Domain: Humanities and Social Sciences — Linguistics
Target concept: Using oral smoke to distinguish plosives from fricatives (pulmonic egressive vs. continuous airflow)

Video generation prompt: A person holds a lit incense stick below the mouth, allowing the smoke to rise. A stop sound is produced first, followed by a fricative sound, with the scene focusing on the mouth and the smoke.

Evaluation guide:
(i) Target concept: Visual differentiation of pulmonic egressive consonants via aerodynamic effect on rising smoke.
Minimum mechanism: Smoke must be buoyant and rise in a smooth, laminar column in still air; the fricative's narrow constriction must generate continuous, sustained airflow strong enough to visibly deflect the smoke for the whole duration of the sound; the stop's full closure must block airflow throughout the hold, so smoke stays essentially undisturbed during the closure, though the release itself (an aspirated burst of air) may produce a brief, momentary puff of smoke disturbance, distinct from the fricative's sustained deflection; articulatory postures must produce functionally distinct airflow regimes (blocked-then-briefly-released vs. sustained constriction).
(ii)Storyline: [Phase 1] Incense stick lit and stably positioned below mouth; smoke establishes vertical laminar rise. [Phase 2] Lips seal fully → airflow halts → smoke continues rising undisturbed. [Phase 3] Lips open briefly then reconfigure into labiodental constriction → continuous turbulent airflow begins → smoke deflects/bends along airstream. [Phase 4] Fricative sustains → smoke disruption persists. [Perspective constraint] Fixed frontal close-up view centered on mouth and incense tip; smoke must be fully visible from ember to mouth entry point; no obstructions; lighting ensures smoke contrast and articulator visibility.

Manual:
Experimental Procedure
1. Person holds a lit incense stick directly below the center of their mouth, ensuring smoke rises vertically into the oral airflow path.
2. Person produces a voiceless bilabial stop (/p/) — lips close completely, hold briefly, then release abruptly with no audible frication.
3. Immediately after, person produces a voiceless labiodental fricative (/f/) — lower lip approaches upper teeth, sustaining narrow constriction to generate continuous turbulent airflow.
Observation of Experimental Phenomena
During the /p/ closure hold: smoke rises steadily and vertically, essentially undisturbed. At the instant of release (the aspirated burst of air that follows opening the lips), a brief, single puff of smoke disturbance may appear — a momentary event, not a sustained deflection, and distinct from what happens during /f/.
During /f/: smoke is visibly and continuously deflected, bent, or dispersed along the airstream path for the entire duration of the sustained turbulent airflow.
Summary of Experimental Principles
Plosives (stops) involve complete oral closure that blocks airflow throughout the hold; the release that follows produces only a brief, transient (aspirated) puff of air rather than continuous airflow, so smoke shows no sustained disruption during a stop — at most a single momentary puff at the release instant.
Fricatives involve a narrow constriction that permits continuous, sustained turbulent airflow — this ongoing airflow interacts with the smoke throughout the sound → visible, sustained deflection or dispersion.

Prompt Grounding rubric:
level_1: No incense stick is visible; no smoke is visible; no person or mouth is in frame; and there is no visible cue of either a stop or a fricative being articulated (no lip closure, no teeth-lip contact).
level_2: An incense stick is visible but is not held below the mouth, or the rising smoke never approaches the mouth region, or the person is shown with the mouth occluded or out of frame; at most one of the two articulatory postures (full lip closure, or teeth-lip contact) is discernible, never both in sequence.
level_3: The incense stick is held below the mouth with smoke visibly rising toward the mouth region; the mouth is fully visible and unobstructed; two distinct articulatory postures occur one after another: a full bilabial closure (lips sealed together) followed by a labiodental contact (lower lip against upper teeth), each held long enough to be told apart by eye.
level_4: Everything in score 3 holds, and the smoke rises as one continuous, unbroken stream from the ember for the whole clip with no cuts; the bilabial closure shows no visible gap between the lips; the labiodental contact clearly shows the lower lip touching the upper teeth rather than merely approaching it; both postures occur within a single continuous shot from a fixed viewpoint.
level_5: Everything in score 4 holds, and each posture is held with stable, correct geometry for its entire duration: no leakage visible at the lips during the whole closure hold, and continuous lower-lip-to-upper-teeth contact for the whole fricative hold, matching the expected mouth shapes for English /p/ and /f/; the switch between the two postures is clean, with no ambiguous in-between mouth shape lingering on screen; nothing about the lighting or camera framing obscures the view of the mouth at any point.

Scientific and Causal Correctness rubric:
level_1: The smoke behaves the same way during both sounds, with no visible difference in its trajectory, density, or continuity between the stop and the fricative; the mouth shows no functional difference between the two postures; nothing on screen supports a causal link between articulation and smoke behavior.
level_2: The smoke shows only incidental variation (a slight tremor or brightness change) between the two sounds, with no directional or structural difference; the mouth's shape differs between the two sounds but not in a way that reflects the stop/fricative distinction (e.g., both look like an open mouth, or both look fully closed); no causal relationship between articulation type and smoke behavior can be read from the footage.
level_3: During the fricative's constriction, the smoke visibly bends, splits, or scatters in a way consistent with continuous turbulent airflow; during the stop's closure hold, the smoke rises essentially undisturbed; the mouth postures match their sound class (full closure for the stop, narrow labiodental constriction for the fricative), so a basic cause-and-effect chain (closure blocks airflow so smoke stays steady; constriction lets air through so smoke is disturbed) is visible.
level_4: Everything in score 3 holds, and the fricative's smoke disruption is sustained for the whole length of the constriction and stops when the fricative ends; during the stop, the smoke shows no sustained disturbance throughout the closure hold; at most, a single brief puff of disturbance may appear exactly at the moment of release (consistent with a natural aspirated burst of air), but this is a momentary event, not an ongoing deflection like the fricative's.
level_5: Everything in score 4 holds, and the contrast between the two sounds is unmistakable: the fricative shows continuous, sustained smoke deflection tracking the entire constriction, confined to the airstream path near the mouth rather than disturbing the whole scene, while the stop shows a steady, undisturbed smoke column through the entire closure hold with, at most, one momentary puff coincident with the release burst: never a sustained deflection during the stop, and never a lapse into stillness during the fricative.

Spatiotemporal Consistency rubric:
level_1: The incense stick suddenly appears in a different position between frames; the mouth disappears and reappears; the smoke plume vanishes and re-emerges instead of rising continuously; the shot cuts to a different framing or angle mid-sequence; the scene's lighting swings abruptly between bright and dark with no cause; the background shifts in color or texture with no explanation; or the person's head snaps to a new position with no motion in between.
level_2: The incense stick shakes erratically with no settling; the smoke flickers or pulses in brightness in a way unconnected to the articulation; the mouth region abruptly changes size or position between frames; or there's a visible jump or cut between the stop phase and the fricative phase.
level_3: The incense stick shows only slight unsteadiness in position; the smoke's opacity fluctuates slightly but not in sync with the articulation; the framed mouth region drifts only slightly (less than about 10% of the mouth's width) over time but stays clearly in view; the scene's lighting stays visually steady throughout, with no sudden brightening, darkening, or shift in shadow; the whole clip is one continuous take with no cuts.
level_4: Everything in score 3 holds, and the incense stick stays visually fixed relative to the mouth for the whole clip; the smoke rises with smooth, unbroken continuity, with no visible gaps, freezes, or teleporting puffs; the mouth stays framed in essentially the same spot throughout; focus and framing stay constant; the head, lips, and smoke all move in a physically natural way, with no floating smoke or rigid snapping of the articulators.
level_5: Everything in score 4 holds, and the incense stick and mouth keep a visibly constant spatial relationship with no perceptible drift or shake; the smoke's rise looks continuously natural, at a steady speed and density, rather than looping or resetting; the lips and jaw move fluidly between the stop and fricative postures with no stutter, freeze-frame, or doubled image; focus, exposure, and framing look identical from the first frame to the last.