Domain: Humanities and Social Sciences — Education
Target concept: Visual signs of sign language: gestures are performed in front of the chest and combined with facial expressions.

Video generation prompt: The teacher demonstrated a series of standard sign language expressions for Hello, nice to meet you with smooth and natural movements.

Evaluation guide:
(i) Target concept: Sign language as a visual-gestural language that conveys meaning through coordinated manual signs (handshape, location, movement) and nonmanual signals (facial expression, head position), illustrated here through a classroom demonstration of the two-sign greeting sequence Hello, then nice to meet you.
Minimum mechanism: The teacher's upper body must stay visible and stable in frame; for this demonstration both signs are performed within a chest-anchored signing space, the specific convention shown here (not a claim that every sign in every sign language must be produced at chest height; many signs, including some greetings, are produced near the face); a distinct facial expression (eyebrow raise plus forward head tilt) must accompany the nice-to-meet-you sign; the two signs must appear in the fixed order Hello, then nice to meet you.
(ii)Storyline: Frame opens on stationary teacher facing camera → Hello sign begins with the dominant hand rising into the chest-level signing space and completing its rotation → hand returns to a neutral rest position (a brief pause that does not break visual continuity) → both hands rise into the chest-level space with an upward arc for nice to meet you → eyebrows lift and head tilts forward together with the hands' ascent → hands settle back at chest level → expression relaxes. All actions occur from a fixed frontal viewpoint; no camera motion; the signing space stays anchored to the torso; facial-expression changes are visible and timed to each sign's movement phase.

Manual:
Experimental Procedure
1. Teacher stands facing camera, upper body centered in frame.
2. Performs “Hello” sign: dominant hand, flat palm, fingers together, rotates inward while moving from side toward chest center.
3. Immediately follows with “nice to meet you” sign: both hands, flat palms, fingers together, rise upward from waist level with gentle arc while eyebrows lift and head tilts slightly forward.
Observation of Experimental Phenomena
- Two distinct, sequential hand configurations appear in chest-area signing space.
- Facial expression changes: neutral → eyebrow raise + forward head tilt between signs.
- No hand crossing, face-touching, or waist-level signing observed.
Summary of Experimental Principles
Sign language relies on simultaneous manual (handshape, location, movement) and nonmanual (facial expression, head position) components; grammatically required facial expressions must co-occur with specific lexical signs.

Prompt Grounding rubric:
level_1: No sign-language gestures appear; no human upper body is visible; no chest-level signing space is used; no facial expression is visible; neither the Hello sign nor the nice-to-meet-you sign is represented in any form.
level_2: A human upper body appears in frame, but the signing hand(s) work away from the chest-level space specified for this demonstration (e.g., only near the face or at waist height); at most one recognizable sign shape appears, with no clear second sign for nice to meet you; facial expression is absent or unchanging throughout.
level_3: Human upper body is centered and stable; both hands perform their movements within the chest-level signing space; two sequential gestures appear in order (first Hello, then nice to meet you), each with a distinguishable handshape and hand orientation; a facial-expression change occurs at some point, but it is not tied to the correct sign (e.g., it appears during Hello instead of nice to meet you, or is missing for one of the two).
level_4: All elements from score 3 are present AND a facial-expression change (eyebrow raise plus head tilt) is visibly present specifically during the nice-to-meet-you sign, as its own component alongside the two hand signs; the sequence is strictly Hello → nice to meet you with no repeated, omitted, or reordered sign; no extra gestures unrelated to the two target signs appear in frame.
level_5: All elements from score 4 are present AND both signs are performed in full, from initial hand formation to final resting position, with no truncation or early cutoff from framing or occlusion; the facial-expression component lasts for its full duration rather than a brief flash; both hands and the face stay within the camera frame for the entire sequence with no body part leaving and re-entering the shot.

Scientific and Causal Correctness rubric:
level_1: Handshape, location, movement, and facial expression bear no coherent relationship to each other or to any recognized classroom sign for Hello or nice to meet you; the depicted gestures would not be recognized as either sign in a standard K–12 sign-language greeting lesson.
level_2: One sign approximates its target handshape (e.g., a flat hand for Hello) but its location or movement path contradicts the standard classroom form (e.g., tapping the forehead or waist instead of the chest-level space taught for this sign); the second sign is not recognizable as nice to meet you; facial expression is neutral or contradicts the sign's meaning (e.g., a frown appears during nice to meet you).
level_3: Both signs use the correct handshape and the chest-level location taught for this greeting pair; movement direction and path match the standard classroom form for each sign; a facial expression appears for one sign but is missing or misplaced for the other (e.g., eyebrows raise during Hello, where none is expected, while nice-to-meet-you stays neutral, where a raise is expected; or the reverse pairing occurs).
level_4: All sign parameters (handshape, orientation, chest-level location, movement path, and the accompanying nonmanual signal) are correct for both Hello and nice to meet you as taught in standard K–12 sign-language greeting lessons; the eyebrow raise and forward head tilt occur specifically with nice to meet you as its grammatical marker; neither sign is substituted with, or blended into, the other.
level_5: All elements from score 4 are present AND every nonmanual signal (eyebrow position, eye gaze, head tilt) is fully coordinated with the correct manual sign: full eyebrow raise, sustained eye contact, and forward head tilt occur only during nice to meet you, while neutral eyebrows and a level, direct gaze occur during Hello, with no partial or misplaced activation of either signal.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the teacher's body jumps instantly to a different position in frame with no motion in between; a hand or arm goes missing mid-gesture and reappears elsewhere; an abrupt, unmotivated lighting or background change occurs; a frame drop causes a visible jump that skips over an entire sign.
level_2: Moderate inconsistency: the teacher's upper body shifts to a clearly different position or scale in frame between the two signs (an obvious, large repositioning rather than a subtle drift); one hand stays fully hidden behind the body or out of frame for an entire sign; the facial expression freezes while the hands move, or the hands freeze while the expression changes; the background flickers or warps during the motion.
level_3: The teacher's position drifts only slightly and barely noticeably between the two signs, without breaking the chest-level signing space; one brief moment of partial hand occlusion occurs during a single sign; the facial-expression change is visible but noticeably lags behind the start of the corresponding hand movement; the teacher's shirt color and the background stay visually stable with no flicker.
level_4: No noticeable drift in the teacher's position or occlusion of the hands occurs; the signing space stays visually anchored to the torso throughout; facial expression and hand motion begin together for each sign with no perceptible lag; the teacher's clothing, skin tone, and background remain visually stable across the whole sequence with no flicker or warping.
level_5: All elements from score 4 are present AND the hand and arm motion flows smoothly through both signs and the transition between them, with no visible stop-start hitch, freeze, or restart; joint movement looks anatomically natural throughout (no impossible wrist or elbow bends); the hands and face show no visible ghosting, blurring, or doubling that would make either sign hard to make out.