Perception_-_PSych_PPT
Page 1: Perception
Overview of perception concepts (Pg 59-65)
Page 2: Just Noticeable Difference / Difference Threshold
Definition: Smallest amount of change needed in a stimulus to detect a difference.
Essential Question: How much must a stimulus change before we perceive a difference?
Page 3: Weber's Law
Principle: The just-noticeable difference (JND) is proportional to the magnitude of the original stimulus.
Implication: Larger original stimuli require larger changes to be noticed.
Intensity relation: More intense stimuli need more change for detection.
Page 4: Weber's Law - Discriminable Analysis
Example values illustrating discriminability thresholds across senses:
Hearing: 0.2
Vision: 0.06
Touch: Shows discernible thresholds at varying levels.
Page 5: Weber's Law - Key Points
JND is a constant ratio of original stimulus intensity.
Percentage difference needed varies by sense:
Weight: 2-5% change to notice.
Brightness: 1-2% change needed.
Sound Volume: Approximately 1-5% change.
Page 6: Perceptual Theories
Theories that explain perception:
Signal Detection Theory
Top-Down Processing
Bottom-Up Processing
Page 7: Signal Detection Theory
States that detection depends on stimulus intensity and the observer's state.
Relates to both Weber's Law and individual factors affecting perception.
Page 8: Outcomes of Signal Detection Theory
Four outcomes based on observer response:
Hit: Signal detected.
Miss: Signal not detected.
False Alarm: Incorrectly perceived signal.
Correct Rejection: Signal absent, correctly not perceived.
Page 9: Signal Detection Theory - Definition and Outcomes
Definition: SDT explains decision-making based on sensory input strength and confidence.
Used under uncertainty, e.g., perceiving distances in fog.
Outcomes repeat the four situations described on Page 8.
Page 10: Top-Down Processing
Cognitive process using pre-existing knowledge to interpret sensory information.
Also known as conceptually driven processing.
Relies on prior knowledge and experiences for understanding.
Page 11: Top-Down Processing Example
Example of using familiarity with word shapes:
_voc_do
Dand_li_n
_clip_e
Tw_li_ht
Page 12: Bottom-Up Processing
Describes how sensory information is processed independently of prior knowledge.
Focuses on details and is largely automatic.
Page 13: Processing Strategies
Top-Down Processing: Uses prior knowledge for interpretation.
Example: Understanding a story by interpreting text details.
Bottom-Up Processing: Builds perception from sensory inputs.
Example: Anticipating song lyrics based on familiarity.
Page 14: Top-Down vs Bottom-Up Processing
Top-Down: Involves expectations and existing models for perception.
Bottom-Up: Analyzes sensory details without prior influence.
Page 15: Figure-Ground Principle
Cognitive function to distinguish figure from ground in visual scenes.
Page 18: Figure-Ground Relationship
Describes how visual fields are separated into figure (focus of attention) and ground (background).
Fundamental Gestalt principle for simplifying visual scenes.
Page 19: Gestalt Rules Overview
Gestalt rules entail principles for organizing sensory information into wholes.
Key Concept: "The whole is greater than the sum of its parts".
Page 20: Main Gestalt Principles
Proximity: Grouping close objects together.
Similarity: Grouping similar-looking objects.
Continuity: Perceiving smooth patterns.
Closure: Filling in gaps to see a complete figure.
Figure-ground: Recognizing focal objects against their background.
Page 22: Examples of Gestalt Principles
Objects grouped together appear as a single figure.
Continuation: Perceiving uninterrupted objects despite intersections.
Symmetry: Recognizing symmetrical arrangements around a center.
Page 23: Perceptual Constancy
Refers to perceiving familiar objects as stable despite sensory changes.
Types include:
Size Constancy: Perceiving constant size at different distances.
Shape Constancy: Maintaining perceived shape despite angle changes.
Color Constancy: Seeing the same color under varied lighting.
Page 26: Brightness Constancy Example
Illustrates how identical shades can appear differently due to environmental context.
Light conditions affect perceived brightness, e.g., a dark square in light vs a light square in shadow.
Page 27: Perceived Motion
Definition: Psychological experience of seeing movement through visual signals.
Involves interpreting visual cues, leading to perceived motion even when stationary.
Page 28: Key Points About Perceived Motion
Optical Illusions: Objects appearing to move due to misinterpretation of visual data.
Phi Phenomenon: Misinterpretation of rapidly flashing lights as movement.
Motion Parallax: Real-world observation of speed differences based on distance.
Page 30: Depth Cues
Visual signals that allow distance perception.
Binocular cues: Difference in perspective from two eyes (e.g., retinal disparity).
Monocular cues: Single-eye cues like linear perspective, texture gradient, and interposition.
Page 31: Examples of Monocular Cues
Relative Size: Larger objects appear closer.
Linear Perspective: Converging parallel lines suggest distance.
Interposition: Overlapping objects indicate positional closeness.
Texture Gradient: Denser textures suggest proximity.
Aerial Perspective: Distant objects appear hazy.
Page 32: Key Points About Binocular Cues
Retinal Disparity: Images are slightly different from each eye allowing depth perception.
Convergence: Eyes move inward focusing on nearby objects, relaying depth info to the brain.
Page 33: Culture and Perception
Cultural differences in perception, e.g., responses to the Muller-Lyer illusion based on environmental geometry experience.
Page 35: Extrasensory Perception (ESP)
Definition: Alleged ability to perceive information without known sensory channels.
Types: Telepathy, clairvoyance, precognition.
Scientific Consensus: ESP considered a paranormal phenomenon lacking robust evidence.