Sensation and Perception Chapter 4, Section 1
Sensation Stimulation of sensory receptors and transmission of sensory information to the central nervous system.
Perception Psychological process through which we interpret sensory stimulation.
Absolute Threshold The weakest about of stimulus that can be sensed. Different in humans and animals Differ among humans
Absolute Thresholds for Humans SenseStimulusReceptorsThreshold VisionElectromagnetic energy Rods and Cones in the retina A candle viewed from a distance of about 30 miles on a dark night HearingSound WavesHair cells of the inner ear The ticking of a watch from about 20 feet away in a quiet room SmellChemical substances in the air Receptor cells in the nose About one drop of perfume in diffused throughout a small house TasteChemical substances in saliva Taste buds on the tongue About 1 teaspoon of sugar dissolved in 2 gallons of water TouchPressure on the skinNerve endings in the skin The wing of a fly falling on a cheek from a distance of about 0.4 inch
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Difference Threshold The minimum amount of difference that can be detected between two stimuli
Signal Detection Theory Method of distinguishing sensory stimuli that takes into account not only their strengths but also such elements as the setting, your physical state, and your mood and attitudes Also considers motivations, expectations, and learning
Sensory Adaptation The process by which we become more sensitive to weak stimuli and less sensitive to unchanging stimuli Living in the city you adapt to traffic noise (unchanging stimuli) Walking into a dark room and adapting to being able to see (week stimuli)
Vision Light – electromagnetic energy Not all light is visible to humans Sunlight can be broken down by colors, through water vapor (rainbow) or glass structures (prisms). The main colors of the structure from longest to shortest wavelengths are Red, Orange, Yellow, Green, Blue, Indigo, and Violet
The Eye Pupil – opening in the colored part of the eye, which adjusts to amount of light entering the eye. (pupil experiment) Lens – adjusts to the distance of objects by changing thickness (hold a finger at arms length and bring it slowly to your nose, fell the tension a the thickness of the lens adjusts to keep the finger in focus) squinting is adjusting the thickness of the lenses in the eye. Retina- the sensitive surface that acts as film in a camera, consists of neurons –Photoreceptors, a nerve then carries the visual input to the brain.
The Eye (continued) The Blind Spot- the point where the optic nerve leaves the eye. Draw two circles the size of a dime approx. four inches apart on a piece of paper. Hold at arms length, cover your left eye, and stare with your right eye. move the drawing toward your face until the circle on the right vanishes BLIND SPOT
The Eye (continued) Rods and Cones – photo receptors- Rods are sensitive to brightness of light, cones provide color vision. Dark and light Adaptation- adjusting to low light (dark adaptation improves up to 45 minutes), adjusting to bright light may seem to hurt ( a minute or two) Visual Acuity- sharpness, details in normal light. (vision test) nearsighted- harder to see far away farsighted- need to be further away from an object
Color Vision People with normal color vision see any color in the spectrum of visible light. Do and cats see fewer colors Insects see a wider variety of colors Color circle- colors of the spectrum, colors across from one another are complementary
Color Vision After images- if color vision is working properly if you look a certain images long enough you see and images complementary color
Color Blindness Partially or totally unable to distinguish colors due to a malfunction of cones. Totally color blind see only black and white Partially color blind see some colors, i.e. difficulty distinguishing red and green.