The Structure category

The movement units as identified in Step 1 are further classified according to the Structure category (Figure 1, Step 2). The Structure of a movement unit is the 'construction' of the movement. It is primarily defined by the trajectory, the

dis-placement, and the velocity. Therefore, the Structure values can be used in ki-nematographic investigations (Chapter 6). In addition to these criteria, human raters consider the presence/absence of efforts (Laban, 1988) and for hand movements, the presence/absence of hand shaping.

There are specific combinations of trajectory, displacement, and velocity.

Based on some of these combinations, for certain movement units, specific phases can be identified, e.g. a one-dimensional trajectory with an increase in velocity and typically a centrifugal path characterizes a transport phase. Basi-cally, three phases can be identified by the specific trajectory - displacement - velocity combinations: transport phase, complex phase with the subtypes motion complex phase and static¹¹ complex phase, and retraction phase. In NEURO-GES, movement units that show these phases are termed "units with a phase structure". Given their defined structure, it is evident that these movement units are discrete in time. Those movement units that do not show at least a complex phase are termed "units with no phase structure". They can be potentially con-tinuous in time.

Five Structure values are distinguished: (i) irregular, (ii) repetitive, (iii) pha-sic, (iv) aborted, and (v) shift. Short definitions of the Structure values are given in Table 2. The kinematographic descriptions in Chapter 6 further illustrate the characteristic patterns of trajectory, displacement, and velocity for each Struc-ture value.

Table 2 Short definitions of the Structure values Structure value Short definition

irregular movement with no phase structure; trajectory with short paths in various directions; practically no displacement between beginning and end of unit; potentially continuous in time

repetitive movement with a phase structure; a motion complex phase in which the same movement path is used repetitively; discrete in time

phasic movement with a phase structure; a static complex phase, in which there is transient motionlessness in an anti-gravity position, or a motion complex phase, in which the movement path is one-way;

discrete in time

aborted transport and retraction phase only; discrete in time; often no dis-placement

shift displacement of the hand from a rest position / posture to another one; the trajectory basically equals the displacement; discrete in time

11 The term static (stroke) is adopted from Mandana Seyfeddinipur (personal communica-tion).

Phasic and repetitive units are characterized by a phase structure, i.e., they typically contain a preparation phase, a complex phase, and a retraction phase.

The preparation phase evidences that (implicit or explicit) planning processes are ongoing. In this phase the realization of the complex phase is prepared by moving the part of the body to a specific location where the complex phase is executed. Thereby it is evidenced that the complex phase is "something" that has been planned. In line with propositions from gesture research concerning the stroke phase in gesture (e.g. Kendon, 1972; McNeill, 1992; Seyfeddinipur, 2006), it is proposed here that the complex phase is the realization of a concept (however, in NEUROGES the identification of phases not only refers to ges-tures, but also to self-touches, actions, and expressive motions). "Concept may be tentatively defined as a representation formed in the mind by generalizing from particulars, and conceptual thinking as the process of performing the op-erations required to form and handle concepts." (Vignolo, 1999). Based on this definition, it is proposed here that phasic and repetitive units are associated with conceptual thinking. These units can be displayed explicitly or implicitly. Fine-grained movement analysis as well as neurobiological and neuropsychological investigations can distinguish between the explicit and implicit display.

However, phasic and repetitive units seem to differ with regard to cognitive complexity. Some evidence for this proposition is provided by motor control research and by clinical observation. Applying approximately comparable val-ues, motor control research demonstrates that "single" movements are associated with more complex cognitive processes than repetitive movements, in which the part of the body moves back and forth on the same path. The latter are reported to partly rely on routine processes (Mourik & Beek, 2004; Spencer et al., 2003;

Schaal et al., 2004; Huys et al., 2008). Thus, phasic units may rely on novel conceptualizations, while repetitive units seem to be associated with routine concepts.

In contrast to phasic and repetitive movements, irregular movements have no phase structure. In irregular movements the respective part of the body is not moved to a specific location to execute a complex phase, but it starts moving where it happens to be. These movements are not based on conceptual thinking but they are non-conceptual sensory-motor activations. By moving the part of the body they provide - potentially ongoing - motorsensory stimulation. It is proposed here that, thereby, they serve to regulate arousal. Arousal is the degree of activation of the central nervous system ranging from hyper- to hypoarousal.

Irregular movements are displayed beyond the mover's awareness. As irregular units lack a phase structure, from the observer perspective their beginning, dura-tion, and ending is unpredictable. In some individuals, irregular movements are continuously ongoing in a given context, being only interrupted by conceptual movements or by shifts.

On this background, the three values irregular, repetitive, and phasic are or-dered with regard to the level of cognitive complexity on an axis from non-conceptual to complex non-conceptual.

Figure 2 Structure values and level of cognitive complexity

A shift is a direct transition between two rest positions / postures. As exposed in Section 2.1, rest-positions and postures reflect emotional-cognitive-interactive states. Accordingly, shifts evidence changes of these states. Shifts are typically displayed implicitly. It is proposed here that a particularly high frequency of shifts between rest positions reflects that the individual does not find a position to rest in for a longer time. With regard to emotional, cognitive, and interactive processes, it might indicate that the individual does not find a state to stay in.

Likewise, a particularly low frequency of shifts reflects that the individual does not leave the position.

Aborted units occur most often in bimanual units. The aborted unit in one limb then co-occurs with a complete phasic or repetitive unit in the other limb.

This constellation reflects a lack of suppression of ipsilateral motor pathways controlling the non-dominant hand (Zülch & Müller, 1980; Lausberg et al., 2000; Zijdewind & Kernell, 2001; Westenberg et al., 2004; Lausberg et al, 2007). While the concept is to be executed unimanually by the dominant hand, the other hand, which displays the aborted unit, is co-activated (despite the con-cept) and then stopped. Unimanual aborted units are typically disruptions of movements that would have potentially developed to a phasic and repetitive unit. Seyfeddinipur (2006), who uses comparable values for gestures, reported in her analysis on speech-gesture coordination that, among others, these values co-occurred with speech disfluencies, and, more specifically, indicated an aban-donment of the original speech plan (Seyfeddinipur, personal communication, 2011). Thus, aborted units reflect a disruption of concept realization. However, also shift movements can be aborted. In this case, there is a disruption in the process of adopting a new rest position or posture.

To summarize, irregular, repetitive, and phasic units are proposed to rely on processes with different levels of cognitive complexity ranging from non-conceptual via automatic non-conceptual to novel non-conceptual. Shifts are transitions between two rest positions / postures. Aborted units comprise different forms of disruptions in the execution of conceptual and shift movements.

After the Structure category coding, the assessment of the head and trunk movements stops for the time being. In Module III, the head and trunk Structure units that have a phasic or repetitive Structure are further assessed (indicated in Figure 1 by the right bar above the Step 3 rhombus). The Focus category as well as the subsequent Module II Contact and Formal Relation categories only serve for the further analysis of limb movements.