Domain: Natural Science — Morphology
Target concept: Sexual dimorphism in the mallard duck: Males have iridescent green heads and chestnut-brown chests, while females have mottled brown plumage.

Video generation prompt: Two adult mallards (one female and one male) are displayed side by side in a fixed left/right arrangement, with each duck's sex identified either by a legible text label or by a stated positional convention (e.g., male on the left, female on the right). The video highlights the differences in the head, body, and tail regions of the two mallards.

Evaluation guide:
(i) Target concept: Visual demonstration of sexually dimorphic plumage in adult mallards as an evolutionary adaptation.
Minimum mechanism: Ducks must be taxonomically correct Anas platyrhynchos adults; the male's green head requires structural iridescence (not pigment-only green); the female's mottling requires stochastic brown-toned patterning (not solid or banded); tail curl is a rigid morphological trait, not a transient posture.
(ii)Storyline: Frame opens with a static side-by-side composition → each duck's sex is identified (via a legible label or the stated left/right convention) from the outset and stays unambiguous → viewer perceives head-region contrast first (iridescent green vs. mottled brown) → then chest region (solid chestnut-brown vs. mottled brown) → then tail region (curled vs. straighter) → all three contrasts stay simultaneously visible until the video ends; viewpoint is fixed (no pan/zoom), lighting is diffuse and frontal to avoid occlusion or glare; no duck movement distracts from the comparison.

Manual:
Experimental Procedure
1. Place two adult mallards (one male, one female) stationary and upright side-by-side in the same frame, in a fixed left/right arrangement.
2. Identify each duck's sex either with permanent, legible text labels ("Male"/"Female") next to the respective duck, or by consistently keeping the stated left/right convention (male on the left, female on the right) unambiguous throughout.
3. Maintain a fixed frontal or slightly angled viewpoint so the head, body, and tail regions of both ducks are visible at once.
Observation of Experimental Phenomena
- Male duck displays an iridescent green head, a rich chestnut-brown chest, and curled black-and-white tail feathers.
- Female duck displays cryptic mottled brown plumage across head, body, and tail, with no iridescence or uniform color patches.
- The visual contrast between sexes is immediately apparent in head color, chest hue, and tail shape.
Summary of Experimental Principles
Sexual dimorphism in Anas platyrhynchos: males exhibit ornamental, high-contrast plumage (iridescent green head, chestnut-brown chest) for mate attraction; females exhibit cryptic, low-contrast mottled-brown plumage for camouflage during nesting.

Prompt Grounding rubric:
level_1: No mallards appear, or only one duck appears, or the duck(s) shown are not adults, or there is no way at all (no label and no consistent position) to tell which duck is male and which is female.
level_2: Two adult mallards appear, but the sex identification is wrong or contradictory (e.g., a label mismatches the duck's plumage, or the stated left/right convention is violated partway through); or the two ducks are never shown together in the same side-by-side scene.
level_3: Two adult mallards appear side by side in the same scene; each duck's sex is correctly identifiable, either through a text label that matches its plumage or through a consistently maintained left/right position; however the head, body, and tail regions of the two ducks are not clearly separated for comparison: for example their bodies overlap, one is partly cropped out of frame, or the viewpoint is unstable enough to hide a region for long stretches.
level_4: Two adult mallards appear side by side, correctly sex-identified throughout (by label or by a fixed left/right position); the head, body, and tail regions of both ducks stay visible and comparable for the entire video; neither duck is occluded, cropped out of frame, or turned away from the camera for an extended stretch.
level_5: Two adult mallards appear side by side, correctly sex-identified throughout; the head, body, and tail regions of both ducks are fully visible in a stable, comparable framing for the whole video, shown in an unobstructed frontal or three-quarter posture; if text labels are used, they stay legible, stay next to the correct duck, and never detach, drift away, or swap ducks.

Scientific and Causal Correctness rubric:
level_1: The male duck's head looks brown or mottled instead of iridescent green, or the female duck shows green or vividly bright coloring instead of mottled brown, or both ducks show identical plumage, or no sex-specific coloring appears at all.
level_2: The male duck has a green head but its chest is not a warm chestnut-brown (e.g., it looks grey, black, or an unnatural color like purple or blue); or the female duck's mottled brown plumage is broken up by patches of green or bright color; or the combination of head, chest, and tail is biologically inconsistent (e.g., a male with a brown head and a chestnut chest but no green anywhere).
level_3: The male duck shows an iridescent green head and a chestnut-brown chest; the female duck shows mottled brown plumage; both are recognizable adult mallards; however the tail region is missing the male's curled feathers or the female's straighter tail (or the two tails are not visually distinguished), or one region's pattern is wrong: for instance the female's chest is rendered as a flat, unmottled brown block instead of a speckled pattern.
level_4: The male duck shows an iridescent green head, a chestnut-brown chest, and curled tail feathers; the female duck shows mottled brown plumage across head, body, and tail; all three regions on both ducks match real mallard coloring and pattern, with no swapped or invented traits.
level_5: The male duck shows the full set of breeding-plumage traits: an iridescent green head, a solid chestnut-brown chest, and tightly curled dark tail feathers; the female duck shows the full set of cryptic traits: mottled brown speckling across head, body, and tail with no iridescent sheen and no solid color patches; every one of these traits stays visible and consistent, never blurring into a different color or pattern, for the full duration of the video.

Spatiotemporal Consistency rubric:
level_1: One of the ducks vanishes from the frame or reappears somewhere else in the shot; a label detaches and jumps to a new position; the lighting flickers hard enough to break the sense of continuous time; a duck's head or body visibly stretches, twists unnaturally, or splits apart.
level_2: One duck shifts sideways by more than half its own body width between frames with no walking motion to explain it; a label's position visibly drifts across the video; the lighting swings between fully shadowed and fully bright with no gradual change; the motion looks jerky, with three or more visible frame skips.
level_3: The two ducks stay in the same left-right arrangement relative to each other; any labels stay attached to their duck; the lighting stays about the same brightness and direction from start to finish; neither duck's body distorts or breaks apart; any motion, such as a small head turn, is slow and looks natural.
level_4: The two ducks keep the same relative left-right spacing throughout, with no sliding or repositioning; any labels stay next to the correct duck without shifting or blurring; the lighting and the shadows the ducks cast keep the same direction and brightness for the whole clip; small motions, like feather settling or a slight head tilt, look smooth rather than stepped or glitchy.
level_5: The two ducks occupy the same relative positions in every frame with no drift; any labels stay sharply readable and correctly placed next to their duck for the entire video; the lighting, shadow direction, and viewing angle stay fully consistent from the first frame to the last; small motions like an eye blink or a feather ruffle look independent between the two ducks and physically plausible; there is no flicker, no ghost trailing, and no frame where a duck briefly doubles or smears.