Domain: Humanities and Social Sciences — Linguistics
Target concept: During vowel articulation, the airflow causes a thin strip of paper to move continuously and steadily.

Video generation prompt: A person places a thin tissue in front of the mouth, sustains an open vowel, briefly switches to a stop consonant, and then returns to the original vowel.

Evaluation guide:
(i) Target concept: Aerodynamic coupling between vocal tract airflow and lightweight suspended tissue during speech articulation.
Minimum mechanism: Continuous laminar oral airflow during vowels generates sufficient steady Bernoulli pressure differential to displace tissue outward; complete oral occlusion during stops eliminates airflow and pressure gradient, resulting in immediate tissue stillness.
(ii)Storyline: [Phase 1] Tissue placed statically in front of mouth → [Phase 2] Vowel onset triggers immediate outward tissue displacement → [Phase 3] Stop consonant onset causes instantaneous cessation of motion → [Phase 4] Vowel return triggers immediate resumption of identical outward motion → All phases observed from fixed frontal viewpoint with tissue and mouth fully visible and co-aligned; no occlusion, no repositioning, no external interference.

Manual:
Experimental Procedure
1. Person holds a thin, off-white tissue sheet in front of mouth, centered horizontally and level with oral opening.
2. Person sustains an open vowel (e.g., /a/) for ~2 seconds while keeping tissue stationary in place.
3. Person briefly articulates a stop consonant (e.g., /p/) — full oral closure followed by release — with no tissue repositioning.
4. Person immediately returns to the same open vowel for ~2 seconds.
Observation of Experimental Phenomena
Tissue moves continuously and steadily outward during both vowel phases; motion stops completely during stop consonant articulation; motion resumes identically upon vowel return.
Summary of Experimental Principles
During vowel articulation, vocal tract is open and airflow is continuous, causing aerodynamic pressure that displaces lightweight tissue outward. During stop consonants, airflow is fully blocked, eliminating pressure differential and halting tissue motion.

Prompt Grounding rubric:
level_1: No person is shown, no thin tissue appears in front of a mouth, no mouth is visible, and no vowel-to-stop-consonant-to-vowel speech sequence is attempted.
level_2: A person and their mouth are visible, but no tissue is held in front of the mouth, or the tissue is present while the speech sequence never actually includes both a sustained open vowel and a stop consonant.
level_3: A person holds a thin strip of tissue directly in front of an open mouth; the mouth visibly sustains an open-vowel shape (jaw dropped, lips parted, as for an 'ah' sound); the person then visibly switches to a stop consonant with a clearly visible articulatory closure (for example, lips pressed together for /p/ or /b/, or visible tongue-tip contact for /t/ or /d/); the mouth then returns to the same open-vowel shape -- all three phases occur in this order.
level_4: All of score 3, and the tissue stays in essentially the same position in front of the mouth for the entire clip (it is not dropped, replaced, or visibly repositioned by a hand mid-sequence); the mouth stays fully visible and roughly centered in frame throughout; and no unrelated action (a hand adjusting the tissue, the person turning away, a mid-clip cut) interrupts any of the three phases.
level_5: All of score 4, and the tissue hangs directly in the exhaled airstream -- centered on the mouth opening with its lower edge near lip level -- with nothing else blocking the view of either the tissue or the mouth; the person's head stays still enough that the framing barely changes; and the clip plays as one continuous take from the tissue's initial placement through the final return to the vowel.

Scientific and Causal Correctness rubric:
level_1: The tissue's movement contradicts the airflow mechanism outright: it stays still during both open-vowel phases, it only moves during the stop-consonant phase, or it is drawn inward toward the mouth during a vowel instead of pushed outward.
level_2: The tissue moves in roughly the correct phase but the pattern is unreliable: its outward motion during a vowel is jerky or stop-and-start rather than sustained, it keeps swaying outward for a noticeable moment after the stop consonant has already begun, or the outward direction of the deflection is ambiguous.
level_3: The tissue deflects and holds (or steadily flutters) outward through the entire first vowel, visibly relaxes back toward hanging straight down once the stop consonant begins, and resumes the same outward deflection once the vowel returns -- its on/off behavior tracks the vowel-stop-vowel sequence correctly.
level_4: All of score 3, and the amount of outward deflection (or flutter amplitude) during the second vowel looks comparable to the first vowel rather than clearly weaker or stronger, and the tissue settles back toward hanging straight down promptly once the stop consonant begins rather than continuing to sway for a long stretch afterward.
level_5: All of score 4, and the tissue's motion during both vowel phases shares a matching visual rhythm (similar flutter speed and steadiness, not merely similar amplitude), and the shift into stillness at the start of the stop consonant reads as an abrupt cutoff rather than a gradual fade -- consistent with the stop consonant fully blocking airflow rather than merely reducing it.

Spatiotemporal Consistency rubric:
level_1: The tissue vanishes and reappears between shots; the mouth or tissue jumps to a different screen position between phases as though two different clips were stitched together; the lighting or overall scene brightness shifts abruptly with no visible cause; the tissue appears to pass through the person's chin or lip as though solid objects overlapped; or the camera cuts to a different framing partway through the vowel-stop-vowel sequence.
level_2: The tissue's position relative to the mouth shifts noticeably between phases with no visible cause (no hand seen moving it); there is a stutter or skipped moment right at a phase transition; the tissue's edge warps or tears unnaturally for an instant; or the framing drifts enough that the mouth is no longer centered by the end of the clip.
level_3: The tissue and mouth keep the same spatial relationship across all three phases without any jump, warp, or cut; the camera framing stays essentially fixed; the tissue's shape stays intact (no tearing or sudden reshaping) even while it flutters. Small, incidental imperfections are acceptable, such as a brief flicker in ambient room light or the tissue settling for a fraction of a second right after it is first placed.
level_4: All of score 3, and the shadow the tissue casts on the person's chin or upper lip moves only in step with the tissue's own visible motion -- it never jumps to a new angle on its own -- the tissue's fibers and texture look continuous from frame to frame with no sudden re-rendering, and there is no mismatch in how the tissue and the mouth shift relative to each other if the head moves slightly.
level_5: All of score 4, and the whole clip reads as one uninterrupted take with no frame freezes, duplicated frames, or motion blur that doesn't match the tissue's actual flutter speed; the apparent light source implied by the tissue's shadow stays in the same place for the entire sequence, so the shadow's position tracks only the tissue's own motion and never shifts for an unrelated reason.