| Annotation -- Action form |
Actions are discrete units of body movement which are not part of body positioning. A body action unit (-AU) is a local excursion of one or a set of articulators (head, trunk, arm, hand) outside a previously held posture configuration and always returns to that or another posture configuration (e.g., head shake, pointing arm gesture). Contrary to posture units, action units occur and change more frequently, and have a very discrete onset (start point), a relatively short duration and a distinct offset (end point). These body actions are performed by the head, shoulders, trunk, arms and legs and involve activities such as nodding, shrugging, gesturing, scratching , kicking etc.
The specific form and dynamics of an action indicate that the movement cannot be considered as the taking of a new posture (form: direction, path, manner; dynamics: no holding of a particular configuration). To code a head, trunk or arm movement as an action, the dynamics and form of the movement (e.g. head nodding, arm gesticulation, scratching) should thus exclude the possibility of simple posture changing. When this necessary condition for action behavior is not fulfilled, the movement should be coded as a postural movement.
Segmentation rules: The onset of an action unit is the time-point when the articulator moves away from the current resting position. The offset of an action unit is the time-point when the articulator has returned to a (resting) position (the initial or a new position). Remark: The returning phase (retraction) may overlap with postural movement. Action units are segmented into a sequence of discrete subunits according to differences in the form properties of the movement. The boundary between two subunits is defined by a discontinuous change (a break or a hold) of the movement direction as specified in the attributes (based on Kita, 1998). When the action shows no discontinuous change in any of the attributes , the onset is simply the time when the head moves away from its position and the offset is the time when the head has returned to a position (the initial or a new position). The direction of an action subunit refers to the movement itself and is coded from its starting point or current position, not relative to the anatomical reference frame. Repetitive movement is not segmented or coded for each repeated cycle separately.| Nodes | |
Head-AU
Container
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Head action unit |
Head-ASU
Container
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Head action subunit |
Trunk-AU
Container
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Trunk action unit. The trunk, or torso, is the upper body excluding the head, neck and upper limbs. It includes the thorax (chest) and abdomen (belly). The thorax extends from the neck to the diaphragm, and does not include the upper limbs. The abdomen constitutes the part of the body between the thorax and pelvis (hip area). Remark: the shoulder belongs to the category of upper limbs. |
Trunk-ASU
Container
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Trunk action subunit |
Left arm-AU
Container
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Left arm action unit |
Left arm-ASU
Container
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Left arm action subunit |
Right arm-AU
Container
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Right arm action unit |
Right arm-ASU
Container
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Right arm action subunit |
AA sym
Container
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Symmetrical arms action. Both arms are involved in an action and are jointly moving in a symmetrical fashion (movement path, direction and manner) |
AA asym
Container
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Asymmetrical arms action. Both arms are involved in an action and are jointly moving in an asymmetrical fashion (movement path, direction and manner). Remark: asynchrony in terms of a few frames is still considered as symmetrical if it is not detectable from normal playback. |
Touch
Container
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One body part touches another body part (self-touch) or an object (object-touch, e.g. clothing) as part of an action. It is not coded when one body part comes into contact with another during the taking or holding of a posture (eg. putting hand on waist, crossing arms). |
| Annotation -- Action form |