Test review

Sensation and Perception

• Sensation:

  • Stimulation of sense organs; raw sensory information.

• Perception:

  • Selection, organization, and interpretation of sensory input into conscious experience.

Processing Types

• Bottom-Up Processing:

  • Sensory input is processed feature by feature to build a perception.

• Top-Down Processing:

  • Perception is influenced by expectations, knowledge, and context.

Transduction

• Definition: The process of converting sensory stimuli into neural signals for interpretation by the brain.

• Importance: Necessary because the brain only understands neural signals, not raw sensory input.

Thresholds in Sensory Processing

• Absolute Threshold:

  • Minimum intensity required for a stimulus to be detected 50% of the time.

• Difference Threshold (Just Noticeable Difference, JND):

  • The smallest difference between two stimuli that is detectable.

• Weber’s Law:

  • The JND is a constant proportion of the original stimulus intensity.

Signal Detection Theory

• Concept: Perception depends on stimulus sensitivity and decision-making.

  • Hits: Correctly detecting a stimulus.

  • Misses: Failing to detect a present stimulus.

  • False Alarms: Detecting a stimulus that isn’t there.

  • Correct Rejections: Not detecting an absent stimulus.

• Sensory Adaptation:

  • Diminished sensitivity to constant stimulation.

Structure of the Eye

• Key Components:

  • Rods and Cones: Photoreceptors for light.

  • Retina: Contains photoreceptors and processes visual information.

  • Cornea: Transparent front part aiding in focus.

  • Pupil: Adjustable opening for light entry.

  • Iris: Colored part regulating pupil size.

  • Lens: Focuses light onto the retina.

  • Optic Nerve: Transmits visual information to the brain.

  • Fovea: Area of sharpest vision.

  • Blind Spot: Area without visual receptors.

  • Optic Chiasm: Where optic nerves cross.

Visual Processing in the Brain

• Ganglion Cells:

  • Send visual information to the brain.

• Dorsal Stream:

  • Processes spatial location ("Where").

• Ventral Stream:

  • Processes object recognition ("What").

Theories of Color Vision

• Trichromatic Theory:

  • Three cone types (red, green, blue) mix to form all colors.

• Opponent Process Theory:

  • Colors are perceived in opposing pairs (red-green, blue-yellow, black-white).

Gestalt Principles of Perception

• Figure-Ground: Distinguishing objects from their background.

• Proximity: Objects near each other are grouped together.

• Closure: Filling in gaps to perceive complete objects.

• Illusory Contours: Seeing edges even when not present.

• Similarity: Grouping similar-looking objects.

• Simplicity: Preference for simplest organization.

• Continuity: Seeing continuous patterns rather than abrupt changes.

• Common Fate: Elements moving together are perceived as a group.

Face Perception

• Highly specialized brain function for recognizing faces.

• Thatcher Illusion: Inverted faces distort the detection of facial features.

Depth Perception Cues

• Binocular Cues: (Two Eyes)

  • Retinal Disparity: Greater differences between images seen by each eye for closer objects.

  • Convergence: Eyes turn inward to focus on close objects.

• Monocular Cues: (One Eye)

  • Linear Perspective: Parallel lines converge in the distance.

  • Texture Gradient: Closer objects have more detail.

  • Occlusion: Closer objects block farther ones.

  • Relative Size: Larger objects appear closer.

  • Light & Shadow: Shadows provide depth cues.

  • Motion Parallax: Closer objects move faster relative to us.

Perceptual Constancies and Illusions

• Shape Constancy: Objects maintain shape despite angle changes.

• Size Constancy: Objects maintain size despite distance changes.

• Classic Illusions:

  • Ames Room: Distorted room creates size illusions.

  • Ponzo Illusion: Same-sized objects appear different in size due to background lines.

  • Motion Perception: Distortion in perceived speed based on movement.

Structure of the Ear and Sound Processing

• Outer Ear: Collects sound waves.

• Middle Ear: Contains eardrum and ossicles (hammer, anvil, stirrup); amplifies vibrations.

• Inner Ear:

  • Cochlea: Fluid-filled structure where sound is transduced by hair cells.

  • Basilar Membrane: Vibrations moving hair cells send signals to auditory nerve.

• Auditory Pathway: Cochlea → Auditory nerve → Thalamus → Auditory cortex.

• Place Coding: High frequencies encoded by hair cell location.

• Temporal Coding: Low frequencies encoded by neuron firing rates.

• Cochlear Implants: Bypass damaged hair cells by directly stimulating the auditory nerve.

Smell and Taste Mechanisms

• Smell (Olfaction):

  • Odorants activate receptors in the olfactory epithelium.

  • Signals travel to the olfactory bulb, then to the prefrontal cortex (pleasantness) and memory/emotion areas.

  • Pheromones: Chemicals triggering behavioral responses.

• Taste (Gustation):

  • Taste buds detect flavors.

  • Five basic tastes: Sweet, sour, salty, bitter, umami.

  • Supertasters: More taste buds leading to more intense flavor experiences.

Touch and Pain Perception

• Touch: Detected through skin receptors (pressure, temperature, pain).

• Pain Pathways:

  • Fast Fibers: Sharp, immediate pain (physical pressure, extreme temperature).

  • Slow Fibers: Chronic, dull pain (tissue damage).

• Gate-Control Theory of Pain: Spinal cord