 Sensation – stimulation of sense organs ◦ Absorption of energy by sensory organs  Perception – The selection, organization and interpretation of sensory input ◦ Involves transforming sensory input into something meaningful  Difference with regards to eye

 Sensation begins with a stimulus  For each sensation, there is a minimum level that humans are able to detect  Absolute Threshold- This is the minimum stimulus intensity an organism can detect. ◦ Examples:  Taste: one teaspoon of sugar in two gallons of water  Touch: the wing of a fly falling on your cheek from distance of one centimeter

 There is also a minimum level of difference between stimuli that humans are able to detect  Just Noticeable Difference – the smallest difference in stimulus intensity that specific sense can detect. ◦ Size of this is in proportion to size of initial stimulus  Weight lifting example

 Ability to detect a stimulus (or signal) can depend on certain factors.  Harder to detect a stimulus if a lot of “noise” around ◦ Example

 Subliminal Perception- The registration of sensory input without conscious awareness.  Question is: Even though we are not aware of a stimulus, can it still influence behavior?  Examples: Popcorn Target Person Study _Generally, these are still weak effects

 Sensory Adaptation- gradual decline in sensitivity after prolonged exposure ◦ In other words, “get used” to something  Apartment Stench Example  Class examples

 Cornea- Light enters eye through this “window”  Lens – clear structure that focuses light rays falling on retina ◦ Like actual lens- “focuses”  Pupil- opening in center of the eye that regulates amount of light passing into eye

 Images are projected upside down onto the retina  Retina- Processes information ◦ Absorbs light, processes images, sends visual info to brain ◦ Link to the brain ◦ Contains blind spot- hole in retina  Cannot see part of an image that falls on it

 Dark Adaptation- Eyes become more sensitive to light in low illumination ◦ Dark Theater example  Light Adaptation- Eyes become less sensitive to light in high illumination ◦ Theater parking lot example

 1.) Trichromatic Theory  2.) Opponent Process Theory

 Trichromatic Theory- human eye has three types of receptors with differing sensitivities to different wavelengths. ◦ These receptors are sensitive to wavelengths associated with red, green and blue ◦ Our eye combines colors  Support for theory ◦ Creation of other colors in art ◦ Color TV ◦ Color Blindness- deficiencies to distinguish between colors  Result of lacking in one of these channels or receptors (red, green, blue)

 Opponent Process Theory- Color perception depends on receptors that make antagonistic responses to three pairs of colors.  Three pairs of opponent colors: ◦ Red-green ◦ Yellow-blue ◦ Black-White  Support for theory: ◦ Complimentary afterimages- after staring at image for awhile, an image will persist when you look away consistent of complimentary colors

 As seen from optical illusions, the same visual input can result in very different perceptions ◦ Interpretations of sensory input can very  Sometimes perception depends on what we select to focus attention on: ◦ Inattentional blindness-

 Gestalt Psychologists- believe we perceive things as a whole (not just individual parts)  Some Gestalt Principles: ◦ 1.) Figure and ground ◦ 2.) Proximity ◦ 3.) Closure ◦ 4.) Similarity

This Principle states we divide images into the figure being looked at and the background

 This principle says that things near one another seem to belong together

 This principle states that people group elements to create sense of closure

 This Principle says that we tend to group things together that are similar

 Context Effect- The context in which a stimulus is seen can affect perception

 Stroop Effect-difficulty in identifying the colors in which names of colors are written. For example, if the word "red" is printed in green ink, people are likely to say "red" when asked the color of the printed word.

 Visual Agnosia- Inability to recognize familiar objects or faces. ◦ Often due to damage of occipital and/or temporal lobe of brain  Example Clip