Chapter 5
Sensation and Perception
Chapter Overview
Basic Concepts of Sensation and Perception:
Sensation
Perception
Bottom-up and Top-down Processing
Transduction
Absolute Threshold
Subliminal Stimulation
Difference Threshold (Just Noticeable Difference)
Weber's Law
Sensory Adaptation
Perceptual Set
Influence of Context, Motivation, and Emotion
Vision:
Light Energy (Wavelength, Hue, Intensity)
The Eye's Structure (Cornea, Pupil, Iris, Lens, Retina, Fovea, Optic Nerve, Blind Spot)
Receptors (Rods and Cones)
Eye-to-Brain Pathway
Color Vision Theories (Young-Helmholtz Trichromatic, Opponent-Process)
Feature Detectors and Supercells
Parallel Processing
Perceptual Organization (Gestalt Principles, Figure-Ground, Grouping - Proximity, Continuity, Closure)
Depth Perception (Visual Cliff, Binocular Cues - Convergence, Retinal Disparity; Monocular Cues - Relative Height, Relative Size, Interposition, Relative Motion, Linear Perspective, Light and Shadow)
Motion Perception
Perceptual Constancy (Color, Shape, Size)
Perceptual Interpretation (Innate vs. Learned perception)
Experience and Visual Perception (Critical Periods, Sensory Restriction)
Perceptual Adaptation
The Nonvisual Senses:
Hearing (Audition):
Sound Waves (Decibels)
Decoding Sound Waves (Eardrum, Middle Ear Bones, Cochlea, Hair Cells, Auditory Nerve, Thalamus, Auditory Cortex)
Hearing Loss (Sensorineural, Conduction)
Locating Sound
Touch:
Four Distinct Skin Senses: Pressure, Warmth, Cold, Pain
Other sensations are variations of these basic senses.
Pain:
A biopsychosocial event; not triggered by a singular stimulus or specialized receptors.
Reflects both bottom-up sensations and top-down cognition.
Biological Influences:
Nociceptors: Sensory receptors detecting hurtful temperatures, pressure, or chemicals.
Brain neural networks process sensations to produce pain perception.
Genetic and physical characteristics.
Brain-created pain: Phantom limb sensation, Tinnitus, Phantom sights/tastes.
Natural painkillers: Endorphins.
Psychological Influences:
Attention focused on pain significantly impacts perception.
Memory of pain can be edited; remembered pain may differ from experienced pain.
Social-Cultural Influences:
Pain perception varies with social situations and cultural traditions.
Empathy: Feeling more pain when others appear to be in pain.
Controlling Pain:
Physical and psychological treatments: drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation training, meditation, thought distraction.
Endorphins: Natural painkiller released by the brain, providing a soothing effect.
Placebos: Dampen the central nervous system's attention and responses to pain.
Combining endorphins and distraction: Activates brain pathways to decrease pain and increase tolerance.
Hypnosis: A social interaction where suggestions are made about perceptions, feelings, thoughts, or behaviors.
Inhibits pain-related brain activity, though it doesn't block sensory input itself; it blocks attention to stimuli.
Explained by social influence theory and dissociation theory (posthypnotic suggestions).
Example: Ernest Hilgard's experiment with arm in ice bath showing dissociation.
Taste (Gustation):
Five basic sensations: Sweet, Sour, Salty, Bitter, Umami.
Provides pleasure and aids survival.
Influenced by learning and expectations.
Survival Significance of Tastes:
Sweet: Energy source.
Salty: Sodium essential for physiological processes.
Sour: Potentially toxic acid.
Bitter: Potential poisons.
Umami: Proteins for growth and tissue repair.
Mechanism:
Chemical sense.
Tongue bumps contain $200+$ taste buds.
Each bud has $50-100$ taste receptor cells that catch food chemicals and release neurotransmitters.
Receptors react to different food molecules and send messages to the brain.
Smell (Olfaction):
An old, primitive sense; olfactory neurons bypass the thalamus.
Mammalian ancestors relied on smell for food, predators, and pheromones.
Odor molecules come in many shapes and sizes.
Smell's appeal is partly based on learned associations and can evoke strong feelings, memories, and behaviors.
Olfactory receptors can produce different patterns to identify an estimated trillion different odors, aided by biology and learned associations (e.g., mother-newborn, romantic partners, predator scents).
Information from taste buds registers close to where the brain receives smell information, explaining why smell can trigger memory.
Body Position and Movement:
Kinesthesia: System for sensing the position and movement of individual body parts.
Sensors in joints, tendons, and muscles.
Key brain area: Cerebellum.
Vestibular Sense: Sense of body movement and position, including balance.
Semicircular canals and vestibular sacs in the inner ear.
Hair-like receptors in these structures respond to fluid movement caused by head/body movement.
Key brain area: Cerebellum.
Can be fooled by misleading cues.
Sensory Interaction:
Principle that one sense may influence another (e.g., smell enhances taste, touch influences taste, hearing and vision interact).
Sensation and perception exist on a continuum.
Brain circuits for bodily sensations interact with those for cognition.
Embodied Cognition: Influence of bodily sensations, gestures, and other states on cognitive preferences and judgments; brain blends inputs from multiple channels.
Synesthesia: A condition where one type of sensation produces another (e.g., seeing colors when hearing sounds); occurs when brain circuits for two or more senses become joined.
Summarizing the Senses (Table Format - Receptors can be found above):
Vision: Source - Light waves striking the eye; Receptors - Rods and cones in the retina; Key Brain Areas - Occipital lobes.
Hearing: Source - Sound waves striking the outer ear; Receptors - Cochlear hair cells (cilia) in the inner ear; Key Brain Areas - Temporal lobes.
Touch: Source - Pressure, warmth, cold, harmful chemicals; Receptors - Receptors (including pain-sensitive nociceptors), mostly in the skin, which detect pressure, warmth, cold, and pain; Key Brain Areas - Somatosensory cortex.
Taste: Source - Chemical molecules in the mouth; Receptors - Basic taste receptors for sweet, sour, salty, bitter, and umami; Key Brain Areas - Frontal/temporal lobe border.
Smell: Source - Chemical molecules breathed in through the nose; Receptors - Millions of receptors at top of nasal cavities; Key Brain Areas - Olfactory Bulb.
Kinesthesia (Position and Movement): Source - Any change in position of a body part, interacting with vision; Receptors - Kinesthetic sensors in joints, tendons, and muscles; Key Brain Areas - Cerebellum.
Vestibular Sense (Balance and Movement): Source - Movement of fluids in the inner ear caused by head/body movement; Receptors - Hair-like receptors in the ears' semicircular canals and vestibular sacs; Key Brain Areas - Cerebellum.
Perception Without Sensation? (Extrasensory Perception - ESP):
Definition: The controversial claim that perception can occur apart from sensory input.
Claims Include:
Telepathy: Mind-to-mind communication.
Clairvoyance: Perceiving remote events.
Precognition: Perceiving future events.
Linked to ESP: Psychokinesis (mind moving matter).
Research and Experiments:
Most research psychologists and scientists are skeptical due to difficulty in controlled, reproducible testing.
Daryl Bem's experiments suggested participants could anticipate future events, but critics found methods flawed.