Sensation Module 9

I. Basic Definitions Sensation – Awareness of the world around you via your senses and nervous system. Bottom-up Processing – Focuses on new raw material entering through our eyes, ears and other senses. Perception – Interpretation of incoming sensory information. Top-down Processing – Draws on our experiences and expectations to interpret sensations.

II. Thresholds Absolute Threshold – The minimum stimulation required to detect a stimulus 50% of the time. Ex: Seeing the dimmest star in the sky or the least amount of garlic you taste in spaghetti sauce Difference Threshold – (Just Noticeable Difference) The minimum difference a person can detect between two stimuli 50% of the time. Ex: How much do you have to turn up the radio before it sounds louder? Weber’s Law – The stronger the sensation, the more change required to notice a difference.

II. Thresholds Signal Detection Theory – Prediction of when we will detect the presence of a faint stimulus (signal) amid background stimulation (noise) Stimulus variables (How bright is the blip?) Environmental variables (Are there distracting noises?) Personal variables (Was the person properly trained?)

III. Sensory Adaptation Sensory Adaptation – Diminished sensitivity as a result of constant stimulation. Examples: Cold water of a swimming pool Smell in the biology room Wearing jewelry Can you think of some?

IV. Selective Attention Selective Attention – Ability to focus on one stimuli at a time. Examples: Old woman/young woman picture Blocking out extra noises while reading Having a conversation at a concert Can you think of some?

V. The Visual System A Nature of Light You must have light to have sight (lightwaves) Wave length (Color)- ROY G. BIV (Long to short waves) Amplitude (height) – Brightness (Taller waves produce brighter colors)

V. The Visual System Cornea – Clear curved bulge on the front of the eye. Iris – Colored part of eye, regulates the size of the pupil to let the right amount of light in. Pupil – Black part of eye, hole in the iris, lets light into the eye.

V. The Visual System Lens – Transparent structure behind the pupil, changes to focus images on the retina. Near-Sighted – Can see near, image tries to focus in front of the retina Far-Sighted – Can see far, image tries to focus behind the retina

V. The Visual System Retina – Processing center on the back surface of the eye. Rods – Receptor cells that detect only black, white and gray, respond in low light Cones – Receptor cells that detect details and color, require more light

V. The Visual System Fovea – Central focus point of the retina (point where vision is the best) Bipolar Cells – Middle layer of the retina Ganglion Cells – Top layer of the retina, axons of these cells form the optic nerve Optic Nerve – Carries visual information from the eye to the occipital lobes of the brain Blind Spot – Point where the optic nerve exits the eye (no receptor cells)

V. The Visual System Color Vision Tri-Chromatic Theory – All color is based on a combination of three colors (red, green and blue – Additive color mixing) Opponent Process Theory – Color is processed in opposite pairs (red-green, yellow-blue, black-white). If one half is stimulated, the other is inhibited. This explains color after-images.

VI. Hearing The Nature of Sound Sound is vibration in the form of waves Wavelength – Pitch (expressed in hertz) Wave amplitude – Loudness (measured in decibels)

VI. Hearing The loudness of sound is measured in decibels. Every 10- decibel increase represents a tenfold increase in loudness (a 20-decibel increase is 100 times louder, and a 30-decibel increase is 1000 times louder!). Prolonged exposure to sounds of 85 or more decibels can permanently damage receptor cells in the ear and cause hearing loss.

VI. Hearing Auditory Canal – Opening where sound enters the ear. Eardrum – Tiny barrier, transfers sound vibrations to the middle ear. Ossicles – 3 tiny bones that transfer sound waves from the eardrum to the cochlea (hammer, anvil, stirrup) Cochlea – Major organ of hearing, snail-shaped, bony, fluid-filled structure where sound waves are changed to neural impulses. Hair cells – Receptor cells for hearing, convert energy to neural impulses. Auditory nerve – Carries sound information from the ears to the temporal lobe.

VI. Hearing

VI. Hearing When a sound originates from your right, as in this figure, it reaches your right ear slightly faster and slightly louder than it reaches your left ear. Your brain calculates the differences to locate the source of the sound. Sometimes it is difficult to tell if a sound is coming from directly ahead of you or directly behind you, because sounds in this plane reach both ears at the same time and with equal intensity.

VII. Other Senses Taste (Chemical Sense) Taste receptors detect four tastes: Salty Sweet Sour Bitter Taste buds replace themselves when damaged

VII. Other Senses Smell (Chemical Sense) Olfactory Cells – Receptor cells for smell Thousands of odors are detectable Olfactory cells do not replace themselves when damaged, therefore sense of smell declines with age

VII. Other Senses Touch Four basic skin senses Pain Warmth Cold Pressure Pain is a form of protection and therefore important When cold and warm receptors are stimulated at the same time, the result is an eerie sensation of hot.

VII. Other Senses Body Senses Kinesthetic Sense – Provides information on body’s position and movement (receptor cells are in the muscles and joints.) Vestibular Sense – Located in the inner ear, provides information about overall orientation and balance.