Knowledge Accumulation in Theatre Rehearsals: The Emergence of a Gesture as a Solution for Embodying a Certain Aesthetic Concept

Theater rehearsals are (usually) confronted with the problem of having to transform a written text into an audio-visual, situated and temporal performance. Our contribution focuses on the emergence and stabilization of a gestural form as a solution for embodying a certain aesthetic concept which is derived from the script. This process involves instructions and negotiations, making the process of stabilization publicly and thus intersubjectively accessible. As scenes are repeatedly rehearsed, rehearsals are perspicuous settings for tracking interactional histories. Based on videotaped professional theatre interactions in Germany, we focus on consecutive instances of rehearsing the same scene and trace the interactional history of a particular gesture. This gesture is used by the director to instruct the actors to play a particular aspect of a scene adopting a certain aesthetic concept. Stabilization requires the emergence of shared knowledge. We will show the practices by which shared knowledge is established over time during the rehearsal process and, in turn, how the accumulation of knowledge contributes to a change in the interactional practices themselves. Specifically, we show how a gesture emerges in the process of developing and embodying an aesthetic concept, and how this gesture eventually becomes a sign that refers to and evokes accumulated knowledge. At the same time, we show how this accumulated knowledge changes the instructional activities in the rehearsal process. Our study contributes to the overall understanding of knowledge accumulation in interaction in general and in theater rehearsals in particular. At the same time, it is devoted to the central importance of gestures in theater, which are both a means and a product of theatrical staging.


Introduction
Rehearsing can be described as an institutional and professional activity of knowledge accumulation in which a production crew collaboratively develops a production-specific interactional history (Deppermann, 2018), which includes agreements about what is to be performed. In contrast to typical learning settings, such as driving school, knowledge accumulation in creative settings, such as theater rehearsals, is an open, collaborative process in which solutions are not predetermined but stabilize over time as an emergent product (Deppermann & Schmidt, 2021). Drawing on a multimodal extended EMCA-approach (See Sect. "Data and method"), this paper investigates the process in which professional actors and a director develop shared knowledge over time in a single rehearsal process. The data comes from rehearsals of The Oral Betrayal (der mündliche Verrat), a music theater piece by the composer Mauricio Kagel (1981Kagel ( -1983, played in spring 2013 at the National Theater in Mannheim (Germany).
To make the process of knowledge accumulation traceable, we focus on the emergence of a single gesture. Our starting point, from which we then 'look back' at the emergence of the gesture (See. Sect. "The emergence of a gesture and an aesthetic concept"), is a case in which the director (D) uses this gesture to instruct the actors. Interestingly 'the same gesture' is simultaneously co-produced by one of the actors. Chronologically, this is the last extract within our seven selected extracts (see Sect. "Data and method"), one day before the opening night: a Transcripts follows the conventions of GAT2 (Selting et al., 2011) and Mondada (2019). Italics are used for marking spoken script lines.
In line 1, D instructs the actors to play a scene again (line 2: 'once the whole thing with') in a certain manner, which is not described verbally but expressed by a hand gesture in which the director rubs both hands together (Fig. 1). The same gesture is co-produced by Actor 1 at precisely the same time (line 2; Fig. 1). This collaborative embodied completion (Keevallik, 2015) not only shows that the meaning of the gesture is obviously shared but that its deployment at this position was projectable for the actor.
This 'rubbing-hand-gesture' has a basic conventionalized meaning. 1 However, in this context it refers to a certain manner in which to play the scene which is not covered by its conventional meaning but attributable to its emergence within an interactional history in this community of practice. Thus the verbal phrase together with the gesture is not only highly indexical, but also not understandable to outsiders. The verbal part together with the gesture forms a "syntactic-bodily gestalt" (Keevallik, 2015: 309), in which a linguistic structure is completed by embodied resources to form a recognizable action. The ensemble treats the director's instruction as unproblematic by implementing the instruction and the gesture. Actor 1 is performing the same gesture at the same time (line 2, Fig. 1) 2 and the ensemble form up and start to play, with Ac2 producing the first line of the script (line 5). Furthermore, Ac1 and Ac3 integrate the gesture into their play (Fig. 2).
The unproblematic following of the director's instruction and especially the coproduction of a crucial part of it ('the gesture') are strong indicators for shared knowledge between the participants. In coordinating their activities, the participants Director and Actor 1 produce the same gesture at the same time (from different camera angles) 1 The English Wikipedia lists "hand rubbing" (s. Wikipedia contributers, 2021) as an emblematic gesture conveying "in many cultures either that one has a feeling of excited expectation, or that one is simply cold" (https:// en. wikip edia. org/ wiki/ Hand_ rubbi ng). A similar meaning is noted in The American Heritage Dictionary of Idioms (Ammer 2003) for "rub one's hands": "Experience or exhibit pleased anticipation or self-satisfaction". 2 Which nicely shows that the gesture is not merely imitated. obviously rely on knowledge that they have built up during their rehearsals and that is only available to these members of this community of practice in this particular setting. Thus, the gesture obviously has a community-specific history.
Our study adopts a longitudinal perspective Pekarek Doehler et al., 2018) and uses the example of this gesture's emergence to track processes of knowledge accumulation in interaction. Our first goal is to identify the interactional practices by means of which the participants collectively and step-by-step build the shared knowledge necessary to understand both the instruction and the gesture. Second, we aim to show how practices change (for example: that instructions become more condensed). Third, we are interested in how gestures in theater (rehearsals) in general and this specific gesture in particular are used as bodily means to develop and embody aesthetic concepts.
In the following, we first present background regarding common ground and gestures in theater. After a section about data and method, we show in the analysis how the gesture emerges in the course of the rehearsal. For this purpose, seven instances where the same scene is rehearsed are longitudinally investigated. We close with a summarizing discussion.

Common Ground and Gestures in Theater
To rehearse is to investigate and decide on the routine (cf. Schmidt & Deppermann, in this volume) of the performance, and to accumulate the shared knowledge that is needed to coordinate the performance. Rehearsing is understandable as a process of grounding (Clark, 1996: Ch. 8), a basic moment-by-moment local process through which participants build common ground. Knowledge grounded in interactional histories affects the way participants interact and process information (Enfield, 2008) -as in the example above, where the director can rely on all participants being able to follow his condensed and indexical instruction. Clark (1996) divides common ground (CG) into communal CG, which refers to knowledge among members of a given society, and personal CG, which refers to knowledge shared with specific individuals. It is this latter kind of knowledge, based on interactional histories and grounded in biographical, individual experiences that is produced and relied upon in theater rehearsals.
How interactional histories impinge on how participants act and understand each other in interaction is recently brought in focus by longitudinal studies in EMCA Pekarek Doehler et al., 2018). Most longitudinal studies in EMCA so far focus on settings in which learning or developmental aspects play a major role (see Deppermann, 2018;Pekarek Doehler et al., 2018;Wootton, 1997). Similarly, we focus on a setting where 'learning' in a broad sense plays a role. However, two peculiarities should be mentioned that have to do with the way knowledge is produced in theater rehearsals.
First, in theater rehearsals, knowledge accumulation is explicitly in focus and secured through sequences of instructions and embodied implementations, which display an understanding (Hindmarsh et al., 2011). The continuous and exposed process of negotiating knowledge in rehearsals leads to a cohort-specific personal common ground that accumulates over an interactional history of specific participants (Weeks, 1996) forming a transient community of practice (Deppermann & Schmidt, 2021;Hazel, 2018). This distinguishes theater rehearsals from everyday settings and many (language-centered) learning settings in which understanding remains comparatively opaque (Koschman et al., 2001).
Second, in contrast to most learning settings, theater rehearsals are open co-creative activities. There are no learnables (Zemel & Koschman, 2014) to be taught like in driving lessons (cf. Deppermann, 2018), airplane training (Melander, 2009), medical training (Zemel & Koschman, 2014;Hindmarsh & Pilnick, 2002) or in class-room interaction (Mehan, 1979); rather, (new) ideas must be developed and tried out. Rehearsing is not about evaluating (and if necessary correcting and improving) a "projected outcome" (Amerine & Bilmes, 1988:329) on the basis of defined standards, but about developing joint ideas and trying out possible implementations of these ideas (Hazel, 2018;Norrthon, 2019). In our case, the gesture used by the director is neither a learnable, in the sense of something that already existed before the rehearsals and now has to be taught, nor is its emergence subject to a planned process. Our gesture has to be learned (in the sense of 'remembered'), but it was not given as a pre-defined 'learnable'.
To investigate the interactional history of a gesture during rehearsals is to direct the interest toward essential features of theater. Theater is about 'show, don't tell' and naturally, the embodied nature of the art-form is not only linked to finished performances, but also to the procedures behind them, the production process. The classic conception of gesture in theater considers gesture as a medium of expression (Oxford dictionary). However, gestures not only play a fundamental role in executing but also in developing the performance. Thus, gestures in theater are also means for production (cf. Pavis, 1998:162), i.e., a form of expression that can be explored and experimented with in order to develop suitable forms of representation. The word gesture comes from the Latin gestus, which stands for both attitude and embodied actions. This duality is important in Bertolt Brecht's theories of theater (Brecht, 1964). A key concept in Brecht's theory of gestus is Haltung, which is used for both a mental state and a physical expression (Barnett, 2015: 97). The term is used also in the examined data (See Sect. "The emergence of a gesture and an aesthetic concept"), and we are keeping the German word Haltung in this article to avoid the risk of losing the double meaning of the term. Haltung can be described as "a gesture that is held" (Pavis, 1998: 30). At the same time, it can refer to an inner state, an attitude. Gesture is used as a resource to work on a general task in theater, namely how to embody concepts. As we will see, this is exactly what our gesture does.

Data and Method
In our study, we track "the process of emergence" : 21) of a given resource (in our case a gesture) in a community of practice drawing on both a multimodal extended EMCA-approach (Deppermann, 2013) and longitudinal CA . Deppermann & Pekarek Doehler (2021: 128-133) differentiates three kinds of approaches to longitudinal CA: developmental studies, studies of sociohistorical change and studies of joint interactional histories. Our study belongs to the latter type of studies which "set out to evidence the cumulative nature of joint experiences" (131) in a community of practice. The basic aim of longitudinal CA, tracking change, requires addressing certain methodological issues that have not been a main focus in EMCA to date. First, collection building is oriented to the chronological flow of time. In this sense, we are able to speak of the extract we presented above as our 'last' instance. Second, instances of a collection should be comparable. In our case, we focus on the emergence of a single gesture, and keep participants, activities (sequences of instructions) and focus (repeated rehearsals of a particular scene) roughly the same. Third, with respect to the dimension of change, we focus on knowledge accumulation in a community of practice and how this changes interactional practices within this community. Fourth, with respect to time scales we adopt a "micro-genetic" (Wagner et al., 2018:16) approach, tracking interactional histories based on a collection of instances on a time-scale of two months (for similar approaches s. Deppermann, 2018: 295-296;Deppermann & Schmidt, 2021;Schmidt & Deppermann in this volume;Hazel, 2018;Norrthon, 2019). A fifth issue of longitudinal CA is how 'complete' or 'gapless' selected instances can represent processes of change. We address this problem by focusing on theater rehearsals that have a clearly defined time frame (about two months) and that we have tried to capture as completely as possible.
Our data come from professional theater in Germany; we videotaped the rehearsal process of a production called The oral betrayal, a music theater piece by the composer Mauricio Kagel, played in spring 2013 at the National Theater in Mannheim. The piece has no plot, but combines text fragments dealing with the devil with noisy, live music. The rehearsals included sessions with and without the musicians; we will focus on the rehearsals concerned with acting. The process of developing the acting scenes (without the musicians) took only one week in total. The video recordings, altogether 24 h, were made with two cameras covering the director and the ensemble (see Fig. 2). In addition, we collected ethnographic data, including interviews with participants, field notes taken during participant observation, and documents, particularly the script.
For our purpose of tracing the emergence of a gesture, we have selected seven instances in which a particular scene is rehearsed in relation to a particular aesthetic concept that is later both expressed and referred to by the gesture shown above. These seven examples cover all instances without gaps where either the concept we are interested in is mentioned and/or the gesture is produced.
In the next section we track the emergence of the gesture starting at the very beginning of the rehearsals where the scene is implemented for the first time.

Introducing the Concept
In our second extract (chronologically speaking the first) the three actors and the director (see Fig. 2) discuss a scene in which the script text is presented as a trialogue. The three actors are standing side-by-side directly facing the audience while they are supposed to produce alternating short lines of text at a fast pace. Before they start to play, the director introduces for the first time a concept for how the scene could possibly be played by referring to a specific Haltung. He refers to this concept as 'Spielerhaltung'; 'gambler attitude' (line 45), the very concept that is later embodied by the 'rubbing-hand-gesture' we saw in extract 1. We join the action when the participants quote the script with 'the dice rolled' (line 1 and 2) in preparation for the upcoming start of playing the scene: a In the following transcripts, we marked verbal references to the gambler attitude and occurrences of the rubbing hand gesture with grey shadings. b Italics are used for marking spoken script lines.
In this first extract, the director introduces a Haltung on how to play the scene. He develops his idea in several argumentative steps: • First, he repeats Ac3's quote of the script (line 1: 'the dice rolled' in line 2) and states that 'that is exactly the motto of the text' (line 4). By picking up her quote 1 3 Knowledge Accumulation in Theatre Rehearsals: The Emergence… as a starting point, he roots his idea in an intersubjectively shared source that is central to theatre, namely the script. • Before he specifies the announced motto much later (line 18 with 'it is about game'), he refers to the cognitive process he has gone through (lines 13, 10: 'what I've now …. understood') in order to understand the crucial meaning of the line quoted above (lines 15-17: 'what is the most important thing for the text is indeed 'and the dice rolled''). In this way, the motto of the text is presented as a result of an interpretation of the textual basis of the play: 'it is about game' (line 18). • Then, the game-motto, taken from the script, is used to derive a Haltung (line 22), at this point specified as a membership categorization device (Sacks, 1992): 'competitors' (line 23). In addition, he delivers accounts for his idea: Since theater is always a 'Spiel'; (play/game), 3 they should now address the audience directly and pretend to play with them (lines 25, 26). • In addition, the motto game is used to resolve previously mentioned inconsistencies and, by that, also to pre-empt any possible resistance by the actors (lines 29-41). The seemingly disturbing 'music', a critique mentioned in previous discussions by Ac3 ( After a longer narrative of D's propensity for gambling (1:40 min, not part of the transcript), the director explains what 'the gambler attitude' means practically for the performance of the actors and especially for orally animating the text: 'that you take the text away from each other than at some points' (lines 189, 190). In response to Ac3's complaint (line 192: 'I think at first once we now also have to', what can be paraphrased as: 'we should first try that out'), he re-frames (and justifies) his previous explanations and rather conceptual instructions as 'that was just about the basic attitude' (line 195). At the same time, he assigns the concept an essential, overarching status being omni-relevant (referred to as 'Grundhaltung'; 'basic attitude') when playing the scene.
In this first extract, we have seen the director developing a concept that specifies the attitude with which the scene should be played. He provides the concept with a label ('gambler attitude') and explains it verbally. In this first extract, there are no realizations of how to implement the concept bodily; most significantly for our focus, the gesture introduced above has not appeared yet. Although there are some more concrete instructions (e.g. in line 189), it remains a problem how to implement the concept -as the following extracts will show.

Developing and Adopting the Concept Through the Production of an Embodied Solution ('the Gesture')
In the second instance on the same rehearsal day 37 min later (Ex. 3), the director reminds the actors of the gambler attitude. Most importantly, in this second try-out of the scene, Ac2 puts his hands together and rubs them (line 20):

3
After the participants agreed to play the scene again (lines 1-7), the director reminds the ensemble to 'not forget the basic attitude gambler' (line 8). On the one hand, using the label with a definite article ('the') without any explanations,

3
Knowledge Accumulation in Theatre Rehearsals: The Emergence… he assumes common ground building on his prior introduction of the concept (see extract 2). 5 In this respect, the concept is treated as taken-for-granted. On the other hand, having to remind the ensemble of the concept treats it at the same time as a part of the scene that has not yet become routine.
The ensemble's responses show that the concept is not yet accepted as an unproblematic part of the shared knowledge of how the scene should be played. Instead of playing the scene with the demanded attitude, the start of the scene-play is considerably delayed (until line 35) and -instead -the concept is challenged. Nevertheless, one of the actors produces the gesture (line 20), which is later used to refer to the concept: • First off, there is a lack of uptake: After a long pause over two seconds (line 9) only Ac3 produces a minimal uptake, 'uhu' in line 10 and, after another half-second pause (line 11), 'okay' in line 12. In addition, Ac3's 'uhu' (line 10) is hearable as a change-of-state-token (Heritage, 1984) (a variant of German ach/aha; cf. Golato & Betz, 2008, Golato, 2010 which challenges D's assumed shared knowledge of the concept and deontically contradicts D's instruction by treating it as news rather than an announcement to be complied with (Stevanovic & Peräkylä, 2012). • Afterwards there are several mock implementations of the concept which display a jocular resistance. Again, the start of playing the scene is delayed. Instead, D's claim how the scene should be played is ridiculed. In line 13, Ac2 starts a first mock implementation that exaggerates (or: hams/over-plays) selected features of the concept in which Ac3 joins in (line 13). After a pause (line 15), Ac2 starts another mock implementation; this time he fictionally expanding the concept by playing a gambling addict. The mock implementations, mainly invented by Ac2, are collectively constructed as laughables (lines 14, 19, 20, 26).
In addition, Ac2 displays category bound activities typical for gamblers like pulling levers on a slot machine, pressing buttons, and winning money (Fig. 5, line 13).
He also invents corresponding text lines (lines 23-25: 'give the two euros') and involves his fellow actors (line 23) in the process. Thereby the concept is narrowed down to the semantic field of gambling addiction. Most important for our interest, the rubbing-hand-gesture appears in different versions as a part of the mock implementations (figs. 3 and 8) and also, as a reduced version (only rubbing the fingers of both hands individually), in the performance started in line 35 (Fig. 9). At this point, the gesture (still very variable in its execution) is beginning to become an integral part of a holistic (pantomime-like) representation of a conceptual-driven (gambler attitude) stereotype (a gambling addict); there is no explicit focus on the gesture (indeed, focusing it at this point is only possible in retrospect) and it is not yet perceived as an independent expression that relates to the yet-to-be-defined attitude. The two involved tasks -establishing an attitude (gambler/gambling) and finding  D evaluates Ac2's performance positively without explicitly addressing the mocking. In line 21, he verbalizes a positive effect from an audience's perspective ('that instantly amuses me'); in line 31, he delivers an account for why Ac2's performance is consistent with the concept ('then it also features a bit like something challenging'). In evaluating the mock versions positively, D treats them as valid 'proposals' to a solution of how to embody and thus play the scene with a 'gambler attitude'. With this, he selects certain ways of playing the scene and encourages the actors to  keep these elements in the following performances of the scene. When the actors start to play the scene (line 35), Ac2 adopts in a toned-down way the elements previously shown within the mock implementations (Fig. 9).
Both the reminder of the director and the reluctance of the ensemble show that the concept is not (yet) taken-for-granted. Nevertheless, the first concrete ideas are developed as to how the scene can be played; one of these are different versions of the rubbing hand gesture. In the next extract (10 min later), the director reminds the ensemble again to play the scene with a certain Haltung (line 2). This time, he first uses a gesture instead of a verbal expression to evoke the 'gambler attitude' (line 3): When trying again to introduce the gambler attitude, the director does not directly remind the ensemble (as in Ex. 3), but asks a question (line 2: 'what attitude would you have as' …), which is initially designed to be completed by the actors: After 'as', which projects an expression specifying the attitude, he leaves a pause (line 3), thus trying to elicit the kind of attitude from the actors (see Koshik, 2002). Since there is no uptake by the actors, he completes his utterance himself after a second's pause, but not through a verbal expression, but bodily through a posture/gesture (line 3; Fig. 10), which he obviously adopts from Ac2's mock implementations in the previous extract (see Figure 3 above). In this way, he avoids verbally labeling the attitude he demands from the actors (as he did in ex. 3). Instead, he uses a bodily form of expression that has the advantage of picking up on previous realizations by the actors (see ex. 3) and is also more directly connected to a physical realization than a verbal expression. D's attempt to elicit an embodiment of 'the gambler attitude' does not lead to a physical realization by the actors but is acknowledged by loud, sustained laughter (line 4) in which D himself joins in. With this, his rhetorical strategy to re-introduce the gambler attitude (lines 2, 3) is collectively constructed as a laughable and finally 'dissolved' by the director coming up with the verbal counter-part (line 6: 'as gambler'), again followed by collective laughter (lines 8, 9). While D is still laughing, the actors begin to produce mock implementations again (lines 4-10): Whereas Ac3 emulates D's posture including the rubbing hand gesture (Fig. 11), Ac2 plays a gambling addict and uses a somewhat different posture to do so (lines 10, 11; Fig. 12).
Since his attempt to introduce the gambler attitude is again treated in a non-serious way, the director now offers an alternative formulation (lines 11, 14, 16: 'or … so that it is somehow …. maybe challenge is…') and explicitly problematizes his concept of a gambler attitude (line 17: 'if you can't really do so much with gamblers'). As a result, a two-minute negotiation on possible alternatives follows (not part of the transcript) after which the director explicitly prompts the ensemble to do an attitude (line 161:'do an attitude/posture'). He uses the rubbing hand gesture in a toned-down way (Fig. 13) which, however, is not adopted by the ensemble. After a  short phase of re-orientation, the ensemble starts to play the scene without recognizably adopting the rubbing hand gesture (not part of the transcript).
In extract 4, D adopts a gesture originally produced by Ac2 (see extract 3) and uses the gesture as a projective cue to evoke his concept of the gambler attitude. 6 At the same time, the gesture is a part of the way the gambler attitude could be played. At this point, the posture/gesture is somewhere between a core element of actually doing or performing the gambler attitude and a sign (or a cue) for referring to or projecting it. Note that when the director instructs the ensemble to 'do a Haltung' (line 161), he does not refer to something conceptual or an attitude in the first place (of gambler/gambling) but to a posture which can be done ('do a …'), which he also demonstrates (Fig. 13). Interestingly, verbally he does not instruct a specific Haltung but just 'a Haltung' (line 161) and again he resorts to embodied means to concretize his verbal instruction, thus linking an abstract aesthetic concept to an embodied posture (see Sect. "Common ground and gestures in theater"). By instructing the ensemble this way, he demonstrates what he thinks is the 'correct Haltung' (as he refers to this Haltung later in Ex. 7).
In the next extract, two minutes later, the gambler attitude is not instructed by the director, but independently produced by one of the actors (line 1):  Mead (1934) has described projective cues as "significant gestures" allowing for anticipation, as such gestures are suitbale to "arouse in the individual the attitude which it arouses in others"(161), and, thus, begin to represent the whole joint action which they project.

Knowledge Accumulation in Theatre Rehearsals: The Emergence…
The ensemble is about to play the scene again, when Ac2 enacts the gambler attitude as a preparation for the imminent start of the scene play and again in a mocking way, not being taken seriously by his co-actors (line 1). This time and in contrast to the extracts before, Ac2 was not instructed to do so. Although he adopts the attitude to again ridicule D's idea, he offers, like before, a way of doing the gambler attitude, now including again the rubbing-hand-gesture (Fig. 14).
After a complaint of his co-actor (line 1), embodied signs of disapproval by Ac3 (line 1: raised eyebrows, head shake; later/line 5: covers her face with hands) and a prompt by the director to start (lines 2, 3), Ac2 justifies his behavior by referring to the gambler attitude (line 4.). D interrupts Ac2's explanation and treats it as redundant by producing what Ac2 is about to say in partial overlap (line 5: 'yeah yeah the gambler attitude'). Directly afterwards, he asks the ensemble to begin again (lines 6, 7), while Ac2 re-adopts a gambler attitude. In the performance that starts in line 29 again after two prompts by D to begin (lines 26, 27), Ac2 incorporates the rubbinghand-gesture into his performance (Fig. 15).
In extracts 3 and 4, the rubbing hand gesture has been mainly used to refer (metonymically) to and thus instructs the actors how to play the gambler attitude, often by D as illustration or embodied part of a bodily-syntactic gestalt (as in ex. 4, line 3 and line 161). In extract 5, the gesture is produced for the first time self-initiated as an integral part of performing the gambler attitude (by Ac2 in line 1), even though in a stylized version to make fun of it. Although Ac2 clearly quotes or depicts (Clark, 2016;Clark & Gerrig, 1990) the gambler attitude and the gesture, he also pretends to do it for its own sake when he justifies his mockery with 'this is the gambler attitude' (line 4). In any case, the gesture/gambler attitude is produced without being instructed, which is another step towards a routine. The fact that the gambler attitude is independently produced is a strong indicator for its acceptance and for its gradual establishment as shared knowledge between the participants. On the other hand, Ac2, who most actively adopts the gambler attitude, still shows distance and marks that it is not his own idea and not (yet) his own knowledge (a similar process is described in Deppermann & Schmidt 2021).

Using the Concept
This changes in the next two extracts from the last day of the rehearsals 10 days later. Doing the gambler attitude has become an accepted part of playing the scene. A larger part of the play has just been performed and the director reviews problematic parts: The main point of criticism in the selected fragment is the 'connections' 7 (line 3). In his critique to produce the connections more accurately (lines 8-13), he parenthetically embeds a positive evaluation of the gambler attitude (line 7). At this late point in the rehearsal process, the concept can easily be used to evaluate the previous performance. In terms of IRE-sequences (Mehan, 1979), the gambler attitude appears in the evaluation slot (third position), after the scene has been played. In the extracts before (3-5), the gambler attitude was mentioned by the director before playing a scene in an initial slot (first position) as part of his instruction. The concept is not instructed or explained, nor is it contested or negotiated anymore; rather it has been conducted self-initiatively as a routine part of performing the scene. Moreover, the director can refer to a part of the scene in retrospect as having been played in 'the gambler attitude' (line 7). Obviously, the accumulation of shared knowledge changes the way interaction sequences are realized and what action can be performed.
Another indicator for its gradual transition into a stock of common knowledge is that the gambler attitude is mentioned only en passant, placed between the criticism about accuracy (line 7 in between lines 1-2 and 9-13), which is topically in focus. In this way, the director treats performing the gambler attitude as something that was naturally expected (line 7: 'what is good is the energy of the gambler attitude').
The rubbing hand gesture is neither mentioned verbally nor demonstratively performed to refer to the gambler attitude (as in Ex. 1), rather it appears as an integral gestural element of illustrating the gambler attitude within D's composite utterance in line 6 (Fig. 16).
Obviously, the gambler attitude has become an established term, a 'thing' to which one can nominally refer and which produces its own 'effects' (here: 'energy'). This is even more obvious in our last fragment (Ex. 7), ten minutes later. Just before, the participants had discovered a tension between the tempo in which the text lines are produced and the basic attitude ('the gambler attitude') with which the scene should be played. To produce the text lines in an accurate way, a moderate tempo is required; playing the scene with the gambler attitude, in contrast, tempts them At this point, the kind of attitude is not even specified anymore but simply treated as 'the correct attitude' (line 67), which presupposes its accepted normative-deontic status. By separating two aspects of playing the scene, 'the tempo' (line 66) and 'the attitude' (line 67), the director treats the gambler attitude as a component that could be removed or added in the practicing of the scene. By this, it is reified as a fixed and reproducible 'thing'.
We now have reconstructed the interactional history of a gesture over seven instances and, as shown in extract 1, the instruction of the director is totally clear at the end of the process. The director wants the ensemble to play the scene with the gambler attitude as an additional component. What this component consists of is referred to and at the same time embodied by the rubbing-hand-gesture. As seen, everybody is able to follow his instruction.

Summarizing Discussion
In this study, we reconstructed the process in which professional actors and a director develop shared knowledge in repeated rehearsals of the same scene. To make this process of knowledge accumulation traceable, we have focused on a process of establishing a concept of an attitude ('the gambler attitude') and finding an embodied solution (of which 'the rubbing hand gesture' is a part), which, at the time, was used to symbolize and project that attitude. On the one hand, we identified interactional practices by means of which the participants build shared knowledge about a particular concept and showed how through such an accumulation of knowledge interactional practices change. On the other hand, we have seen how a particular gesture emerged within this process and how it is used to develop a staging of the scene. These two processes are intertwined, and in this case, the close relation between concept ('gambler attitude') and gesture ('rubbing hand gesture') is mediated by the notion of Haltung (see Sect. "Common ground and gestures in theater"). By tracing the chronological order of rehearsing a particular scene, we have shown that changes of instructional activity rest on the accumulation of knowledge within this activity. At the same time, it became clear how the investigated gesture emerges through a process of increasing stabilization based on its highly variable but continuous use and its mutual imitation and adaption. The grounding process begins with the development of a rough idea of what this scene could be about, namely 'the gambler attitude'. The longitudinal process of developing this idea into an embodied performance can be distinguished in three steps, namely a) introducing the concept, b) developing and adopting the concept through the production of an embodied solution ("the gesture") and c) using the concept and the gesture.

Introducing the Concept
When introducing the concept, the director specifies a Haltung for how to play the scene, which he derives from the script. The roots of its creation lie in the textual basis of the play and its prior thorough interpretation by the director. On the one hand, the concept is elaborated and equipped with different layers of meaning (e.g. competitors; disturbance; nervous; possible performative aspects: taking the text from one another etc.). On the other hand, the concept is given a unique verbal expression early on (Ex. 2, line 45). Establishing a label, Spielerhaltung; 'gambler attitude', makes it possible to refer to it later and to accumulate knowledge compiled so far under an umbrella term (on the significance of labels in rehearsals cf. Norrthon, 2021). Although it is in no way clear how the concept is to be implemented bodily and whether it will be viable, the director can now refer to it in further rehearsals and work with it, in which the goal is to decide on an embodied solution for playing the attitude.

Developing and Adopting the Concept Through the Production of an Embodied Solution ('The Gesture')
The Haltung provides the participants with a certain stereotype (e.g. a gambler) and derivable typical patterns of both attitude and embodied behaviour (e.g. being nervous/addicted, rubbing one's hands etc.). 8 In the beginning, neither the concept of 'gambler attitude' nor the 'rubbing hand gesture' has a reality for the participants. During the process of developing and adopting the concept, the concept is extensively negotiated, challenged through mocking and by that kept flexible for a long time. This process is primarily conveyed by bodily enactments and trying out implementations and not by defining, explaining and arguing about its meaning. Its intermediate state between something completely new and something already acquired is indexed by the way the participants treat the concept in interaction: • The concept is explicitly instructed at the outset of rehearsing a scene (instead of being simply executed; Ex 2, 3, 4); • The concept must be explicitly recalled (Ex. 3), which treats the concept as known but not yet routinized; • The concept is explicitly named, but indexed as shared knowledge by using definite/ demonstrative articles (e.g. Ex. 1/ line 45: 'this gambler attitude'; Ex. 3); • Instructions to implement the concept are not just implemented but questioned and negotiated (Ex. 3), so that the concept is temporarily up for disposition and alternatives are discussed (mainly in Ex. 4).
While the gambler attitude is explicitly introduced, the 'rubbing hand gesture' emerges without being openly explained, instructed or named. The gesture is not treated openly as a 'learnable' and was not taught but emerged within iterations of rehearsing the same scene. In our case, the concept (gambler attitude) constrained certain ways of embodiment (as e.g. a 'rubbing hand gesture'), whose various realizations helped to stabilize the concept. 9 These implementations during the phase of acquisition also show that the concept has long been in the state of a not-yet-accepted component of performance: • The concept is implemented mockingly, which on the one hand creates concrete physical representations, but at the same time indicates distance; • The implementations developed so far are treated as still open for negotiation (D explicitly prompts the actors to 'do a Haltung') and at the same time as somewhat determined (D demonstrates Haltung bodily by using the 'rubbing hand gesture') (Ex. 4, line 161); • The concept and the gesture are partly carried out in a self-initiated way and thereby adopted (Ex. 3, 4).
The gesture itself emerges in a process of mutual imitation and adaption, which goes through the following steps: 1. Pantomime (Ex.3): the gesture is first produced by Ac2 as a by-product of a holistic pantomimic depiction, including a little narrative scenario (a gambler at a slot machine). At this stage a variety of possible implementations are offered and the embodiment of the concept is very variable and not yet determined. Especially the mocking realizations narrow down the possible meaning of the concept to gambling addiction, to the representation of which the gesture contributes significantly. Here, the gesture appears in various forms, which are made recognizable as different realizations of the same idea by the common feature of the nervous rubbing of the hands/fingers.

Mutual emulation / adoption of the pantomime and the gesture (Ex. 4): D emulates
Ac2's (mocking) pantomime to instruct the ensemble to play the scene with the gambler attitude, thereby also adopting the gesture previously produced by Ac2. His adoption of the gesture is in turn emulated by two of the actors and partially adopted in the subsequent performance. This shows how each further realization reflexively builds on the previous ones. Although neither the gambler attitude nor the gesture are yet accepted parts of the performance, the collaborative process of increasing stylization of Ac2's originally pantomimic "proposal" (Löfgren & Hofstetter, 2021:1) establishes the gesture more and more as a way to refer to the gambler attitude. 10 3. The gesture as both a way of referring to and performing the gambler attitude (Ex. 4): When the director explicitly instructs the ensemble to 'do a Haltung', he uses the gesture both to refer to the gambler attitude and to show in a stylized way how 'a Haltung' could/should be enacted. Interestingly, the status of the concept as not-yet-routinized is reflected in a split of multimodal resources. While he uses verbal resources to indicate that the process of finding a Haltung is still open, he deploys embodied/gestural means to suggest a certain choice.

Using the Concept and the Gesture
In the end of the rehearsal process, knowledge of the concept is presupposed. Implementations no longer need to be instructed or negotiated, but are expected to be simply performed; in turn, comments about the concept can appear both as evaluations after (as in Ex. 6, 7) and as instructional cues (as in Ex. 1) before a scene is played. The concept is treated normatively as the only accepted way to play the scene (referred to as 'the correct Haltung' in Ex. 7). The concept is mainly used to conduct and to evaluate the performance (Ex. 6/7). It and its forms of realization have become a part of the ensemble's "professional vision" (Goodwin, 1994). Furthermore, it is reified as something that can be added and omitted like a 'thing' (Ex. 7). If it is still referred to at all, it is often replaced by implicit forms of reference ('the correct attitude' in Ex. 7; no verbal reference, but only a stylized gesture in Ex. 1). The gesture appears either as an uninstructed integral part of the performance or as a means of gestural reference to the concept (Ex. 1). Finally, the knowledge of the gambler attitude conveyed throughout the rehearsal process is packaged in this ad hoc, accidental, and collaborative emerged gesture, which is finally sufficient to actualize a whole complex of specific knowledge required for adequate acting (the 'correct concept' to play the scene, its embodiment and 'the rules' for its usage). During this appropriation process, the practices for managing this process have also gradually changed: • Instructions concerning the concept get shorter and disappear in the end completely (corresponds to findings in Deppermann, 2018). Similarly, negotiations decrease (s.a. Schmidt & Deppermann in this volume); • References are getting more and more implicit (in Ex. 1 they are not even verbal anymore); • The concept is more and more defocused (in terms of informational structure) and, by this, reflexively indexed as shared knowledge (Ex. 6/7); • The sequence structure is inverted from using the concept in initial actions (first position) to its usage in an evaluative position (third position).
The accumulation of knowledge in theater obviously relies on the body as an instrument, both for the exploration and development of the performance and for its execution. Our gesture derives from a holistic depiction (pantomime) of a concept (mimicking a gambling addict playing with a slot machine). Its subsequent use as a 'sign' for referring to a (certain way of embodying a) concept thus has its roots in a situated activity ('gambling'). Unlike abstract concepts (such as the gambler attitude), the evocation of a situated activity links abstract concepts to experience-based action knowledge (Lutterbie, 2010, Streeck, 2013. Our gesture apparently serves both as a tool and a target in a 'laboratory' process in which the ensemble explores various embodied resources for performing the scene. In the process of trying things out and deciding on particular embodied actions to use in the performance, meaning is created -not only for a subsequent audience, but primarily within the rehearsals process for the participants themselves. Seen in this light, our gesture, and presumably gesture in theater generally, seem to serve as a bridge between the tensions of abstract, verbal concepts ('knowing what') and embodied, action-based realizations of these concepts ('knowing how') (Ryle, 1949).