Sensation and Perception Lecture Notes

Introduction

• Topic: Sensation and Perception
• Presenter: Dr. Mark Atala
• Key areas covered:
  • Waves and wavelengths
  • Vision
  • Hearing
  • Other senses
  • Gestalt principles of perception

Definitions

• Sensation: Detection of sensory information by sensory receptors.
• Transduction: Conversion of sensory stimulus energy to an action potential.
• Five Senses:
  • Vision (sight)
  • Hearing (audition)
  • Smell (olfaction)
  • Taste (gustation)
  • Touch (somatosensation)

Key Concepts

Absolute Threshold

• Definition: Minimum stimulus energy needed for detection 50% of the time.
• Example: Eye can detect a candle flame from 30 miles away on a clear night.

Subliminal Messages

• Definition: Messages below the threshold of conscious awareness.
• Impact: Hidden messages have little effect on behavior outside laboratory settings.

Just Noticeable Difference (JND)

• Definition: Minimum change in stimuli needed to notice a difference.
• Example: Noticeability of light from a phone in different environments (theater vs. baseball game).
• Weber's Law: The difference threshold is a constant fraction of the original stimulus.

Perception

• Definition: Organization and interpretation of sensory information.
• Types of Processing:
  • Bottom-Up Processing: Perception built from sensory input.
  • Top-Down Processing: Interpretation influenced by prior knowledge and experiences.
• Sensory Adaptation: Tuning out constant stimuli (e.g., a ticking clock).

Attention and Perception

• Inattentional Blindness: Failure to notice visible stimuli due to lack of attention.
• Signal Detection Theory: Ability to identify a stimulus in the presence of background noise.

Cultural Influences on Perception

• Differences in susceptibility to visual illusions based on cultural context (e.g., Mueller-Lyer illusion).

Waves and Characteristics

Physical Characteristics of Waves

• Amplitude: Height of a wave.
• Wavelength: Length between peaks of a wave.
• Frequency: Number of waves passing a point in a given time, expressed in Hertz (Hz).
  • Longer wavelengths = lower frequency; shorter wavelengths = higher frequency.

Visible Spectrum

• Wavelengths visible to humans: 380 - 740 nanometers.
• Colors associated with wavelengths: Red (longer wavelengths) to Violet (shorter wavelengths).
• Mnemonic: ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet).

Hearing

• Frequency and pitch relationship: High frequency = high pitch, low frequency = low pitch.
• Audible range for humans: 20 - 20,000 Hz.
• Loudness measured in decibels (dB).
  • 60 dB = conversation; 120 dB = rock concert.
• Timbre: Quality of sound influenced by frequency, amplitude, and timing.

Visual System Anatomy

• Cornea: Transparent covering; focuses light.
• Pupil: Opening that changes size based on light/emotion.
• Lens: Curved structure that provides additional focus.
• Fovea: Part of the retina with densely packed cones (light-detecting cells).
• Rods and Cones: Rods detect low light; cones detect color and details.
• Blind Spot: Area where optic nerves connect, brain fills in gaps.

Theories of Color Vision

• Trichromatic Theory: Colors produced by combining red, green, and blue.
• Opponent Process Theory: Colors perceived in opposing pairs (e.g., red-green, blue-yellow).

Depth Perception

• Binocular Cues: Reliance on both eyes for depth perception (e.g., binocular disparity).
• Monocular Cues: Use of one eye (e.g., linear perspective, interposition).

Auditory System Anatomy

• Outer Ear: Pinna, auditory canal, tympanic membrane (eardrum).
• Middle Ear: Ossicles (malleus, incus, stapes).
• Inner Ear: Cochlea containing hair cells (auditory receptors).

Pitch Perception Theories

• Temporal Theory: Frequency coded by hair cell activity.
• Place Theory: Different basilar membrane portions sensitive to different frequencies.

Sound Localization

• Monaural and Binaural Cues: Used to determine the direction of sounds.
  • Intensity differences and timing differences help locate sounds.

Hearing Loss Types

• Conductive Hearing Loss: Age, genetic, or environmental causes.
• Sensorineural Hearing Loss: Failure to transmit neural signals from cochlea to brain.
• Cochlear Implants: Devices that stimulate auditory nerve directly.

Chemical Senses

• Taste (Gustation): Four basic tastes - sweet, sour, salty, bitter, plus umami and potentially fatty taste.
• Smell (Olfaction): Olfactory receptors in the nose detect odor molecules.

Touch and Pain Perception

• Types of touch receptors: Meissner's corpuscles, Pacinian corpuscles, Merkel's discs, and Ruffini corpuscles.
• Pain Types:
  • Inflammatory pain: Indicates tissue damage.
  • Neuropathic pain: Results from neuron damage.
• Congenital Analgesia: Inability to feel pain, leading to severe injuries.

Vestibular Sense

• Maintains balance and posture; relies on semicircular canals in the inner ear.

Gestalt Principles of Perception

• Figure-Ground Relationship: Segmenting visual world into figure and ground.
• Proximity: Grouping based on closeness.
• Similarity: Grouping based on shared characteristics.
• Continuity: Preferring smooth, flowing lines.
• Closure: Perceiving complete objects instead of parts.

Conclusion

• Reminder: For help with APA style writing, consult Dr. Atala's "Learn APA Style" resources.