Domain: Healthcare — Human Physiology
Target concept: Pain response (burning sensation)

Video generation prompt: The subject gently placed a metal spoon heated in hot (but not boiling) water against the skin of the forearm for several seconds, then removed it.

Evaluation guide:
(i) Target concept: Non-damaging thermal nociception mediated by Aδ/C fibers resulting in immediate, transient protective motor and autonomic responses.
Minimum mechanism: The spoon must reach a temperature that activates thermosensitive nociceptors (roughly 43–45°C, clearly hot to the touch) while staying below the tissue-damage threshold (<45°C); enough heat must transfer into the epidermis/dermis on contact; the subject's neural circuitry must be intact to generate an observable protective micro-response without any injury.
(ii) Storyline: [Frame 0–2] Container of visibly hot water shown with the spoon submerged (steam or surface ripple visible) → [Frame 3–4] Spoon lifted out, its surface glistening with moisture → [Frame 5–6] Spoon carried toward the forearm in a smooth arc → [Frame 7–12] Full-surface contact established; forearm and/or facial micro-tensing begins at the same moment → [Frame 13–14] Spoon lifted away; micro-response ends immediately → [Frame 15] Spoon fully removed; no lingering reaction. All events occur from a fixed frontal/slightly oblique viewpoint; the contact zone stays fully visible; face and forearm remain in the same plane; no cutaways or perspective shifts.

Manual:
Experimental Procedure
1. Fill a small container with hot (but not scalding) water, roughly 43–45°C.
2. Submerge a metal spoon for ≥3 seconds.
3. Remove spoon, gently shake off excess water.
4. Place spoon flat against exposed forearm skin for several seconds.
5. Remove spoon cleanly.
Observation of Experimental Phenomena
During spoon contact: immediate, localized, transient tensing or micro-withdrawal of forearm muscles; subtle eye squint or lip tightening; no skin redness, blistering, or lasting change.
Summary of Experimental Principles
Activation of Aδ and C nociceptors by a brief, near-threshold heat stimulus triggers a protective withdrawal reflex and conscious burning sensation — a non-damaging pain response confirming intact peripheral nerve function.

Prompt Grounding rubric:
level_1: None of the required elements are visible: no metal spoon, no forearm skin, no contact between spoon and arm, and nothing in the scene (no container, no steam, no visible heating step) suggests the spoon was ever in hot water; the human subject is not identifiable, so the scene bears no visible relation to the described setup.
level_2: The metal spoon appears somewhere in the shot, but it is not being held toward the arm, or the forearm is shown without the spoon ever touching it; there is no container of water, steam, or wetness on the spoon to suggest a heating step; the sequence is missing at least two of the four expected stages: spoon approaching the arm, contact, a brief hold, and removal.
level_3: The spoon is held in a hand and visibly touches the forearm skin for a continuous stretch of time (no unexplained cuts or gaps in contact); the forearm is fully in view and anatomically correct, below the elbow; a hint of the heating step is present (the spoon looks damp or slightly reflective) even without a visible water container; the four stages (approach, contact, hold, removal) all occur, in the right order.
level_4: The spoon is held and makes clearly continuous contact with the forearm; the forearm is fully visible, unobstructed, at a natural angle; the heating step is visually supported: the spoon shows surface moisture or light condensation, and a small container of water with mild steam or ripples appears in the same scene shortly before contact; approach, contact, hold, and removal all occur in the correct order with nothing skipped or out of sequence.
level_5: The spoon is shown submerged in a small container of visibly hot water (gentle steam or surface ripples) before being lifted out still glistening with moisture, then carried in one smooth motion to make full, direct contact with bare forearm skin (no sleeve or cloth in the way); contact is held continuously for several seconds before the spoon is deliberately lifted away; the whole sequence plays out in one continuous shot with a fixed camera viewpoint, and the spoon's size relative to the hand and arm stays consistent throughout with no unnatural scaling.

Scientific and Causal Correctness rubric:
level_1: No sign of any pain-related response anywhere in the sequence: the forearm skin looks completely relaxed before, during, and after spoon contact, with no tensing, no withdrawal motion, and no facial reaction; in addition the spoon itself looks like it was never in hot water at all (fully dry, matte, room-temperature appearance), so nothing on screen suggests heat was involved.
level_2: Either the spoon shows some surface moisture or sheen consistent with having been in hot water, but the skin and face still show zero tensing, withdrawal, or expression change during contact; or, conversely, some body movement occurs (e.g., the arm shifts or the subject blinks) but it is clearly unrelated to the timing of contact (happening well before contact starts or well after the spoon is already removed), so it cannot be read as a pain response.
level_3: A localized muscle tensing or a small involuntary pull-away motion of the forearm appears during contact (e.g., a brief flex at the wrist or elbow), or the subject's face shows a brief squint or lip tightening; the response starts sometime during contact and fades out within about a second of the spoon being lifted away; no redness or lasting skin change appears.
level_4: The forearm shows a localized tensing or slight withdrawal, or the face shows a squint or lip-tightening, that starts only after the spoon has made contact and stops within roughly a second of removal, with no reaction visible before contact or lingering afterward; the spoon's surface shows a light, even sheen consistent with hot-water immersion (no dripping, no steam, no scald marks); nothing on screen (sweating, blistering, skin reddening) contradicts a mild, non-damaging heat exposure.
level_5: The forearm's tensing or withdrawal, and/or the facial squint or lip-tightening, begins right at the moment contact is made and ends right as the spoon lifts away, with no response visible at any other time in the sequence; the reaction is clearly visible to an observer (a real muscle flex or pull-away, not a hidden or ambiguous twitch); the spoon shows a uniform light sheen matching a hot (not boiling) water source; the overall timing of onset and offset lines up convincingly with a brief, non-damaging heat-triggered pain response.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the spoon appears already touching the forearm with no visible approach path, or the forearm itself disappears and reappears between frames; the contact point relocates to a different part of the arm without any motion in between; the spoon or hand changes size or shape implausibly from one frame to the next; the lighting on the scene shifts abruptly between frames with no visible cause; motion freezes or skips for more than three consecutive frames.
level_2: Moderate rupture: the spoon enters the frame from off-screen and reaches the skin with implausible sudden speed changes; the forearm rotates or shifts position with no matching movement of the hand or shoulder; the illumination on the arm and spoon switches from one side to the other within a single moment with no gradual change; the contact point slides across the skin surface in a way that skips positions rather than moving continuously.
level_3: Minor but noticeable discontinuity: the contact zone between spoon and skin is briefly hidden by a finger or the wrist for no more than one or two frames; the shadow cast by the spoon shifts slightly out of step with the spoon's own movement just before or after contact; the hand shows a small, visually noticeable jitter while holding still during the stillness phase; no full teleportation or disappearance occurs.
level_4: The spoon, hand, and forearm keep consistent relative sizes and positions throughout the sequence; the contact point stays on the same patch of forearm skin for the entire contact phase; the shadow cast by the spoon and hand moves smoothly in step with their motion; the arm, face, and spoon remain visible without being blocked at key moments (approach, contact, removal); motion looks smooth with no visible skipping or freezing.
level_5: The spoon's path from the water container to the forearm follows one continuous, physically plausible arc at a natural hand-movement speed; the contact patch stays visually fixed on the same spot of forearm skin across the entire contact and removal phases; the forearm, hand, and face hold a steady pose except for the permitted micro-response described in the science rubric; shadows and reflections on the spoon's metal surface shift smoothly and consistently with its motion and a single, unchanging light source; the whole motion sequence reads as one uninterrupted, natural movement with no stutters or abrupt jumps.