Thresholds Absolute Threshold- MINIMUM amount of sensory stimulation a person can normally detect Difference threshold-the amount of difference required between two stimuli for the brain to tell the difference between them. Sensory Adaptation- diminished sensitivity as a result of constant stimulation

VISION- Cornea- clear curved bulge at front of eye, first step in focusing of the light into the eye Retina-tissue at back of eyeball full of light receptor cells Iris- colored area of eye- muscle tissue that controls the size of the pupil opening Pupil-hole in eye that allows light into the eye Lens-transparent structure behind the pupil that focuses the light onto the retina – variable thicknesses Fovea- area on retina where the focus is greatest Optic Nerve- nerve from each eye that transfers visual information to the occipital lobe.

Peripheral Color Vision Experiment There are 2 Types of Receptor Cells in the eye: Rods and Cones Rods- located in the retina, can only “see” black, white and shades of gray but are better in low light conditions Cones- can “see” color, and sharp details but require more light in order to register objects (these are clustered in the fovea- where your vision is best) Peripheral Color Vision Experiment

Color Vision- Two Theories Trichromatic Theory- based on the wavelengths of colored light and additive color theory- primary colors are red, green and blue How do we explain colored after images then? Opponent Process Theory- our rods and cones work with pairs of receptors (red/green, blue/yellow and black/white) if one of the colors are stimulated the other part of the pair is turned “off” if you stare at a color then that receptor gets tired and needs to rest during which the opponent produce the afterimage while the original color receptors recover

Color Blindness Is caused by having non-functioning or too few cones for those specific colors (red/green colorblindness is most common) Very few people are truly color-blind- just color deficient.

Sensory Input AUDITORY- Ear Canal- pathway into the inner ear Eardrum- tissue barrier that transfers sound waves to the ossicles Ossicles – (Little Bones, hammer, anvil and stirrup) 3 tiny bones that transfer sound waves from eardrum to cochlea Cochlea- snail-shaped fluid filled structure that converts soundwaves to nerve impulses Auditory Nerve- nerve that takes sound input to the temporal lobe for processing

Sound Location Hunting Fox Human ears are separated by about 7-8 inches Sounds reach one of our ears microseconds before the other ear and one ear hears a slightly louder sound-the combination of the two informs the brain of the location of the sound. Hunting Fox

Pitch- frequency of sound waves – determines highness or lowness Hertz- measure of waves per second Decibels- height of the sound wave (determines volume)

4 Basic Tastes + 1 Salty- Salt is necessary for enzymatic processes without salt we would die Sweet- sweet is associated with energy and our bodies process it for fuel Sour- typically means food is spoiled or has been comprised with bacteria Bitter- typically indicates toxic or poisonous substances Umami- Japanese for “yummy” – responds to glutamates in food- it is its own category recent addition

Smell Skittles Experiment Olfactory Cells in our nasal passages pick up tiny molecules in the air that are dispersed – these are smells. Taste and Smell are related – without our olfactory cells our taste would be limited to the previous tastes – there is no “cherry” receptor. When we eat, the molecules from our food reach our nasal passages from the back of the throat allowing our olfactory cells to inform the brain what “flavor” it is. Olfactory cells do not regenerate when damaged- which is why older people have limited smell/taste capabilities Skittles Experiment

Perceptual Organization Gestalt-Looking at the BIG picture- instead of focusing on the smaller parts – the focus is on the “whole”. 4 types of Gestalt Organization Similarity- Grouping things that look like each other Proximity- The closer items are too each other, the more likely we are to group them Closure- The Brain fills in any gaps in our perceptual field (why we don’t see our blind spots) because it prefers a complete picture to bits and pieces Continuity- Once a moving object has been noticed- the brain assumes it will continue moving in that direction

Perception -Receiving and interpreting sensory information Expectations play a large role... 5 Types of Constancy 1. Size Constancy 2. Color Constancy 3. Brightness Constancy

5 Types of Constancy cont. 4. Shape Constancy- 5. Space Constancy- DEPTH PERCEPTION Visual Cliff Experiment Visual Cliff #2

Depth Perception cont. Retinal Disparity- (binocular) 3 Monocular Ways 1. Texture Gradient- 2. Size- (function of size constancy) 3. Overlap-

Illusions Müller-Lyer illusion- Reversible Figures-