control theory - Contends that there is an area in the spinal cord that can act like a “gate” and either inhibit pain messages or transmit them to the brain

Phantom Limb Pain Phantom limb pain is a frequent complication of amputation. Client complains of pain at the site of the removed body part, most often shortly after surgery.

Sensation: Kinesthetic (Somesthetic) Tell us where are body parts are Receptors are located in our Muscles Joints Tendons

Sensation: Vestibular (Somesthetic) Tells us where our body is orientated in space Our sense of balance Located in our semicircular canals in our ears