Unit 4: Sensation and Perception

Module 16: Basic Principles of Sensation and Perception

Key Definitions

• Sensation: Activation of special receptors on sensory organs, allowing outside stimuli to become neural signals.
  
  

• Perception: Interpretation and organization of sensations into meaningful experiences.
  
  

Processing Types

• Bottom-Up Processing: Analyzing smaller features to build a complete perception; sensory input → brain processing.
  
  

• Top-Down Processing: Using prior knowledge, experience, and memory to interpret sensory input.
  
  

Attention and Awareness

• Selective Attention: Focusing on one stimulus while excluding others.
  
  

• Inattentional Blindness: Missing visible objects due to focused attention elsewhere.
  
  

• Change Blindness: Failing to notice changes after a visual interruption.
  
  

Transduction

• Converting stimulus energies (sights, sounds, smells) into neural impulses.
  
  

Psychophysics

• Study of how physical energy relates to psychological experience.
  
  

Thresholds

• Thresholds: Minimum stimulus needed for detection.
  
  

• Signal Detection: Thresholds vary per person and situation; detection influenced by experience, expectations, and state.
  
  

• Subliminal Stimulation: Below conscious threshold; may activate associations (priming).
  
  

• Difference Threshold: Minimum difference needed to detect stimuli 50% of the time.
  
  

  • Weber’s Law: Stimuli must differ by a constant proportion, not amount.
    
    

    • e.g., 100 lbs needs 5 lbs for noticeable difference.
      
      

• Absolute Threshold: Detecting something from nothing.
  
  

• Sensory Adaptation: Reduced sensitivity due to constant stimulation.
  
  

  • Sight differs due to constant eye movement.
    
    

  • Adaptive benefit: alerts us to novel stimuli.
    
    

Module 17: Influences on Perception

Perceptual Set

• Mental predisposition influenced by experiences, assumptions, and expectations; may prevent accurate perception.
  
  

Schemas

• Mental frameworks that organize and interpret information.
  
  

Context Effects

• Stimulus context influences interpretation.
  
  

  • Same stimulus → different perceptions in different situations.
    
    

  • Motivation & emotion affect perception.
    
    

Extrasensory Perception (ESP)

• Parapsychology: Study of paranormal phenomena.
  
  

Types of ESP

• Telepathy: Mind reading.
  
  

• Clairvoyance: Seeing distant events.
  
  

• Precognition: Seeing the future.
  
  

• Psychokinesis: Moving objects with the mind.
  
  

Experiments in ESP

• Daryl Bem & Charles Honorton: Ganzfeld experiments → 32% success rate; not replicable.
  
  

• Zener Cards: Created by Carl Zener; tested ESP (discredited due to flawed methods).
  
  

Module 18: Vision

Light Energy

• Wavelength: Distance between wave peaks; determines hue (color).
  
  

• Amplitude: Height of wave; determines brightness.
  
  

The Eye

• Pupil: Light enters here.
  
  

• Iris: Controls pupil size.
  
  

• Lens: Focuses image on retina (accommodation).
  
  

• Retina: Contains rods and cones; processes visual info.
  
  

• Sclera: White protective layer.
  
  

• Cornea: Transparent outer covering; aids focus.
  
  

Visual Acuity

• Acuity: Sharpness of vision.
  
  

• Nearsightedness: Difficulty seeing distant objects.
  
  

• Farsightedness: Difficulty focusing on nearby objects.
  
  

Retina Components

• Optic Nerve: Carries visual info to brain.
  
  

• Blind Spot: No rods/cones at optic nerve exit.
  
  

• Fovea: Center of retina; high cone concentration.
  
  

• Rods: Black, white, gray; peripheral & low-light vision.
  
  

• Cones: Centered, fine detail, color; require bright light.
  
  

Visual Information Processing

• Feature Detection (Hubel & Wiesel, Nobel Prize 1981): Neurons respond to shape, orientation, movement.
  
  

• Parallel Processing: Simultaneous processing of color, depth, form, movement.
  
  

Color Vision Theories

• Young-Helmholtz Trichromatic Theory: 3 cone types for red, green, blue.
  
  

• Opponent-Process Theory (Ewald Hering, 1878): Red-Green, Blue-Yellow, Black-White systems. Explains afterimages.
  
  

Visual Organization

• Gestalt: Whole > sum of parts; we integrate pieces into wholes.
  
  

Form Perception

• Figure-Ground: Distinguish object from background.
  
  

• Grouping:
  
  

  • Proximity: Nearness.
    
    

  • Similarity: Likeness.
    
    

  • Continuity: Smooth patterns.
    
    

  • Connectedness: Linked objects perceived as a unit.
    
    

Depth Perception

• Visual Cliff: Depth perception is partially innate (Gibson & Walk).
  
  

Binocular Cues

• Retinal Disparity: Difference in images between eyes → depth.
  
  

• Convergence: Eye muscle tension cues distance.
  
  

Monocular Cues

• Relative Size: Closer = larger.
  
  

• Interposition: Closer objects block others.
  
  

• Relative Clarity: Closer = clearer.
  
  

• Texture Gradient: Closer = more detail.
  
  

• Relative Height: Higher = farther.
  
  

• Relative Motion: Objects move relative to us.
  
  

• Linear Perspective: Parallel lines converge in distance.
  
  

• Light & Shadow: Dimmer = farther.
  
  

Perceiving Motion

• Smaller objects appear faster.
  
  

• Stroboscopic Motion: Illusion from rapid image sequence.
  
  

• Phi Phenomenon: Illusion from blinking lights.
  
  

Perceptual Constancy

• Objects remain consistent in perception despite sensory changes.
  
  

  • Applies to light, color, shape, size.
    
    

  • Color Constancy: Color perceived as constant under varying light.
    
    

Perceptual Illusions

• Misinterpretations due to brain’s typical organization of sensory info.
  
  

Visual Capture

• Vision dominates other senses.
  
  

Module 20: Hearing

Sound Waves

• Frequency: Cycles/sec; determines pitch.
  
  

• Pitch: High/low sound.
  
  

• Loudness: Measured in decibels, determined by amplitude.
  
  

• Amplitude: Height of sound wave.
  
  

• Sound waves → fluid waves → electrical impulses → brain.
  
  

Perceiving Pitch

• Place Theory: Different cochlea areas respond to different pitches.
  
  

• Frequency Theory: Membrane vibrates at sound frequency.
  
  

Hearing Loss

• Conduction: Damage to mechanical sound wave system.
  
  

• Sensorineural: Damage to cochlea’s receptors or auditory nerves.
  
  

Locating Sounds

• Differences in timing/loudness between ears help locate sound.
  
  

Touch

• Receptors detect pain, pressure, temperature.
  
  

• Pain perception varies; amplified by depression.
  
  

Gate Control Theory (Melzack & Wall)

• Spinal cord has small pain fibers and larger sensory fibers.
  
  

• Competing large fiber signals block small fiber pain signals.
  
  

Taste

• Chemical sense.
  
  

• 5 basic tastes; survival advantage in sweet/bitter sensitivity.
  
  

• Quick aversions from sickness.
  
  

Smell

• Chemical sense.
  
  

• Detected by receptors in nasal cavity.
  
  

• Carried by olfactory nerve.
  
  

• Strong link to emotion & memory.
  
  

Body Position and Movement

• Kinesthesis: Sense of body position/movement; sensors in muscles, joints, tendons.
  
  

• Vestibular Sense: Balance from semicircular canals & vestibular sacs. Fluid movement triggers receptors.
  
  

Sensory Interaction

• One sense can influence another.
  
  

• Taste + smell processed in temporal lobe.
  
  

Embodied Cognition

• Bodily sensations influence thoughts, judgments, preferences.
  
  

Human Factors Psychology

• Studies interaction between people and machines.
  
  

• Designs intuitive, safe technology (natural mapping).
  
  

• Aims to reduce human error.