Sensation and Perception Sensation: your window to the world Perception: interpreting what comes in your window. Bottom Up and Top Down Processing!

Sensory Adaptation Decreased responsiveness to stimuli due to constant stimulation. Not hearing the fan in the room. Smell of perfume diminishes Walk into a restaurant Do you feel your underwear all day?

Cocktail-party phenomenon The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. Form of selective attention.

Transduction Transforming signals into neural impulses. senses  thalamus,  other brain parts.

Sensation- Thresholds Absolute Threshold – minimum stimulation needed to detect a particular stimulus – defined as the stimulus needed for detection 50% of the time Difference Threshold or just noticeable difference (JND) – minimum difference between two stimuli that a subject can detect 50% of the time – increases with magnitude, need more difference with more weight (Weber’s Law) Signal Detection Theory – No single absolute due to outside factors – Sentry during war, new mommy, average homebody

Sensation- Thresholds Signal Detection Theory – predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) – assumes that there is no single absolute threshold – detection depends partly on person’s experience expectations motivation level of fatigue

Sensation- Thresholds Signal Detection Theory – Assumes TWO things going on: – 1. sensitivity to stimulus (physical) – 2. response bias – also called decision criterion (psychological) – Can measure & plot these in a Receiver Operating Characteristic curve (ROC curve)

Sensation- Thresholds Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion a constant for each sense: – light intensity- 8%, weight- 2% – tone frequency- 0.3% – Just noticable difference has a proportion to be met in order to sense difference

Weber’s Law Classic and still identified today but it did not account for extreme values….175 watt and a 200 watt… Ability to recognize difference diminishes….so in 1860s

Sensation- Thresholds Fechner’s Law- “upgrade” of Weber’s law – includes increase of jnd with extreme measures/magnitude – Adding the relationship of the perceived magnitude to physical intensity of a stimuli Same basic idea: – ½ pound book in 2lb vs. 60lb backpack – 1 voice in chorus of 10 versus 2 in 20

Sensation- Thresholds Steven’s Power Law - upgrade to Fechner (Fechner’s law didn’t work for pain*, other stimuli) – Strength of a sensation related to the intensity of the stimuli raised to some power – So pain like electric shock you will sense a a small change at higher intensities than at the lower intensities when more may be needed to recognize difference

Fechner Stevens

VisionVision Our most dominating sense. Visual Capture What we see surpasses what we feel, taste, smell, or hear….most seen in experiments with hearing

Phase One: Gathering Light The height of a wave gives us it’s intensity (brightness). The length of the wave gives us it’s hue (color). ROY G BIV – color schemas The longer the wave the more red. The shorter the wavelength the more violet.

Phase Two: Getting the light in the eye

Phase Three: Transduction

Transduction Continued Order is Rods/Cones to Bipolar to Ganglion to Optic Nerve. Sends info to thalamus- area called lateral geniculate nucleus (LGN). Then sent to cerebral cortexes. Where the optic nerves cross is called the optic chiasm.

Pathways from the Eyes to the Visual Cortex

Phase Four: In the Brain Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex. Feature Detectors. Parallel Processing We have specific cells that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.

Retina’s Reaction to Light Receptive fields – regions in which receptors respond to light Lateral inhibition – receptor (or neuron) making it’s neighbors less sensitive – Helps in things like edge detection

Visual Information Processing Feature Detectors neurons in the visual cortex respond to specific features – shape – angle – movement Stimulus Cell’s responses

Visual Information Processing Parallel Processing – simultaneous processing of several dimensions through multiple pathways – color – motion – form – depth

Visual Information Processing Scene Retinal processing: Receptor rods and cones  bipolar cells  ganglion cells Feature detection: Brain’s detector cells respond to elementary features-bars, edges, or gradients of light Abstraction: Brain’s higher-level cells respond to combined information from feature-detector cells Recognition: Brain matches the constructed image with stored images

Visual Information Processing Neural pathways (multiple!) – Optic nerve through optic chiasm (crossover), becomes the optic “tract” then… – Primary visual cortex (striate cortex) then splits into… – The “what” path (thru temporal lobes) – The “where” path (up into parietal lobes)

Color Vision Two Major Theories

Trichromatic Theory: Young–Helmholtz theory Three types of cones: Red Blue Green These three types of cones can make millions of combinations of colors.

Visual Information Processing – Color vision But Tri-chromatic didn’t explain afterimages or color-blindness! So… Opponent Process Theory – Black-white receptors (for brightness & saturation) – Red-green receptors (for hue) – Blue-yellow receptors (for hue)

Opponent Process- Afterimage Effect

Color-Deficient Vision People who suffer red- green blindness have trouble perceiving the number within the design

Opponent-Process theory The sensory receptors come in pairs. Red/Green Yellow/Blue Black/White If one color is stimulated, the other is inhibited.

Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON”“OFF” red green green red blue yellow yellow blue black white white black

Afterimages

Visual Information Processing – Color vision So who’s right??? – Turns out they’re both right: – Tri-chromatic theory works in the retina – Opponent process works in the higher visual processing parts of the brain – Together they explain what we know about color vision quite well.

Hearing Our auditory sense

We hear sound WAVES The height of the wave gives us the amplitude of the sound. The frequency of the wave gives us the pitch if the sound.

The Ear

Transduction in the ear Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. Everything is just vibrating. Then the cochlea vibrates. The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells. When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti. Sent then to thalamus up auditory nerve. It is all about the vibrations!!!

Pitch Theories Place Theory and Frequency Theory

Place Theory Different hairs vibrate in the cochlea when they different pitches. So some hairs vibrate when they hear high and other vibrate when they hear low pitches.

Frequency Theory All the hairs vibrate but at different speeds.

Deafness Conduction Deafness Something goes wrong with the sound and the vibration on the way to the cochlea. You can replace the bones or get a hearing aid to help. Nerve (sensorineural) Deafness The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible.

Touch Receptors located in our skin. Gate Control Theory of Pain

Taste We have bumps on our tongue called papillae. Taste buds are located on the papillae (they are actually all over the mouth). Sweet, salty, sour and bitter.

Vestibular Sense Tells us where our body is oriented in space. Our sense of balance. Located in our semicircular canals in our ears.

Kinesthetic Sense Tells us where our body parts are. Receptors located in our muscles and joints. Without the kinesthetic sense you could touch the button to make copies of your buttocks.