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AP - Sensation & Perception

SENSATION & PERCEPTION

Key Concepts

  • Sensation: Detection of physical energy and conversion to neural signals.

  • Perception: Interpretation and understanding of sensory information.

Differences Between Sensation and Perception

  • Sensation is about raw data from the senses; perception is the interpretation of that data.

  • Example: Seeing the letter "A" (Sensation) vs. believing it represents a letter (Perception).

Processing Types

Bottom-Up Processing

  • Analysis starts with sensory input and builds up to perception.

  • Example: Recognizing the letter "A" as a collection of lines.

Top-Down Processing

  • Uses prior knowledge and experiences to interpret sensory information.

  • Perception can vary based on context and expectations.

Psychophysics

  • Studies the relationship between the physical properties of stimuli and the psychological experiences they evoke.

Thresholds

  1. Absolute Threshold: Smallest detectable level of stimulus (e.g., seeing a candle flame from 30 miles).

  2. Difference Threshold: Minimum difference between two stimuli for detection (Just Noticeable Difference or JND).

  3. Subliminal Threshold: Sensory input below the conscious threshold can still influence behavior.

Signal Detection Theory

  • Predicts how and when we detect weak stimuli amidst noise.

  • Influenced by personal experiences, expectations, and motivations.

Vision and Light

Light Characteristics

  • Wavelength: Determines color; each color corresponds to a specific wavelength.

  • Intensity: Determines brightness, related to amplitude.

  • Purity: Determines saturation; mixed light yields different perceptions.

How Vision Works

  1. Light enters through the cornea.

  2. Passes through the pupil and lens.

  3. Focused onto the retina, activating cones (color) and rods (light sensitivity).

  4. Converted into neural impulses sent via the optic nerve to the brain.

Color Vision

  • Trichromatic Theory: Three types of cones sensitive to red, green, and blue.

  • Opponent-Process Theory: Opposing color pairs contribute to color processing.

Visual Perception

  • Gestalt Principles: How we perceive objects as organized wholes rather than isolated parts (Proximity, Similarity, Continuity).

  • Figure-Ground Relationship: Differentiating between objects and the background.

Depth Perception

  • Ability to perceive the world in three dimensions based on cues from both eyes and single-eye cues (e.g. relative size, motion).

Auditory Perception

  • Sound processed via ear structures: outer ear, middle ear, inner ear (cochlea).

  • Distinction of sound characterized by frequency (pitch), intensity (loudness), and quality (timbre).

Theories of Pitch Perception

  1. Frequency Theory: Rate of nerve impulses corresponds to pitch; best for low pitches.

  2. Place Theory: Frequency is linked to specific places on the cochlea; best for high pitches.

Touch and Pain

  • Touch consists of pressure, warmth, cold, and pain sensors.

  • Gate-Control Theory and Neuromatrix Theory explain the perception of pain.

Taste and Smell

  • Taste: 5 basic tastes; influenced by chemical stimulation in taste buds.

  • Smell: Directly connects to memory areas in the brain and influences taste.

Sensory Interaction

  • One sense can influence another, enhancing perception (e.g., flavor, understanding of speech).

Implications of Subliminal Messaging

  • Messages below conscious awareness can affect behavior and perceptions, although not forceful.

Influences on Perception

  • Factors like context, beliefs, needs, and expectations shape how we perceive stimuli.