Sensation and Perception Principles

• Sensation is the detection of physical energy by sense receptors.
• Perception is the brain's interpretation of sensory data.
• Perceptual illusions occur when perception doesn't match physical reality.
• The Ebbinghaus-Titchener Illusion demonstrates the role of context in perception.
• The brain fills in missing visual information, activating the primary visual cortex (V1).

Principles of Sensation

• Transduction converts external stimuli into electrical activity within neurons.
• Sense receptors perform transduction.
• Müller's Doctrine of Specific Nerve Energies states that sensations are determined by the sense receptor, not the stimulus.
• Phosphenes are sensations of light caused by pressure on eye receptor cells.
• Sensory adaptation is the decrease in response to a stimulus over time.
• Psychophysics, studied by Gustav Fechner, examines how physical characteristics of stimuli relate to our perception.
• The absolute threshold is the lowest level of a stimulus needed for detection 50% of the time.
• The Just Noticeable Difference (JND) is the smallest detectable change in stimulus intensity.
• Weber’s Law: the JND is proportional to the original stimulus intensity.
• Stronger stimuli require higher JNDs, weaker stimuli require lower ones.
• Cross-modal processing influences perception.
• The McGurk Effect integrates visual and auditory information.
• Synesthesia involves cross-modal sensations, such as grapheme-color synesthesia.
• Lexical-taste synesthesia is a condition where words have associated tastes.

Attention in Sensation and Perception

• Selective attention is focusing on one sensory channel while minimizing others.
• The reticular activating system (RAS) is a network in the cerebral cortex involved in attention.
• In dichotic listening tasks, unattended messages are not well-processed.
• Treisman's "leaky filter" suggests unattended messages are processed to some degree based on meaning.
• Shadowing involves repeating the attended message.
• The cocktail party effect is when we become aware of relevant stimuli outside our attention.
• Inattentional blindness is the failure to notice stimuli in plain sight when attention is focused elsewhere.
• Change blindness is the failure to detect environmental changes.

The Visual System

• Light is electromagnetic energy, with humans sensitive to 400-700 nanometers.
• Brightness is the amount of light reflected.
• Hue is the color of light.
• The iris controls light entering the eye.
• The pupil is the opening where light enters.
• The pupillary reflex constricts the pupil in bright light.
• Pupil dilation occurs when processing complex information or during autonomic arousal.
• The cornea focuses light on the back of the eye.
• The lens adjusts shape (accommodation) to focus light on the retina.
• The retina is the membrane at the back of the eye.
• Cones are responsible for color vision and require high light levels.
• Rods are responsible for low-light vision and are absent in the fovea.
• Visual information travels from Optic Nerves > Optic Chasm > Optic Tract > Thalamus > Optic Radiations> Primary Visual Cortex (V1).
• Feature detectors are neurons in the visual cortex (V1) that respond best to specific stimuli.
• The trichromatic theory: color vision is based on sensitivity to blue, green, and red.
• The opponent process theory: color perception is based on opposing pairs: red vs. green, blue vs. yellow, black vs. white.

Other Senses

• Sound is vibration, with pitch determined by wave frequency (Hz) and loudness by amplitude (dB).
• Humans perceive frequencies from 20 to 20,000 Hz.
• The outer ear includes the pinna and ear canal.
• The middle ear contains ossicles that transmit sound to the inner ear.
• The cochlea in the inner ear converts vibration to neural activity, enabling pitch perception.
• The Organ of Corti and basilar membrane within the cochlea contain hair cells.
• Olfaction (smell) and gustation (taste) are "chemical senses”.
• Odors are airborne chemicals interacting with nasal passages.
• Humans can distinguish 2,000-4,000 different odors.
• The five basic tastes are sweet, salty, sour, bitter, and umami.
• Taste buds on the tongue contain receptors for each taste.
• The somatosensory system involves nerve endings in the skin (mechanoreceptors).
• This system responds to touch, pressure, temperature, and injury.
• Low-intensity touch stimuli result in slow neuron firing, while high-intensity stimuli result in fast firing.

Principles of Perception

• Bottom-up processing uses sensory data alone to construct a whole.
• Top-down processing modifies raw stimuli with experiences, knowledge, and expectations.
• Gestalt principles describe how we perceive objects as wholes.
• Proximity: Objects close together are perceived as unified.
• Similarity: Similar objects are seen as a whole.
• Continuity: Objects are perceived as whole even when blocked.
• Closure: Brains fill in missing parts of an image
• Symmetry: Symmetrically arranged objects are perceived as wholes.
• Figure-ground: Focus is on the central figure, ignoring the background.
• Motion perception involves comparing visual frames.
• The phi phenomenon is the illusion of movement from successive flashing lights.

Depth Perception

• Monocular depth cues rely on one eye.
• Relative size: Distant objects appear smaller.
• Texture gradient: Texture is less apparent farther away.
• Interposition: Closer objects block farther ones.
• Linear perspective: Outlines converge at a distance.
• Height in plane: Distant objects appear higher.
• Light and shadow: Shadows give 3-D form.
• Motion parallax: Nearby objects appear to move faster.
• Binocular depth cues require both eyes.
• Disparity: Eyes transmit different information for near objects.
• Convergence: Eyes focus inward for closer objects.
• The visual cliff experiment shows depth perception is partly innate and learned through experience.