Domain: Healthcare — Skin Physiology
Target concept: Dermatographism (Delayed Type)

Video generation prompt: Demonstrate delayed dermographism. Select the forearm of a healthy adult for the procedure. Use a blunt stick to draw a straight line on the skin with moderate pressure. After an interval representing the multi-hour delay characteristic of this reaction (shown here in compressed form), re-examine the marked area. Clearly demonstrate the entire procedure step by step.

Evaluation guide:
(i) Target concept: Delayed dermographism as a mast-cell–mediated cutaneous hypersensitivity response to mechanical trauma.
Minimum mechanism: Mechanical pressure must trigger delayed (not immediate) histamine release causing localized capillary leak and dermal edema, requiring intact mast cells, functional histamine receptors, and normal vascular permeability; absence of concurrent urticaria or systemic illness.
(ii)Storyline: Phase 1 (Baseline): Static shot of healthy volar forearm under diffuse lighting: skin smooth, uniform pink-red tone, no lesions. Phase 2 (Stimulation): Blunt stick enters frame, contacts skin, and draws straight line with visible transient blanching/indentation, no wheal. Phase 3 (Latency): Absolute stillness, same frame, same lighting, no skin change. Phase 4 (Reaction): At re-examination onset, linear wheal emerges *de novo* along drawn path: continuous, elevated, homogeneously pink-red, coextensive with line, no spread beyond margins. Visibility constraints: Fixed frontal view; no occlusion; full focus on skin surface; lighting reveals subtle elevation and color contrast against baseline.

Manual:
Experimental Procedure
1. Position volar forearm of healthy adult in stable, well-lit view.
2. Use blunt, rounded-tip stick to draw one straight line on skin with moderate pressure.
3. Pause — this stands in for the multi-hour real-world latency period; maintain visible stillness for the shown interval.
4. Re-examine the exact same skin location.
Observation of Experimental Phenomena
A delayed, linear, raised, pink-to-red wheal appears exclusively along the path of the prior line during re-examination — absent during drawing and pause.
Summary of Experimental Principles
Delayed dermographism is a variant of skin hypersensitivity in which mechanical stimulation triggers mast cell degranulation only after a lag period — classically 3–8 hours, with wheals that can persist up to 48 hours — resulting in localized histamine-mediated wheal formation along the line of pressure. This is distinct from immediate (simple) dermographism, in which the wheal appears within minutes of stimulation.

Prompt Grounding rubric:
level_1: No forearm is shown; no blunt stick appears; no straight line is drawn on skin; no re-examination shot occurs: none of the three required steps (drawing, pause, re-examination) is present.
level_2: The forearm is visible and correctly oriented, but at least two of the three required steps are missing or wrong: e.g., the tool used is a pointed object (needle, fingernail, stylus) instead of a blunt stick, or no linear drawing motion is shown (just pressing), or the re-examination shot is missing entirely.
level_3: All three steps appear in order: (1) a blunt stick contacts the forearm and moves in a line to draw a straight mark, (2) a visible pause follows with no further marking, (3) the camera returns to the forearm to show the marked area; but at least one execution flaw remains: the line is visibly not straight, or the re-examination view is clearly a different patch of skin than where the line was drawn, or the stick's tip looks pointed rather than blunt.
level_4: All three steps appear in correct order and are spatially faithful: a stick with a clearly rounded, non-pointed tip draws one continuous straight line on the forearm; an unbroken pause follows with no drawing motion or camera movement; the re-examination shot shows the same patch of skin, same orientation, same framing; but one visual detail is off: the drawing shows no visible skin indentation/blanching from pressure, or the re-examination shot is soft-focus, partly blocked, or reframed compared to the drawing shot.
level_5: All three steps appear in correct order with full visual fidelity: a stick with an unmistakably rounded, blunt tip presses firmly against the forearm and draws a single straight line, with visible transient blanching or indentation where it presses; an uninterrupted pause follows with no movement of tool, hand, or camera; the re-examination shot returns to the exact same skin location with matching framing, focus, and orientation as the drawing shot, with no pan, zoom, or rotation.

Scientific and Causal Correctness rubric:
level_1: No skin reaction is ever shown: the skin looks the same before, during, and after marking, with no wheal at any point; or a wheal appears instantly as the stick is lifted (no delay at all), which contradicts a delayed reaction.
level_2: A skin change appears, but it contradicts delayed dermographism: e.g., a wheal or flare appears while the line is still being drawn (not delayed), or redness spreads outward during the drawing itself, or swelling appears with no line ever having been drawn, or the reaction shows up on a different part of the arm than where the line was made.
level_3: A raised change appears only once the re-examination shot begins, following the path of the earlier line; but at least one flaw remains: the wheal begins to appear before or exactly as the re-examination starts rather than clearly after the pause, or the wheal has visible breaks/gaps along its length rather than running continuously, or it is curved/branched rather than following the straight line, or its color is off (e.g., pale, purplish, or yellowish instead of pink-to-red).
level_4: A delayed, raised wheal appears only during the re-examination shot, following the exact path of the earlier line, continuous and straight, pink-to-red in color; but one detail is missing: no visible blanching or indentation was shown while the line was being drawn, or the wheal's height looks uneven along its length (flatter in places), or something in the background (a mark, hair, or lighting flare) partly obscures the wheal.
level_5: The delayed wheal appears only during the re-examination shot (not before or during drawing or the pause), runs continuously along the full length of the drawn line with even height and a straight path, shows a uniform pink-to-red color with no pale, blue, or dark patches, and sits on skin that otherwise looks the same as at the start, with nothing else in the frame competing for attention and no ambiguity about when it appeared relative to the re-examination.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the forearm disappears and reappears, or is in a completely different position/orientation between phases; the stick appears or disappears without ever being carried into or out of frame; the line appears fully formed with no visible drawing motion; the lighting or shadow direction on the arm changes abruptly between phases (e.g., daylight shifting to tungsten light, or the shadow suddenly flipping direction); the camera view jumps to an unrelated angle or distance between the drawing and re-examination shots; or the video visibly freezes or skips more than once.
level_2: Moderate rupture: the forearm remains visible but clearly shifts to a different position or angle in the frame between the drawing and re-examination shots; or the stick changes hand, grip, or shape between contact and the pause; or the drawn line's location on the skin visibly moves between phases; or the re-examination shot shows a different patch of forearm (different hair pattern, mole, or skin texture) than where the line was actually drawn.
level_3: The forearm, stick, and line all stay clearly in the same place and orientation across phases, but one visually noticeable inconsistency remains: the brightness or direction of light/shadow on the arm changes noticeably between the drawing and re-examination shots, or the camera framing/zoom is visibly different (clear crop change) between phases, or there is one brief, visible stutter during the pause; but there is no relocation of the forearm or stick, no tool appearing/disappearing, and the drawing-pause-re-examination order is preserved.
level_4: The forearm stays in the identical position, scale, and orientation in every shot; the stick is held in the same hand with the same grip throughout its appearances; the line is drawn in one continuous, visible motion; the pause shows no visible movement of forearm, stick, or camera; the lighting and shadow on the arm look the same across the drawing and re-examination shots; but one clearly visible discrepancy remains, such as a moment where the hand's motion looks unnaturally fast or blurred for the drawing speed, or a highlight/reflection on the skin shifts position without any corresponding change in the light source.
level_5: The forearm's position, angle, and framing are identical in the drawing and re-examination shots; the stick is held with the same grip and approaches the skin at the same angle every time it appears; the line is drawn in a single smooth, continuous motion with no jump cuts; the pause shows the forearm and stick completely motionless with the camera locked in place; the re-examination shot returns to frame the same patch of skin with the same lighting, shadow direction, and camera distance as the drawing shot, with no visible jump, shift, or change in any of these between phases.