Sensation and Perception Distinctions

Sensation vs. Perception

• Sensation. Raw detection. A rod fires when photons hit it.
• Perception. Interpretation. “That’s my grandmother’s face.”

Key distinction: sensation = receptor-level. Perception = brain-level. If the passage says “detected” or “registered,” think sensation. If it says “recognized” or “identified,” think perception.

Absolute Threshold vs. Just Noticeable Difference (JND)

• Absolute threshold. Minimum intensity to detect a stimulus 50% of the time. “Can I hear the phone at all?”
• JND (difference threshold). Minimum CHANGE in a stimulus that’s detectable 50% of the time. “Is the phone getting louder?”

Key distinction: absolute threshold compares to nothing (silence). JND compares to an already-present stimulus.

Sensory Adaptation vs. Habituation

• Sensory adaptation. Receptor-level. The receptor literally stops firing. Your nose stops smelling your perfume after an hour.
• Habituation. Brain-level. The receptor still fires, but the brain filters the signal. You stop consciously hearing the AC unit hum.

Key distinction: adaptation = receptor fatigue. Habituation = CNS-level dismissal. Both reduce response, but for different biological reasons.

Transduction vs. Transmission

• Transduction. Converting physical energy into a neural signal. Light → electrical impulse in a rod.
• Transmission. Passing that neural signal along to other neurons.

Key distinction: transduction happens at the receptor (one step). Transmission happens between neurons (the relay).

Top-Down vs. Bottom-Up Processing

• Bottom-up. Data-driven. Start with raw sensory input, build up to recognition. A baby seeing a new object.
• Top-down. Expectation-driven. Start with what you expect to see, use it to interpret ambiguous input. “Where’s Waldo?”

Key distinction: bottom-up = no prior knowledge required. Top-down = uses prior knowledge to fill gaps (and can create illusions).

Trichromatic Theory vs. Opponent-Process Theory

• Trichromatic (Young-Helmholtz). Three cone types (red, green, blue). Any color = a mix. Explains TV screens.
• Opponent-process (Hering). Three opposing pairs (red-green, blue-yellow, black-white). Explains afterimages (stare at green → see red afterimage).

Key distinction: trichromatic operates at cones (retina). Opponent-process operates downstream (ganglion cells onward). Both are right at different stages.

Place Theory vs. Frequency Theory (Hearing)

• Place theory. Different frequencies stimulate different LOCATIONS on the basilar membrane. Best for high frequencies (>2000 Hz).
• Frequency theory. Neurons fire at the same rate as the incoming sound wave. Best for low frequencies.

Key distinction: place = which spot on the cochlea. Frequency = how fast the neurons fire. Both work together in the middle range.

Conductive vs. Sensorineural Hearing Loss

• Conductive. Problem in the PATH of sound (wax, torn eardrum, fused ossicles). Patient hears their own voice normally (bone conduction) but struggles with external sound.
• Sensorineural. Damage to HAIR CELLS or the auditory nerve. All sounds affected. Cochlear implants bypass dead hair cells.

Key distinction: conductive = mechanical blockage. Sensorineural = neural damage. If the passage says “loud concerts” or “aging,” think sensorineural.

Proprioception vs. Kinesthesia

• Proprioception. Knowing where your body PARTS are in space right now. Touching your nose with eyes closed.
• Kinesthesia. Knowing how your body is MOVING. Adjusting mid-step after tripping.

Key distinction: proprioception = static position (cognitive). Kinesthesia = active motion (behavioral). Close, but proprioception is about “where” and kinesthesia is about “how I’m moving.”

Pharmacology of Pain: Nociception vs. Thermoreception

• Nociception. Pain detection. C fibers (slow, dull) and A-delta fibers (fast, sharp).
• Thermoreception. Temperature detection. TrpV1 receptors (also detect capsaicin = why chili feels hot).

Key distinction: pain vs. temperature. TrpV1 blurs them - fires on heat OR capsaicin OR noxious pain. That’s why spicy food feels hot.

Labeled Line vs. Shape (Steric) Theory of Olfaction

• Labeled line. Each odor receptor is “labeled” for a specific smell. One line = one odor.
• Shape (steric) theory. Odor molecules fit receptors by MOLECULAR SHAPE, like a lock and key.

Key distinction: labeled-line = specific receptor-per-smell. Shape = lock-and-key fit. Shape theory is the modern dominant view.

Signal Detection: Sensitivity (d’) vs. Response Bias (c)

• d’ (sensitivity). How well you can tell signal from noise. A property of the stimulus/detector.
• c (response bias). Your strategy. Conservative = “I only say yes when sure.” Liberal = “I say yes often.”

Key distinction: d’ is about HOW WELL the person discriminates. c is about the strategy they choose. Two subjects can have the same d’ but opposite c.