Unit 5: Sensation and Perception
How raw energy from the world becomes a signal the brain can use, and how the brain assembles those signals into a scene.
13 topics · 47 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
5.1 Transduction and Absolute Thresholds
- How it worksHow does transduction convert physical energy like light or air pressure into a neural signal?
- Worked exampleFind why a candle flame is visible from 30 miles on a dark night but a lit match isn't detectable from that far.
- Common mistakeWhy isn't a stimulus below your absolute threshold completely undetectable in every situation?
Your turn1 of 2
A person can just barely detect the difference when 9 grams is added to a 129 gram weight. Using Weber's law, the just-noticeable difference is a constant fraction of the original stimulus, how many additional grams would need to be added to a 290 gram weight for the difference to be just as noticeable?5.1 Signal Detection Theory
- How it worksHow do signal detection theory's two overlapping distributions, noise and signal-plus-noise, decide what counts as a hit?
- How it worksWalk me through how sliding the decision criterion trades misses for false alarms.
- Worked exampleFind whether a radiologist set to a cautious criterion will produce more false alarms or more misses reading scans.
- Going furtherWhat happens to the criterion a person sets when the cost of missing a signal goes up sharply?
- Common mistakeWhy isn't a miss in signal detection theory simply a sign that someone wasn't paying attention?
Your turn1 of 2
In a signal detection experiment, a participant is presented with 88 trials in which a faint tone is actually played, and correctly detects it on 36 of them. What is the participant's hit rate, as a percentage?5.1 Sensory Adaptation
- How it worksHow does sensory adaptation reduce a receptor's response to an unchanging stimulus over time?
- Going furtherWhat happens to sensory adaptation the moment an unchanging stimulus suddenly changes?
- Common mistakeWhy doesn't sensory adaptation mean your sense organ has stopped working?
- Worked exampleFind why you feel your clothes touching your skin the moment you put them on but stop noticing within minutes.
Your turn1 of 2
After wearing a scented candle's fragrance for twenty minutes, someone stops noticing it at all, even though a visitor who just walked in immediately comments on how strong it smells. The person worries their sense of smell has stopped working. What is actually happening?5.2 Light and Sound as Waves
- How it worksHow do a wave's wavelength and amplitude translate into color and brightness for light, and pitch and loudness for sound?
- Worked exampleFind why a wavelength of about 700 nanometers looks red while about 450 nanometers looks blue.
- Going furtherWhat happens to a wave's perceived pitch when its frequency doubles?
Your turn1 of 2
A tone's frequency changes from 239 hertz to 1838 hertz. Using the number of octaves equal to the base-2 logarithm of the frequency ratio (log base 2 of f2 divided by f1, computed as ln(f2/f1) divided by ln(2)), how many octaves higher is the new tone?5.3 The Eye and Transduction in the Retina
- How it worksHow does light pass through the cornea and lens to focus an upside-down image onto the retina?
- How it worksWalk me through how rods and cones each transduce light differently in dim versus bright conditions.
- Going furtherWhat happens to color vision at night when only the rods, not the cones, are working well?
- Common mistakeWhy isn't the retina's blind spot, where the optic nerve exits, something you notice during everyday vision?
Your turn1 of 2
Walking from a bright parking lot into a dim movie theater, someone initially sees almost nothing, but gradually a grainy, colorless version of the room becomes visible after several minutes. What is happening during this adjustment?5.3 Color Vision Theories
- How it worksHow does the trichromatic theory explain color vision using just three types of cone?
- How it worksWalk me through how the opponent-process theory explains an afterimage that the trichromatic theory can't.
- Common mistakeWhy isn't color blindness usually a total inability to see any color at all?
Your turn1 of 2
One color vision theory explains normal color perception using three cone types, each most sensitive to red, green, or blue wavelengths. A different theory is needed to explain why staring at a green shape produces a red afterimage on a blank wall afterward. Which two theories are being contrasted, and which explains the afterimage?5.3 The Visual Pathway from Retina to Brain
- How it worksWalk me through the visual pathway from the retina through the optic nerve, the optic chiasm, and into the visual cortex.
- How it worksHow does the optic chiasm cross information so that each hemisphere sees the opposite half of the visual field?
- Worked exampleFind what field of vision is lost when a lesion sits on the optic nerve before the optic chiasm versus one on the optic tract after it.
- Going furtherWhat happens to a person's visual field when a stroke damages only their left visual cortex?
Your turn1 of 2
A lesion on the optic nerve before it reaches the optic chiasm causes total blindness in one eye. A different lesion, on the optic tract after the chiasm, instead causes loss of the same half of the visual field in both eyes. What explains this difference?5.4 The Ear and Transduction of Sound
- How it worksHow does sound travel from the eardrum through the tiny bones of the middle ear into the fluid-filled cochlea?
- How it worksWalk me through how hair cells in the cochlea transduce a vibration into a neural signal.
- Going furtherWhat happens to hearing when the hair cells in the cochlea are damaged instead of the eardrum?
- Common mistakeWhy isn't hearing loss from loud noise usually reversible the way a bruise eventually heals?
Your turn1 of 2
One patient has damage to their eardrum and the tiny middle-ear bones, while a different patient has damage specifically to the hair cells inside the cochlea. Both experience hearing loss. What is the key difference in what's actually broken?5.4 Theories of Pitch Perception
- How it worksHow does place theory explain pitch using where along the cochlea a sound wave peaks?
- How it worksWalk me through why frequency theory is needed to explain very low pitches that place theory can't account for.
- Worked exampleFind which pitch theory best explains detecting a deep bass note around 50 hertz.
Your turn1 of 2
A high-pitched sound causes maximum vibration at a very specific location near the base of the cochlea, while a lower-pitched sound peaks at a different location closer to its tip. Which pitch theory does this best describe, and how does it explain pitch?5.5 Taste and Smell as Chemical Senses
- How it worksHow do taste buds and olfactory receptors both detect chemicals instead of energy like light or sound?
- Common mistakeWhy isn't the tongue actually mapped into separate zones for sweet, sour, salty, and bitter?
- Going furtherWhat happens to flavor perception when smell and taste signals combine in the brain?
Your turn1 of 2
A textbook diagram from decades ago shows the tongue divided into separate zones exclusively for sweet, sour, salty, and bitter, with each taste only detectable in its own zone. What does more recent research say about this diagram?5.5 Touch, Pain, and Gate Control Theory
- How it worksHow does gate control theory explain pain signals getting blocked by other touch signals in the spinal cord?
- How it worksWalk me through how the body's own natural painkillers, endorphins, close the same pain gate.
- Going furtherWhat happens to pain perception in phantom limb syndrome, after the limb itself is gone?
- Worked exampleFind why an athlete can play through an injury during a game but feel the pain intensely once it ends.
Your turn1 of 2
Right after stubbing a toe, instinctively rubbing the area seems to genuinely reduce how much it hurts. According to gate control theory, why does this work?5.6 Gestalt Principles and Perceptual Constancies
- How it worksHow do the Gestalt principles of proximity, similarity, and closure group raw sensations into objects?
- How it worksWalk me through how size constancy keeps a person looking the same size as they walk away from you.
- Common mistakeWhy doesn't a plate viewed at an angle actually look elliptical to your perception the way it does in a photograph?
- Going furtherWhat happens to shape constancy when a door swings open and its image on your retina turns from a rectangle into a trapezoid?
Your turn1 of 2
A brand's logo is made of three separate dots arranged in a triangular pattern with no connecting lines at all, yet almost everyone who sees it perceives a complete triangle. Which Gestalt principle best explains this perception?5.6 Monocular and Binocular Depth Cues
- How it worksHow do monocular cues like relative size and linear perspective create depth with just one eye?
- How it worksWalk me through how binocular disparity between your two eyes' images creates a stronger sense of depth.
- Going furtherWhat happens to depth perception the moment you close one eye?
Your turn1 of 2
In a painting, two parallel roads appear to converge toward a single point near the horizon, creating a strong illusion of distance even though the painting itself is completely flat. Which monocular depth cue is being used here?