Domain: Healthcare — Human Physiology
Target concept: Pupillary Light Reflex (Dim Light)

Video generation prompt: A person faces forward. The room lighting is dimmed. The lens focuses on one eye. Throughout the change in lighting conditions, the eye remains open. Smooth light variation and stable eye position are demonstrated.

Evaluation guide:
(i) Target concept: Pupillary light reflex under dim-light stimulation
Minimum mechanism: Intact afferent pathway (retina → pretectal nucleus) signaling reduced luminance, a parasympathetic efferent pathway (Edinger-Westphal nucleus → ciliary ganglion → iris sphincter) whose tone is withdrawn in dim light, and a separate sympathetic efferent pathway (hypothalamus → spinal cord T1-T2 → superior cervical ganglion → iris dilator) that activates to contract the dilator muscle; functional photoreceptor adaptation; absence of pharmacologic or neurologic blockade.
(ii)Storyline: [Phase 1: Baseline] Forward-facing subject, eye open and centered, ambient light at moderate level, pupil at resting size. [Phase 2: Transition] Lighting begins smooth dimming; eye remains static and open; no pupil response yet. [Phase 3: Response Onset] As illumination decreases, pupil starts widening, first at margins, then uniformly. [Phase 4: Stabilization] Dim light reaches steady state; pupil achieves new larger diameter and holds. [Perspective constraint] Fixed frontal macro-view of single eye only; no head, hands, or instruments visible; no change in viewpoint, focus, or framing. [Visibility constraint] Pupil, iris, sclera, and corneal reflection must remain fully discernible and anatomically coherent throughout: no occlusion, blur, or rendering failure.

Manual:
Experimental Procedure
1. Person sits facing camera, head stabilized.
2. Camera frames a tight, steady close-up on one open eye.
3. Ambient room lighting smoothly transitions from baseline to dim.
Observation of Experimental Phenomena
Pupil diameter increases continuously and exclusively during the dimming phase; eye remains open and motionless; no blinking, squinting, or gaze shift occurs.
Summary of Experimental Principles
In dim light, retinal photoreceptors signal reduced photon capture → parasympathetic inhibition + sympathetic activation → iris sphincter relaxation + dilator muscle contraction → pupil dilation (mydriasis) to maximize light entry.

Prompt Grounding rubric:
level_1: No human face or eye is visible in frame; the ambient room lighting never dims from its baseline level; the subject is not facing forward; or no continuous frontal close-up of a single eye is ever established.
level_2: A forward-facing face is present, but the eye is not held in a steady, isolated close-up; OR the room lighting changes but without a clear, continuous dimming sequence; OR the eye closes, blinks, or squints during the lighting change; OR the camera position, distance, or angle shifts mid-sequence.
level_3: A forward-facing person is shown; one eye is centrally framed in a steady macro close-up and stays in focus throughout; ambient room lighting visibly and continuously transitions from a brighter baseline to a dimmer state; the eye stays open and the head remains stationary; no hands, instruments, or other body parts enter the frame.
level_4: All 3-point conditions are satisfied AND the lighting transition from bright to dim is smooth, with no abrupt jumps, flickers, or re-brightening partway through; the framing, focus distance, and camera angle on the eye stay fixed with no detectable shift, tilt, or drift; no extraneous motion (eyelid flutter, brow movement, head micro-motion) distracts from the eye and the lighting change.
level_5: All 4-point conditions are satisfied AND the single continuous dim-light transition starts only after the eye is fully visible, open, and centered in frame, runs without interruption until the dimmer ambient level is reached and held steady, and the frontal single-eye framing, focus, and camera distance at the final held-dim moment match those established at the opening baseline moment.

Scientific and Causal Correctness rubric:
level_1: Pupil size shows no change despite the lighting dimming; OR the pupil constricts (gets smaller) as the light dims; OR the pupil dilates while the light is getting brighter; OR no pupil is visible at all; OR more than one pupil or an obviously artificial/painted eye is shown.
level_2: The pupil is visible and its size changes, but in the wrong direction for dim light (e.g., it constricts instead of dilates); OR the size change happens without any lighting change; OR the change is discontinuous (sudden jumps, resets, or oscillation back and forth); OR the pupil looks non-biological (flat black disc, hard geometric edge, unnatural rim).
level_3: The pupil is clearly visible within the iris; its diameter increases as the room dims; the size change goes only one direction (no constriction or pause partway through); the increase occurs only while the lighting is transitioning to the dimmer state, with no dilation occurring before the dimming begins.
level_4: All 3-point conditions are satisfied AND the pupil's dilation is continuous, with no stutter, freeze, or stepwise jump in size; the dilation begins after the dimming starts and finishes after the dimming stabilizes; iris texture, scleral whiteness, and the corneal light reflection stay consistent and anatomically plausible for a human eye throughout.
level_5: All 4-point conditions are satisfied AND the dilation's pace visually resembles the real pupillary reflex: a gradual expansion that is not a constant-speed linear ramp and shows no overshoot past the final size or visible tremor; the pupil remains visibly circular and centered within the iris while its diameter grows, with no flattening, elongation, or other distortion of its rim; no artifact-induced break in the pupil boundary or iris pattern appears at any point.

Spatiotemporal Consistency rubric:
level_1: The eye disappears and reappears, or the camera cuts/jumps to a different shot; the ambient light flashes or strobes rather than dimming smoothly; the eye rotates or drifts out of frame; the pupil's outline warps, tears, or fractures between frames; a shadow appears or shifts abruptly across the eye in a way unrelated to the lighting dim.
level_2: Minor but repeated instability across frames: slight jitter in the eye's position; the image intermittently loses sharpness; the corneal highlight's location hops inconsistently; ambient shadows on the face flicker; the pupil's edge visibly shimmers or breaks up between frames.
level_3: The eye stays fully visible and centered in the frame; the ambient lighting dims smoothly, with no visible flicker or sudden blotchy brightness steps across the sclera or iris; there is no object teleportation or structural warping of the eye; no visible cuts or dissolves interrupt the shot; the corneal highlight moves coherently with the implied lighting change; no abrupt brightness or contrast jump occurs that is unrelated to the dimming.
level_4: All 3-point conditions are satisfied AND the pupil's growth in size looks fluid rather than stepped: no visibly stuttering or stroboscopic jumps in dilation, and no obviously missing in-between pupil sizes; the iris, pupil, and sclera keep a consistent visual relationship with no apparent shifting of one relative to another; the eye's outline and eyelid margin stay aligned frame to frame with no visible misalignment.
level_5: All 4-point conditions are satisfied AND the pupil center, iris boundary, limbus, and eyelid margins show no visible drift, jump, or repositioning relative to one another across the entire sequence; the lighting change appears uniform across the sclera and iris, with no localized bright hotspots or dark voids appearing or moving independently; there is no visible ghosting, smearing, or motion blur inconsistent with an eye that is otherwise held still.