Domain: Humanities and Social Sciences — Linguistics
Target concept: A Visual Identification Experiment on the Acoustic Features of Monophthongs and Diphthongs

Video generation prompt: A microphone is connected to the spectrogram interface. The speaker first produces a steady monophthong (/e/), followed by a diphthong (/ei/). The spectrogram is updated in real time, displaying the formant trajectories over time. The left side of the interface shows the spectrogram of the monophthong, while the right side shows the spectrogram of the diphthong. The operator watches both spectrogram panels throughout the recording.

Evaluation guide:
(i) Target concept: Real-time spectrographic distinction between monophthongal steadiness and diphthongal transition in vowel production.
Minimum mechanism: Human vocal tract configuration must change during /ei/ articulation, causing measurable, continuous shifts in resonance frequencies (formants), while /e/ maintains near-constant configuration → producing stable vs. dynamic spectral patterns.
(ii)Storyline: [0s] Microphone connected to interface; [1–3s] Speaker articulates /e/ → left panel illuminates and displays motionless formant bands; [4–7s] Speaker articulates /ei/ → right panel illuminates and displays smoothly evolving formant trajectories; [8–10s] Both panels remain visible and stable in fixed side-by-side positions; viewpoint, lighting, and scale remain invariant; no external interference or UI distraction; all causal links (articulation → spectral change → panel response) are visually contiguous and temporally ordered.

Manual:
Experimental Procedure
1. Connect microphone to spectrogram interface.
2. Speaker produces /e/ steadily → left spectrogram panel activates and displays stable formant bands.
3. Speaker transitions to /ei/ → right spectrogram panel activates and displays shifting formant trajectories.
Observation of Experimental Phenomena
- Left panel: static, parallel, horizontally aligned formant bands (F1–F3).
- Right panel: continuously moving formant trajectories (e.g., F1 falling, F2 rising).
- Side-by-side layout: /e/ always on left, /ei/ always on right.
Summary of Experimental Principles
Monophthongs (/e/) yield steady formant frequencies → stable spectrogram bands. Diphthongs (/ei/) involve articulatory movement → time-varying formant trajectories visible as sloped or curved lines in spectrograms.

Prompt Grounding rubric:
level_1: No microphone is shown; no spectrogram interface appears; there is no left/right two-panel layout; nothing indicates the speaker is producing /e/ or /ei/ in sequence.
level_2: A microphone and a spectrogram interface are both present, but the microphone is not shown connected to the interface, or the interface does not show two distinct panels, or the two panels are not arranged left/right, or the vowels are not produced in the /e/-then-/ei/ order.
level_3: The microphone is visibly connected to the spectrogram interface; the interface shows two panels arranged side by side; the left panel is associated with the speaker's production of /e/ and the right panel with /ei/, in that order; both panels remain on screen once activated.
level_4: All elements of 3-score are present AND each panel activates (lights up or begins updating) only once its corresponding vowel is being produced: the left panel does not activate before /e/ is spoken, and the right panel does not activate before /ei/ is spoken; any on-screen labels for /e/ and /ei/ are legible and attached to the correct panel.
level_5: All elements of 4-score are present AND the microphone, cable, and both panels stay in fixed, unobstructed positions for the full clip with no panel swap, resize, or relabeling; the /e/-to-/ei/ transition is shown as one continuous recording session with no visible cut, pause, or interface reset between the two productions.

Scientific and Causal Correctness rubric:
level_1: Neither panel shows any formant bands; or both panels show identical behavior (both static or both changing); or the frequency axis is inverted, or energy is concentrated in a physically implausible band for a vowel.
level_2: Formant bands are visible in at least one panel, but the behavior is reversed or inconsistent with the vowels: the /e/ panel (left) shows clearly shifting trajectories, or the /ei/ panel (right) shows only flat, unchanging bands.
level_3: The left panel's formant bands stay essentially level across its full duration (consistent with the unchanging vocal-tract shape of the steady monophthong /e/); the right panel's formant bands visibly shift in frequency from the start to the end of its duration (consistent with the tongue and jaw moving during the diphthong /ei/).
level_4: All elements of 3-score are present AND the right panel's shifting bands move in one coherent direction each rather than jumping erratically, specifically F1 trending downward and F2 trending upward across the /ei/ production, matching the vocal tract narrowing and fronting as the tongue moves from the /e/ position toward the closer, fronter /ɪ/-like offglide; no band abruptly jumps, splits, or vanishes in either panel.
level_5: All elements of 4-score are present AND the left panel's F1–F3 bands are evenly spaced, parallel, and essentially flat for its entire duration; the right panel's F1 and F2 bands move smoothly and continuously in the F1-down/F2-up pattern described above with no reversal, stall, or discontinuity partway through; both panels' formant patterns look like plausible vowel spectrograms rather than arbitrary lines.

Spatiotemporal Consistency rubric:
level_1: The spectrogram panels or microphone abruptly appear, disappear, or jump to a different position between frames; the viewpoint suddenly changes or rotates; the /ei/ panel is shown activating before the /e/ panel; the interface flickers or tears apart.
level_2: One panel fades in while the other stays frozen in place with no clear reason; the microphone-to-interface cable is only visible in some frames, as if added afterward; the left/right labels reposition or flash mid-sequence; the spectrogram's update visibly lags well behind the speaker's mouth movement.
level_3: The camera viewpoint and the microphone's position stay fixed for the whole clip; both spectrogram panels, once they appear, remain visible without disappearing or relocating; the /e/ panel is shown first and stays on screen through the appearance of the /ei/ panel; the color and brightness used to render both panels stay the same throughout rather than shifting between frames.
level_4: All elements of 3-score are present AND the /ei/ panel's activation follows the /e/ panel's stabilization smoothly, with no gap in time where neither panel is updating and no moment where both panels overlap or occlude each other; the spectrogram trace appears to track the speaker's vocalization without a visible pause between mouth movement and the corresponding trace appearing.
level_5: All elements of 4-score are present AND both panels keep the same size, aspect ratio, and color scale as each other for the entire clip; the microphone cable traces one continuous, unbroken path from the microphone to the interface with no segment popping in or out; neither panel shows blur, doubling, or misalignment that would suggest the two panels are not sitting in the same flat plane.