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
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
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.