Lecture Notes: Sensation and Perception

Key Concepts

Sensation

• Definition: Detection of sensory information by sensory receptors.
• Transduction: Conversion from sensory stimulus energy to action potential.
• Five Senses:
  • Vision
  • Hearing (Audition)
  • Smell (Olfaction)
  • Taste (Gustation)
  • Touch (Somatosensation)

Perception

• Definition: Organization, interpretation, and conscious experience of sensory information.
• Processes:
  • Bottom-up Processing: Perceptions are built from sensory input.
  • Top-down Processing: Influenced by knowledge, experiences, and thoughts.

Thresholds in Sensation

Absolute Threshold

• Minimum stimulus energy needed for detection 50% of the time.
• Examples: Detecting a candle flame from 30 miles on a clear night.

Subliminal Messages

• Messages below the threshold for conscious awareness.
• Can be processed and responded to without conscious awareness but have little effect outside the lab.

Just Noticeable Difference (JND)

• Amount of change needed in a stimulus for the change to be detected.
• Weber's Law: Difference threshold is a constant fraction of the original stimulus.

Sensory Adaptation

• Failure to perceive stimuli that remain constant over time.
• Example: Tuning out a ticking clock.

Attention and Perception

• Inattentional Blindness: Failure to notice something visible due to focus on another task.
• Signal Detection Theory: Identifying a stimulus within a distracting background.

Influences on Perception

• Influenced by beliefs, values, prejudices, expectations, and life experiences.
• Cultural differences, e.g., Western vs non-Western susceptibility to the Müller-Lyer illusion.

Vision

Waves and Wavelengths

• Amplitude: Height of a wave; related to sound loudness.
• Wavelength: Length from one peak to the next; related to frequency and color perception.
• Visible Spectrum: 380-740 nm for humans.

Color Vision Theories

• Trichromatic Theory: Colors produced by combining red, green, and blue.
• Opponent Process Theory: Colors coded in opponent pairs (e.g., black/white, red/green).

Visual System Anatomy

• Cornea: Transparent barrier, focuses light.
• Pupil: Light entry, size changes with light and emotion.
• Lens: Focuses images onto the fovea.
• Retina: Contains photoreceptors (cones and rods).

Depth Perception

• Binocular Cues: Use both eyes, e.g., binocular disparity.
• Monocular Cues: Require one eye, e.g., linear perspective, interposition.

Hearing

Sound Waves

• Frequency: Related to pitch.
• Amplitude: Related to loudness, measured in decibels.
• Timbre: Sound purity, affected by frequency, amplitude, timing.

Auditory System Anatomy

• Outer Ear: Includes pinna, auditory canal.
• Middle Ear: Contains ossicles (malleus, incus, stapes).
• Inner Ear: Cochlea, contains hair cells for auditory processing.

Pitch Perception Theories

• Temporal Theory: Frequency coded by sensory neuron activity level.
• Place Theory: Different basilar membrane parts sensitive to different frequencies.

Sound Localization

• Monaural and Binaural Cues: Determine sound location.

Taste and Smell

Taste (Gustation)

• Basic taste groupings: Sweet, sour, salty, bitter, umami, possibly fatty content.
• Taste buds have a 10-day to 2-week life cycle.

Smell (Olfaction)

• Olfactory receptor cells located in nasal mucus membrane.
• Dogs have more sensitive olfactory systems than humans.

Touch and Pain

Touch Receptors

• Meissner’s Corpuscles: Respond to pressure, low-frequency vibrations.
• Pacinian Corpuscles: Detect transient pressure, high-frequency vibrations.
• Merkel’s Discs: Respond to light pressure.

Pain Perception

• Inflammatory Pain: Signals tissue damage.
• Neuropathic Pain: Results from neuron damage.
• Congenital Insensitivity to Pain: Rare condition lacking pain perception.

Vestibular Sense

• Maintains balance and posture; interacts with proprioception and kinesthesia.

Gestalt Principles of Perception

• Figure-Ground Relationship: Segments visual world into figure and ground.
• Principles: Proximity, similarity, continuity, closure.

Conclusion

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