Sensation and Perception

Transduction

Definition: The biological process of converting physical stimulus energy from the external environment into electrochemical neural impulses that the brain can interpret.

Example: Sensory receptors in the retina convert light waves into electrical signals sent along the optic nerve to the visual cortex

Psychophysics

Definition: The study of the relationship between physical energy/stimuli in the external environment and our psychological experience, sensation, and perception of those stimuli.

Example: Measuring the minimum volume (decibels) a person needs to hear a tone in a quiet room.

Absolute Threshold

Definition: The minimum intensity of a stimulus needed for a person to detect its presence 50% of the time.

Example: Seeing a candle flame flickering from 30 miles away on a pitch-black night or hearing a bird chirping softly outside your window.

Difference Threshold (Just Noticeable Difference - JND)

Definition: The smallest amount two stimuli must differ in intensity for a person to detect a noticeable difference between them.

Example: Feeling that a gym bag is heavier after adding a toy matchbox car or noticing your tea tastes sweeter after adding a second sugar cube.

Signal Detection Theory

Definition: Predicts how and when we detect a faint stimulus amid background stimulation; depends on personal experience, expectations, motivation, and fatigue.

Outcomes: Hit, Miss, False Alarm, Correct Rejection.

Example: A parent waking up instantly to a faint baby cry over a loud thunderstorm.

Weber's Law

Definition: To perceive a difference, two stimuli must differ by a constant minimum percentage rather than a fixed amount.

Example: Adding 1 oz to a 10 oz weight is easy to feel, but adding 1 oz to a 100 lb weight goes unnoticed.

Sensory Adaptation

Definition (PNS/Receptors): Receptors become less responsive to constant stimulus (e.g., getting used to cold pool water or clothes on your skin).

Sensory Interaction

Definition: One sense influences another (e.g., holding your nose makes food taste bland).

Selective Attention

Definition: Focusing conscious awareness on a single stimulus while filtering out others.

Example: Reading a textbook intently while ignoring background music/birds

Inattentional Blindness

Definition: Failing to see visible objects when attention is directed elsewhere (e.g., missing the gorilla passing through basketball players).

Wavelength (Light Wave Properties)

Definition (Distance between peaks): Determines Hue/Color (Short = Cool/Blue/Violet; Long = Warm/Red).

Rods

Definition: Night vision, dim light, motion/shapes, peripheral vision; located in outer retina.

Visual Pathway Through the Eye (Order of Structures)

1. Light Waves

   
   

   
   

2. Cornea

   
   

   
   

3. Pupil / Iris

   
   

   
   

4. Lens (Accommodation)

   
   

   
   

5. Retina (Rods & Cones)

   
   

   
   

6. Bipolar Cells

   
   

   
   

7. Ganglion Cells (Axons form Optic Nerve)

   
   

   
   

8. Optic Chiasm →→ Thalamus

   
   

   
   

9. Visual Cortex (Occipital Lobe)

Nearsightedness (Myopia)

Definition: Eyeball is too long; image focuses in front of retina; can't see far objects clearly.

Sensory Habituation

Definition (CNS/Brain): Brain stops paying attention to repeated stimuli (e.g., ignoring a ticking clock or air conditioner noise).

Synesthesia

Definition: Neurological condition where stimulation of one sense triggers an automatic experience in another (e.g., "hearing" colors or "tasting" words).

Cocktail Party Effect

Definition: Ability to focus on one voice in a noisy room, but instantly noticing when someone says your name.

Change Blindness

Definition: Failing to notice visible changes in the environment (e.g., failing to notice a speaker switch behind a desk).

Amplitude (Light Wave Properties)

Definition (Wave height): Determines Brightness/Intensity (Tall = Bright; Short = Dull)

Cones

Definition: Color vision, fine details; concentrated in the fovea; 3 types (Red, Green, Blue).

Farsightedness (Hyperopia)

Definition: Eyeball is too short; image focuses behind retina; can't see close objects clearly.

Place Theory

Pitch is determined by where the basilar membrane vibrates; best for high frequencies

Frequency Theory

Definition: Pitch is determined by the rate at which neural impulses travel up auditory nerve; best for low frequencies.

Volley Principle

Definition: Neurons fire in rapid succession/teams to handle frequencies above 1000 Hz.

Conduction Deafness

Definition: Damage to mechanical system conducting sound waves to cochlea (outer/middle ear: eardrum or ossicles).

Sensorineural Deafness

Sensorineural Deafness: Damage to hair cells/cochlea or auditory nerve (inner ear); caused by aging, loud noise, or genetics.

Prosopagnosia

Face blindness; inability to recognize familiar faces while retaining object recognition

Blind Spot

Area on retina where optic nerve leaves the eye; contains no photoreceptors.

Blindsight

Ability to respond to visual stimuli without consciously seeing them due to visual cortex damage.

Frequency (Pitch/Sound Wave Properties)

Measured in Hertz (Hz); higher frequency = higher pitch

Amplitude (Loudness/Sound Wave Properties)

Measured in Decibels (dB); larger wave height = louder sound.

Auditory Pathway (Path of Sound)

• Pinna (Outer Ear)

  
  

• Ear Canal →→ Eardrum (Tympanic Membrane)

  
  

  
  

• Middle Ear Ossicles (Hammer / Anvil / Stirrup)

  
  

  
  

• Oval Window of Cochlea

  
  

  
  

• Fluid moves Cilia (Hair Cells) on Basilar Membrane

  
  

  
  

• Auditory Nerve →→ Thalamus →→ Temporal Lobe (Auditory Cortex)

Olfaction (Smell) Pathway

Definition: Chemical sense detecting airborne odor molecules via olfactory nerve fibers/receptors in the nasal cavity's mucous membrane.

Brain Processing

Definition: Processes through the olfactory bulb, amygdala, and hippocampus — WITHOUT passing through the thalamus.

Example: Smelling perfume and instantly recalling a vivid childhood memory or feeling an emotional reaction.

Gustation (Taste)

Definition: Chemical sense processed by taste receptors on taste buds (papillae).

6 Basic Tastes: Sweet, Salty, Sour, Bitter, Umami (savory/meat), and Oleogustus (fatty).

Supertasters

Definition: Have a higher density/excess of papillae, making them overly sensitive to bitter foods and spices (often picky eaters).

Example: Someone who hates broccoli, dark chocolate, or coffee because they taste intensely bitter

Gate-Control Theory of Pain

Definition: Spinal cord contains a neural "gate" that either allows pain signals to pass to the brain or blocks them. Large nerve fibers (competing touch signals) can close the gate to reduce pain.

Example: Rubbing or scratching a bumped knee sends competing tactile signals that close the spinal gate, dulling the pain.

Kinesthetic Sense

Definition: Tracks body position and movement of individual body parts via receptors in muscles, tendons, and joints.

Example: Walking upstairs or clapping with eyes closed

Vestibular Sense

Definition: Tracks head position, balance, and gravity via semicircular canals and vestibular sacs in the inner ear

Example: Maintaining balance on a tightrope or feeling dizzy after spinning.

Phantom Limb Syndrome

Definition: Sensations or pain felt in a limb that has been amputated.

Cause: The brain's somatosensory cortex continues to receive/generate neural signals for the missing limb and misinterprets them as pain.

Example: An amputee feeling an itch or cramp in a arm/leg that is no longer there.

Sensation

Definition: Raw sensory data collected by receptors (eyes, ears, skin, tongue, nose).

Example: eyes receiving red light waves

Perception

Definition: How the brain organizes, interprets, and gives meaning to sensory information.

Example: Realizing that the red light wave is a “stop sign”

Bottom-Up Processing

Definition: Analysis that starts at entry-level sensory receptors and works up to the brain to build perception

Example: Assembling individual features of unfamiliar symbols to figure out a letter

Top-Down Processing

Definition: Information processing guided by higher-level mental processes, expectations, context, and past experiences (schemas).

Example: R34D1NG TH1S S3NT3NC3 because your brain fills in context.

Schemas

Mental frameworks shaped by cultural background/experience that organize how we interpret the world.

Perceptual Set

A mental predisposition or readiness to perceive one thing and not another based on expectations

Example: Expecting a drink to taste like fruit punch because the label is bright red, even if it's flavored water

Figure-Ground (Key Gestalt Principles of Perception)

Organizing visual field into objects (figures) that stand out from background (ground)

Proximity (Key Gestalt Principles of Perception)

Grouping nearby figures together.

Similarity (Key Gestalt Principles of Perception)

Grouping figures that look alike (similar shape/color)

Closure (Key Gestalt Principles of Perception$

Filling in gaps to create a complete, whole object.

Continuity (Key Gestalt Principles of Perception)

Perceiving smooth, continuous patterns rather than disrupted ones.

Relative Size: Monocular Depth Cues (Only One Eye Needed)

Smaller retina image = perceived as farther away.

Relative Clarity: Monocular Depth Cues (Only One Eye Needed)

Clearer = closer; blurry = farther.

Texture Gradient: Monocular Depth Cues (Only One Eye Needed)

Distinct, detailed textures = close; smooth/blended textures = far.

Linear Perspective: Monocular Depth Cues (Only One Eye Needed)

Parallel lines appear to converge in the distance (e.g., train tracks).

Interposition: Monocular Depth Cues (Only One Eye Needed)

An object blocking another is perceived as closer

Motion Parallax: Monocular Depth Cues (Only One Eye Needed)

Near objects appear to zip past quickly in the opposite direction; far objects move slowly in the same direction.

Convergence: Binocular Depth Cues (Both Eyes Needed)

Neuromuscular cue where eyes turn inward to focus on closer objects (eyes relax outward for far objects).

Retinal Disparity; Binocular Depth Cues (Both Eyes Needed)

Brain compares differing images from both eyes; larger discrepancy = closer the object.

Example: Holding your finger in front of your face and closing one eye at a time makes the finger "jump."

Visual Cliff Study

Definition: Lab device (table with a glass drop-off) used to test depth perception in infants and young animals.

Key Finding: Proved that infants can perceive depth and recognize potential danger early in life.

Perceptual Constancies

Definition: Perceiving objects as unchanging (size, shape, color, lightness) even as retinal images change.

Size Constancy: Knowing a approaching car isn't actually growing in size.

Shape Constancy: Knowing a door is still rectangular even when opened at an angle.

Color/Lightness Constancy: Knowing an object maintains its color/white shade despite changes in lighting or shadow

Stroboscopic Movement

Definition: Illusion of movement created when a rapid series of still pictures is shown in quick succession (e.g., flip books, movies)

Phi Phenomenon

Definition: Illusion of movement created when stationary lights blink on and off in rapid sequence (e.g., neon signs, holiday lights).

Dichromatism

Definition: A type of color vision deficiency involving having only 2 types of functional cone cells instead of 3.

Effect: Makes it very difficult to distinguish certain colors, most commonly red and green.

Opponent-Process Theory

Definition: Color is processed in opposing pairs: red-green, blue-yellow, and black-white.

Mechanism: When one color fatigues, its opposing color becomes more active.

Afterimages: An image seen on a neutral background after color receptors fatigue from opposing pairs.

Monochromatism

Definition: A rare total color blindness where an individual has only one type of cone cell or none at all.

Effect: Perceiving the entire world strictly in shades of gray.