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.