Sensation and Perception class

Sensation and Perception

• Sensation: Stimulation of sense organs by stimuli.

• Perception: Organization and interpretation of sensory input.

• Transduction: Conversion of stimuli into neural information.

Sensory Limits

• Absolute Threshold: Minimum intensity for detection.

• Difference Threshold (JND): Smallest detectable difference between stimuli, proportional to initial intensity (Weber-Fechner Law).

Sensory Thresholds

• Vision: Candle flame seen at 30 miles.

• Hearing: Tick of a watch from 20 feet.

• Taste: 1 tsp sugar in 2 gallons water.

• Smell: 1 drop perfume in a three-room apartment.

• Touch: Wing of a bee falling 1 cm on cheek.

Sensory Adaptation

• Definition: Decreased sensitivity to a constant stimulus; affected by fatigue or repeated exposure.

Vision

• Light: Electromagnetic radiation; wavelength determines color.

• Eye Structure: Light passes through the cornea, iris, lens, and into the retina (contains rods and cones).

• Optic Nerve: Lacks photoreceptors, creating a blind spot.

Photoreceptors

• Rods: Peripheral vision, sensitive to light; approx. 100 million.

• Cones: Color detection; approx. 6 million.

Color Vision

• Trichromatic Theory: Three cone types (red, blue, green) combine to create colors.

• Opponent-Process Theory: Color perception involves complimentary pairs.

• Color Deficiency: Common in males; typically red-green deficiency.

Information Processing

• Bottom-Up: Processing sensory info without prior knowledge.

• Top-Down: Influenced by prior knowledge.

• Contextual Perception: Perception influenced by surrounding context.

Perceptual Set and Influences

• Perceptual Set: Tendency to perceive based on past experiences.

• McGurk Effect: Visual cues influence auditory perception.

Gestalt Theory

• Organizes sensory messages into wholes (e.g., Figure-Ground, Laws of Proximity, Similarity).

Depth Perception

• Monocular Cues: Depth perception with one eye; Binocular Cues: Requires two eyes.

Illusions and Impossible Images

• Examples include various visual illusions and M.C. Escher’s impossible figures.