Simultaneously performing several activities is a phenomenon we encounter not only in everyday life but also in many professional situations. This Ph.D. project describes the conditions under which people can perform several activities simultaneously. For this purpose, a system of structural compatibility of multimodal resources is developed on the basis of 43 qualitative individual case analyses. The data basis is provided by a corpus of 200 h of a theater rehearsal process recorded with video cameras and mobile eye-tracking glasses. The analyses revealed that humans require certain structural conditions to perform more than one activity simultaneously. Performing multiple activities at the same time is possible if participants can divide multimodal resources among the activities (structural compatibility). If two activities require the same resource (e.g., gaze), they are structurally incompatible, and one of the activities can be paused or canceled until the required resource is available again. However, if a situation requires that several activities be realized simultaneously despite structural incompatibility, the lack of a resource can be briefly compensated through the help of interactional procedures, e.g., routinization, prioritization, and synchronization.

The pager vibrates, and the senior physician rushes to the patient - cardiac arrest! Two residents and an anesthesiologist she has never seen before arrive with her. “Prepare everything for cardiopulmonary resuscitation,” she calls. She routinely puts the ventilation mask over the patient‘s mouth and nose. At the same time, she calls: “Chest compression; 30-to-2.” The doctor nods briefly and begins chest compressions. Now she has to concentrate and pay close attention to repeatedly pumping air into the patient‘s lungs twice with the resuscitator after the doctor compresses the patient‘s chest 30 times. At that exact moment, the anesthesiologist asks which tube she should prepare. The team leader turns to the anesthesiologist and points to the object she is looking for: the one there in the drawer, of course! When the team leader turns back to the patient, she has missed the moment to ventilate. The oxygen level in the patient drops... This example is based on a training case described by Pitsch/Krug/Cleff (2020) . It demonstrates that there are processes that can be easily reconciled, whereas other processes can lead to problems if they are performed at the same time. What are the conditions under which a person can perform two or more activities simultaneously? What needs to be changed so that communicative problems (such as in the example above) do not occur or occur as infrequently as possible?

The concept of multitasking, which is prominent in society, seems to provide an answer to these questions. In everyday understanding, it describes the ability of an individual to manage two or even more tasks simultaneously. As a psychological concept, however, multitasking focuses primarily on cognitive tasks and problems that arise when two processes are mentally incompatible. In examining the example, it is questionable whether the team leader was really cognitively unable to answer the question and perform ventilation at the same time. Rather, the problem seems to be that the two activities require different attention spans and hand grips; the two activities are not cognitively incompatible but structurally incompatible in terms of coordinating with the anesthetist. If one expands one‘s view from the rather individualistic psychological concept of multitasking to the interactional concept of multiactivity in (social) interaction research (Haddington et al. 2014) , one realizes many situations in which people engage in several activities simultaneously. For instance, when people have conversations while eating dinner together (Egbert 1997) , when a group mucks out (i.e., cleans up) a sheep stable together (Keevallik 2018) , or when a person consults another on how to proceed while building a closet (Krafft/Dausendschön-Gay 2007) . Looking at these everyday situations in terms of interactions rather than psychology raises the question: Under what conditions can two or more activities be completed simultaneously, and when is it difficult to do so?

So, what are the structural conditions of concurrent activities? To investigate this question, it is useful to compare several cases. For this purpose, settings in which a fixed group of people comes together in repeatedly similar situations lend themselves well, for example, during theater rehearsals. For this reason, in my Ph.D. project, I set up several cameras in a rehearsal room and audio- visually recorded all 31 rehearsals of a professional theater production company in Germany from different perspectives ( Krug/Heuser 2018, Krug 2018 ). In this way, I captured every situation in which the participants performed multiple activities simultaneously; in total, I qualitatively compared 43 cases.

But how can one determine when it is "difficult" or "easy" for interactors to coordinate several activities simultaneously? This is only possible when the researcher comes down from his/her “ivory tower" to eye level with the participants because, as humans, we cannot see into the minds of others and are dependent on their (body) language to confirm their understanding of an action. Thus, it only becomes clear that my interaction partner has understood my wave as a greeting when, for example, he/she also waves back. This participant perspective is central to conversation analysis ( Schegloff 2007 ). Working with the means of conversation analysis is to scrutinize the reciprocated actions realized by others during an interaction. In this manner, the coordination of actions ( Deppermann 2014 ) reveals how and under which conditions interactants break off or pause one activity in favor of another.

Figure 1: The actor interrupts his smartphone activity in favor of the greeting.

The example in Figure 1 illustrates how something like this can unfold. In it, an actor surfs the Internet on his smartphone at the beginning of a theater rehearsal (image 1). He continues to do so even when the dramaturge of the production enters the stage and wishes the actor a good day (“gu_n TACH“). Without looking up, the actor reciprocates this greeting with a hello (“ MOIN moin“) (image 2). Here, the actor can coordinate his two activities of internet surfing and greeting in such a way that he can perform them at the same time. This is possible because he does not look at his conversation partner during the verbal greeting but keeps his gaze (as a visual resource) directed at the smartphone. The actor implements the Internet surfing activity here by holding the smartphone with one hand and controlling it with his thumb. From this observation, which seems trivial at first glance, one can deduce an important prerequisite for the simultaneous performance of several activities: the body‘s processes (the so- called multimodal resources) must not interfere with each other when they are used for different activities. They must be structurally compatible with each other. Unlike chameleons, which are able to look in different directions, humans can anatomically select only one gaze target at a time. Thus, in order to realize the greeting at the same time as surfing the Internet, the actor coordinates the activities in such a way that he uses his gaze (visual resource) and his hand (haptic

resource) for surfing and only participates in the greeting via speech (verbal resource). By splitting the resources between the activities in this way, the actor is able to perform both activities simultaneously.

This only changes when the dramaturge expands the greeting with well? (“na?“). The actor responds by turning his gaze from the smartphone, looking at the dramaturge, and also responding with na? (‘well‘?) (image 3). Thus, the actor still keeps his hand on the smartphone but now has his gaze focused on the greeting in addition to his speech. With this division of bodily resources, it is not possible for him to continue surfing on the smartphone: his activities here are structurally incompatible with each other. However, since he continues to hold the smartphone, he indicates to the dramaturge (and all other participants) that he will probably continue his surfing activity as soon as his visual resource becomes available again. This behavior is a continuation projection. This phenomenon regularly occurs when people do two things at the same time but need the same resource (e.g., gaze) for both. People then pause one activity, here web browsing, in favor of another (e.g., a greeting). Such continuation projections of paused activities always involve some kind of "freezing" a currently ongoing process, for example, holding a cup just in front of the mouth while speaking (cf. Hoey 2018) . Since the dramaturge expands his greeting once again with the question, “ How are you?” (“ Wie geht‘s dir?“) and also offers his hand to the actor (image 4), the greeting now requires the actor‘s haptic resource in addition to his verbal and visual ones: he can now no longer hold the smartphone with his right hand and decides to let it slide onto the table and join in the hand greeting. Thus, no physical resource now remains in the surfing activity. It is treated as aborted by the interactants. In my data, it appears that aborted activities are more difficult for interactants to resume, which is why participants try to pause activities rather than abort them. The example shows that participants can simultaneously coordinate two simultaneously occurring activities if they use the resources in a structurally compatible way. If activities behave in a structurally incompatible way, they are paused or aborted depending on the degree of incompatibility.

What can participants do when a situation requires that two structurally incompatible activities not be aborted or paused but completed simultaneously, for example, during resuscitation as in the introductory example?

Such situations can be observed regularly in theater rehearsals when scenes are being rehearsed. In order not to have to start from the beginning with every forgotten word, one of the participants prompts. This means that if an actor/actress is stuck in the text (so called blanking ), the prompter recites the correct play text. This requires the prompter to read the actors‘ performance in the script. How does a prompter recognize that an actor is blanking? In the analyses, two regular features emerge in this regard. First, actors often pause before blankings. However, it is not uncommon in the theater to intentionally insert dramatic pauses to intensify the play. Thus, secondly, in order to distinguish a dramatic pause from a blanking, the prompter must observe the performance. Since she can only either observe the play or read along in the script, the two activities are structurally incompatible with each other. Both activities, observing and reading along, require the gaze as a visual resource. How does a prompting person manage to observe the performance and simultaneously read-along, despite this structural incompatibility? To determine this, one must record the gaze of the prompter. This is achieved via so-called mobile eye-tracking glasses, which record the view of the person wearing them. A colored circular ring shows where the person is looking from a subjective perspective.

Figure 2: The assistant director prompts the actor. Image 1 shows the perspective of a camera behind the director's table. Images 2-4 are taken from the eye-tracking glasses of the assistant director.

The example in Figure 2 shows the prompter‘s gaze behavior and demonstrates the compensation practices with which the prompter (left in image 1) deals with the structural incompatibility of the activities of observing and reading along. In doing so, she reads the script while the actor (right in image 1) acts out the scene on stage (image 1). By analyzing the prompter’s eye-tracking data (images 2–4), we see that she forms a kind of grid with her hands in order not to lose her place in the script (image 2) and reads what the actor says in the script. Suddenly, the actor first pauses for 0.4 s, and then utters a stretched delay signal, äh . Since this is an element that is not recorded in the script, the prompter looks up at the actor (image 3). Here she can observe that the actor is frozen in his play and has stopped moving. She interprets this not as a dramatic pause but as a situation in which the actor is stuck in the text. Since this must be avoided, she then recites the missing text (“Ich steh immer noch regungslos da“). The blanking is overcome when the actor picks up the text and integrates it into his performance (image 4). At this moment, the prompter re-lowers her gaze into the script. As the red eye-tracking circle ring shows, her gaze lands unerringly on her pencil as part of the grid. This helps her to quickly resume her read-along activity without having to search for the right line.

As this reconstruction of events shows, it is by no means the case that the prompter can completely resolve the structural incompatibility of the activities of observing and reading along; she can still either look at the actor or read the script. However, she resorts to practices that compensate for the absence of the visual resource, at least for a short time. For example, she reads along in the script until she gets a clue about a text blanking. In all cases studied, these cues consist of the pattern pause in speech and stretched delay signal. What is exciting about this is that it is neither a prearranged cue nor something that actors learn in their training. Instead, this is an interactional negotiation. The prompter only redirects her attention from the script to the actor when there is a concrete indication of a blanking. If the actor blanks, she verbalizes what has just been read. This means that the prompter not only reads along, anticipating the words, but is also able to repeat an entire sentence while looking at the actor. In this way, what is read along is made available in the observation. Since the prompter immediately resumes her read-along as the actor continues in the text, she minimizes her time not doing so. Accordingly, the coordinative action of the prompter is characterized by three procedures: a) routinization, b) synchronization, and c) prioritization. a) Routinization: With the help of the script, she can predict the course of the scene and the future utterances of the actors, which enables her to read along in anticipation. b) Synchronization: While reading along with the performance, she looks at the parts of the text where the actor could potentially blank. c) Prioritization: She withdraws her visual resource from one activity for a minimally short moment only when there is a need for action in the other activity. Through these procedures, the prompter naturally does not manage to grow a second pair of eyes or learns to gaze like a chameleon; however, she can compensate for the absence of the visual resource in such a way that none of the simultaneously relevant activities has to be interrupted or paused.

The analyses show that we need certain structural conditions to perform more than one activity simultaneously. Performing more than one activity at the same time is possible if we can divide our physical resources among the activities (structural compatibility). If two activities require the same resource (for example, the visual resource gaze) to perform, they are structurally incompatible. In such instances, one of the activities can be canceled or paused until the resource is available again. If, however, a situation requires that several activities be realized simultaneously despite structural incompatibility, the lack of a resource can be compensated for briefly with the help of the interactional procedures—routinization, prioritization, and synchronization. This phenomenon is called "multiactivity." As the example of the prompter demonstrates, it is essential that she have recourse to these techniques in order to be able to pursue her task. Accordingly, the question arises as to whether this knowledge is limited to prompter situations or whether there are no other areas of application. In artistic fields, the simultaneity of several activities always plays an important role when something is elaborated while it is being done. In the elaboration of scenes (Krug 2020a) , something is performed while it can be commented on and, thus, changed at the same time (Krug 2020b) . The simultaneity of activities is here the structural precondition for creative work. Furthermore, this applies to many didactic areas: in dance lessons, a dance can be demonstrated and explained at the same time; in vocational inductions, a machine can be operated, and its functioning explained at the same time; and in school, an experiment can be demonstrated, and the physical laws behind it explained. In all these examples, the simultaneity of activities is understood as an opportunity to communicate complex relationships. But what happens when the simultaneous occurrence of activities in a situation poses a problem? We could clearly see this in the initial example of the resuscitation situation: here, physicians have to perform several activities simultaneously, which, on the one hand, are highly time-critical but, on the other hand, are not always compatible with each other. As recent studies have shown, annually, only 10% of the approximately 700,000 people who suffer cardiac arrest in Europe survive resuscitation (Gräsner et al. 2014) . Some of these failed resuscitation attempts are due to problems in team communication (Castelao et al. 2013) . An initial study by Pitsch/Krug/Cleff (2020) shows that some of these problems occur when team leaders instruct their team while simultaneously performing an often-complex medical intervention. Since the activities are often structurally incompatible, the team leader faces a dilemma: should she instruct her team on the next steps, which ensures the continuation of resuscitation, but thereby risk suspending the patient‘s ventilation for a short period of time, which could result in hypoxia and thus permanent damage? In the worst case, the team leader tries to meet both requirements and fails twice: an improperly instructed team can prepare resuscitation measures poorly, and a failure to treat the patient can have fatal consequences. Using the model of structural compatibility presented here, such communicative problems can be systematically identified, described, and dealt with. Particularly, the model can support medical (and other) professionals in distributing tasks in such a way that only compatible activities have to be realized at the same time. The model thus provides, for example, a structural argument for the fact that team leaders should, if possible, not perform any medical hand movements but should concentrate only on their managerial activities. Hopefully, this knowledge of the structural compatibility of activities, which can be well trained in medical facilities, will contribute to save more lives in the future.

• March to April 2016: audiovisual data collection at the theater • April to June 2016: Data preparation (synchronization, documentation, export) • September 2016: Presentation of first results at the GAL Congress in Koblenz ("Prompting in Theater Rehearsals. Co- construction of play actions through multiactivity"). • December 2016: Analysis and discussion of the data at RWTH Aachen University under the direction of Marvin Wassermann ("Undressing in Interactions. Multimodal coordinations of multiple activities at the ‘edge‘ of theater rehearsals"). • April 2017: Data session at the workshop Seeing and Noticing - Videoanalysis in Action (V), Genres, Forms and Structural Levels in Bayreuth ("Rehearsing in Theater Rehearsals as a Communicative Genre?"). • June 2017: Presentation at the ICMC in Osnabrück ("Rehearsing in theatre: Collectively achieving an interactional system by coordinating multiple activities"). • July 2017: discussion of eye-tracking data in interactions at IPrA in Belfast ("Eye-tracking in theater: coordinating multiple activities during a theater rehearsal"). • November 2017: Start to work on a special issue on instructions in theater and orchestra rehearsals together with Axel Schmidt, Monika Messner and Anna Wessel. • Juli 2018: Reflection on data collection at ICCA in Loughborough ("Collecting Audio-Visual Data of Theatre Rehearsals. (Non- )Intrusive Practices of Preparing Mobile Eye-Tracking Glasses during Ongoing Workplace Interactions") • September 2018: publication on how much my data collection disrupted the rehearsal process in Krug, Maximilian & Heuser, Svenja (2018): Ethics in the field: research practices in audiovisual studies. In Forum Qualitative Sozialforschung / Forum: Qualitative Social Research, 19(3), art. 8. • September 2018: Joint performance with Anna Wessel at the GAL Poster Slam in Essen wins the GAL Poster Award. • January 2019: Start of collaborative work with Anna Wessel on repetition in theater rehearsals as part of the workshop Linguistic- communicative practices in the environment of art institutions. Multimodal and -medial perspectives on public communication at Justus Liebig University Giessen ("Practices of Repetition in Theater Rehearsals"). • January 2020: Submission of dissertation • August 2020: Defense of the dissertation (summa cum laude) • November 2020: Publication of Krug, Maximilian (2020): Erzählen inszenieren. Ein Theatermonolog als multimodale Leistung des Interaktionsensembles auf der Probebühne. In: Linguistik online 104 (4), S. 59–81. • December 2020: Completion of work on the special issue on Instructions in theater and orchestra rehearsals together with Axel Schmidt, Monika Messner and Anna Wessel. Included among others: o Krug, Maximilian; Messner, Monika; Schmidt, Axel; Wessel, Anna (2020): Instruktionen in Theater- und Orchesterproben: Zur Einleitung in dieses Themenheft. In: Gesprächsforschung Online 21, 155-189 o Krug, Maximilian; Schmidt, Axel (2020): Zwischenfazit: Sukzessive und simultane Verzahnung von Spiel- und Besprechungsaktivitäten – eine Instruktionsmatrix für Proben. In: Gesprächsforschung Online 21, 264-277 o Krug, Maximilian (2020): Regieanweisungen "on the fly". Koordination von Instruktionen und szenischem Spiel in Theaterproben. In: Gesprächsforschung Online 21, 238-267 • February 2022: Publication of the dissertation. Open Access!

Krug, Maximilian (2022): Simultaneity in interaction. Structural (In)Compatibility in Multiactivities during Theater Rehearsals. De Gruyter. DOI (peer reviewed)

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