3.1 Principles of Sensation

Sensation vs. Perception

• Sensation: Raw data from our five senses.

• Perception: Interpretation of sensory information.

Gestalt Principles

• Figure and Ground:

  • Objects of focus (figure) vs. background.

• Continuation:

  • Continuation of an object or shape.

  • Example: Arrow on exit sign leads the gaze outward.

• Closure:

  • Filling in gaps to complete familiar objects.

  • Example: Black lines forming an incomplete airplane still perceived as an airplane.

• Similarity:

  • Grouping similar objects together.

  • Example: A pattern of similar objects forms one larger object.

• Proximity:

  • Grouping objects that are close together.

  • Example: Closer objects appear as a singular image.

• Symmetry:

  • Symmetrical objects perceived as one.

Depth Perception

• Binocular Cues: Require two eyes.

  • Convergence: Eyes move inward for near objects and straighten for distant objects.

  • Retinal Disparity: Each eye sees a different part of an object, providing depth.

• Monocular Cues: Require one eye.

  • Relative Size: Closer objects appear larger.

  • Interposition: Objects blocked by others are farther away.

  • Relative Height: Higher objects appear farther away.

  • Shading and Contour: Hazy/less detailed parts are farther away.

  • Texture and Gradient: Detailed objects are closer, blurry objects are farther.

  • Linear Perspective: Parallel lines converge in the distance.

  • Motion Parallax: Closer objects move faster; distant objects move slower.

Sensory Transduction

• Absolute Threshold: Minimum stimulation needed to detect a stimulus.

• Signal Detection Theory: Predicts detection of weak signals near the absolute threshold.

  • Hit: Signal present, and detected.

  • Miss: Signal present, but not detected.

  • False Alarm: Signal not present, but detected.

  • Correct Rejection: Signal not present, and not detected.

Sensory Adaptation vs. Habituation

• Sensory Adaptation:

  • Reduced sensitivity to a continuous stimulus.

  • Example: Not smelling a candle after a while.

• Habituation:

  • Reduced response to repeated exposure.

  • Example: Drug users needing higher doses for the same effect.

Difference Threshold (Just Noticeable Difference)

• Definition: Minimum change between two stimuli to detect a difference.

• Weber-Fechner's Law: Two stimuli must differ by a constant percentage, not a constant amount.

3.2 Principles of Perception

Perceptual Constancy

• Size Constancy: Objects perceived as the same size.

• Color Constancy: Perception of color remains the same despite lighting changes.

• Shape Constancy: Perceive objects as the same shape despite movement.

• Lightness Constancy: Perceive shading (black, white, gray) consistently.

Perceptual Sets and Schemas

• Perceptual Sets: Focus on certain aspects of stimuli based on prior knowledge.

• Schemas: Cognitive frameworks based on experiences.

  • Example: Birthday party schema helps understand general activities at future parties.

Influence of Emotions and Culture

• Emotional State: Positive emotions lead to positive perceptions, and vice versa.

• Cultural Influence: Cultural upbringing influences perception of shapes and angles.

Optical Illusions

• Müller-Lyer Illusion: Lines with different arrowheads appear to be of different lengths due to perceptual sets.

3.3 Visual Anatomy

Eye Structure

• Sclera: White, fibrous tissue protecting the eye.

• Cornea: Transparent layer, allows light to bend.

• Aqueous Humor: Fluid maintaining pressure in the eye.

• Iris: Ring-shaped membrane controlling eye color and light entry.

• Pupil: Dark part of the eye, light passes through.

• Lens: Focuses light, biconvex shape.

• Vitreous Humor: Gel-like fluid maintaining eye shape.

• Retina: Light-sensitive cells converting light to neural impulses.

• Choroid: Supplies oxygen and nutrients to retinal cells.

• Optic Nerve: Sends neural impulses from eye to brain.

Photoreceptors

• Rods: Located on the outer edge of the retina, see in dim light.

• Cones: Located in the fovea, enable clear vision and color perception.

Eye Conditions

• Astigmatism: Irregularly shaped cornea affecting focus.

• Cataracts: Cloudy lens causing blurry vision.

Color Perception

• Trichromatic Theory: Perceive color through combinations of three receptors (red, green, blue).

• Opponent Processing Theory: Neurons become excited or inhibited due to complementary color pairs (red-green, blue-yellow, black-white).

Color Blindness

• Achromatism: Only see black, white, and gray due to a lack of cones.

• Dichromatism: Confuse certain colors due to two functioning cone types.

• Trichromatism: Normal color vision.

Synesthesia

• Definition: Neurological condition where stimulating one sense triggers another.

  • Example: Hearing sounds and seeing colors.

3.4 Visual Perception

Processing Types

• Top-Down Processing: Using prior knowledge to interpret new information.

• Bottom-Up Processing: Interpreting unfamiliar information as it comes in.

Examples

• Proofreader's Illusion: Skipping over spelling errors because of familiarity.

• Ambiguous Images: Different interpretations based on prior knowledge.

  • Example: Bird vs. bunny image.

3.5 Auditory Sensation and Perception

Ear Structure

• Pinna: Outer part, directs sound into the auditory canal.

• Auditory Canal: Funnels sound to the eardrum.

• Eardrum: Vibrates, converting sound into mechanical vibrations.

• Ossicles: Amplify sound in the middle ear.

  • Malleus (Hammer)

  • Incus (Anvil)

  • Stapes (Stirrup)

• Oval Window: Sends amplified waves into the inner ear.

• Cochlea: Fluid-filled, converts vibrations into electrical impulses.

  • Basilar Membrane: Vibrates, causing stereocilia to move.

  • Stereocilia: Tiny hair cells that convert vibrations to impulses.

• Organ of Corti: Contains sensory receptors for hearing.

• Semicircular Canals: Fluid-filled, help with balance.

Sound Waves

• Frequency: Determines pitch (highness or lowness).

• Amplitude: Determines loudness (strength of wave).

Theories of Pitch Perception

• Place Theory: Different hair cells respond to different frequencies based on location.

  • Base of Cochlea: Higher-pitched sounds.

  • Apex of Cochlea: Lower-pitched sounds.

Hearing Loss

• Sensorineural Hearing Loss: Damage to cilia and auditory nerve.

• Conductive Hearing Loss: Blockage preventing sound from reaching inner ear.

• Cochlear Implants: Convert sound into electrical signals for the auditory nerve.

• Hearing Aids: Amplify sound for better hearing.

3.6 Chemical Senses

Olfaction (Smell)

• Olfactory Epithelium: Membrane with receptor cells for smell.

• Olfactory Bulb: Where smell transduction occurs, signals sent to the amygdala and hippocampus.

• Olfactory Nerve: Carries smell signals to the brain.

Gustation (Taste)

• Taste Buds (Papillae): Structures on the tongue containing taste receptors.

• Five Basic Tastes: Sweet, salty, sour, bitter, savory (umami).

• Taste Pathway: Molecules stimulate taste buds, signals sent via the facial nerve to the thalamus and then to the temporal lobe.

3.7 Body Senses

Skin Layers

• Epidermis: Outer layer, protective barrier.

• Dermis: Middle layer, contains blood vessels and nerve endings.

• Hypodermis: Layer of fat insulating tissue and absorbing shock.

Pain and Proprioception

• Nociceptors: Sensory receptors detecting pain.

• Phantom Limb Sensations: Pain in lost body parts due to brain signals.

• Kinesthesis: Perception of body part position/movement.

• Proprioceptors: Sensory receptors in muscles/tendons helping perceive movement.

• Vestibular Sense: Balance maintained through shifting fluid in the inner ear.

Sensory Interaction

• Definition: Interaction between senses influencing perception.

  • Example: Flavor perception combining taste and smell.