Mental Representation of Spatial Movement Parameters in Dance

Spatial Cognition & Computation, 12:111–132, 2012 Copyright © Taylor & Francis Group, LLC ISSN: 1387-5868 print/1542-7633 online DOI: 10.1080/13875868.2011.626095

Mental Representation of Spatial Movement Parameters in Dance Bettina Bläsing1 and Thomas Schack1 1 Neurocognition

and Action Research Group & Center of Excellence Cognitive Interaction Technology (CITEC), Bielefeld University, Bielefeld, Germany

Abstract: Via training, dance experts develop special experience-based embodied representations of body and movement. Professional dancers, amateurs and novices sorted central functional nodes of two dance movements according to their spatial equivalence. Results of a hierarchical cluster analysis and classification probabilities revealed movement-specific differences in mental representations related to skilllevel. Cluster solutions of experts reflected functional structures, with adequate spatial parameters associated to the main movement phases. Amateurs achieved similar results only for the less complex movement, whereas novices showed nonfunctional results. The findings suggest that only dance experts’ distinct embodied representations of dance movements include information about body-centered spatial parameters. Keywords: dance expertise, mental representation, movement concepts, spatial parameters, motor imagery

1. INTRODUCTION Dance expertise has recently become an increasing field of study among cognitive and neuroscientists (see Bläsing, Puttke, & Schack, 2010). There are several aspects of dance expertise that make this field worthwhile for those interested in action-perception coupling and movement expertise. Orientation in space is one of the crucial cognitive skills required in dance, and it has been suggested that spatial awareness, body representation and perception of time are the main cognitive abilities in which dancers are trained (Jola, 2010). Even though dancers are not specifically skilled in spatial tasks in general (Jola & Mast, 2005), evidence exists that dancers have a more accurate position sense based on proprioceptive information than non-dancers, and that dance Correspondence concerning this article should be addressed to Bettina Bläsing, Neurocognition and Action Research Group & Center of Excellence Cognitive Interaction Technology (CITEC), Bielefeld University, PB 100131, 33501 Bielefeld, Germany. E-mail: [email protected] 111

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training can increase the relative influence of proprioception on multimodal integration (Jola, Davis, & Haggard, 2011). Movement learning and memory are other domains dance experts are particularly skilled in, as there is hardly any other movement discipline in which the learning of complex novel movement patterns plays such a crucial role. As a consequence, dancers’ memory for movement has been investigated by many authors (e.g., Cross, Hamilton, Kraemer, Kelley, & Grafton, 2009; Opacic, Stevens, & Tillmann, 2009; Stevens, Ginsborg, & Lester, 2011). Based on their rich repertoire of movements and body configurations stored in long-term memory, dancers are better than nondancers at anticipating visually presented dance movements, they can remember movements for a longer time than novices (Smyth & Pendelton, 1994) and are especially good at recalling choreographically structured sequences (Starkes, Deakin, Lindley, & Crisp, 1987). Allard and Starkes (1991) emphasized the importance of skilled memory in dance experts, mentioning that dancers use unique memory techniques to encode movement sequences, such as marking body movements with the hands or using motor imagery (Golomer, Bouillette, Mertz, & Keller, 2008). For dancers, mental representations in long-term memory provide a vital basis for learning novel movement sequences and for adapting and refining movements corresponding to aesthetic and expressive requirements (see Bläsing, 2010). Such cognitive movement representations are based on spatial and temporal features of movement concepts that are acquired during training and repeated movement performance (see Schack, 2010). Dance expertise arises due to an optimised cooperation of cognitive control and sensorimotor processing. There is much evidence that the cognitive side of motor expertise is characterised by hierarchical networks of concepts (Ericsson & Smith, 1991), and that highly versatile human movements are built up from individual movement segments in a modular way (e.g., Flash & Hochner, 2005; Schack & Ritter, 2009). In classical dance, the modular and hierarchical structure of complex movements is clearly reflected by a movement repertoire that is in itself modular and hierarchical, which is reflected by its specific movement vocabulary and grammar. Human movements in general have been described as being based on a hierarchical structure of cognitive and motor-driven building blocks (see Ericsson, 2003; Schack, 2004; Rosenbaum, Cohen, Jax, Van Der Wel & Weiss, 2007). Schack’s architecture model (Schack, 2004; Schack & Ritter, 2009) postulates four levels of action control: a level of sensorimotor control providing an interface to sensors and effectors, two intermediate levels of sensorimotor (effect) representations and mental representations, accommodating basic action units at different levels of abstraction, and a topmost level of mental control shaping purposeful behavior. According to this model, Basic Action Concepts (BACs) are major representation units for complex movements on the level of mental representations. They tie together functional and sensory features. Their functional

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features are derived from movement goals; this connects BACs to the level of mental control. BACs also integrate sensory features of submovements through chunking, and thereby refer to the perceptual effects of the movement. This connects BACs with sensorimotor representations and perceptual effects. Finally, the connection between BACs and sensory effect representations permits the intentional manipulation of the cognitive framing conditions of sensorimotor coordination. BACs do not refer to behavior-related invariance properties of objects as this is the case in object concepts, but to perception-linked invariance properties of movements. Results from different lines of research suggest that such movement representations might provide the basis for action implementation and action control in skilled voluntary movements in the form of cognitive reference structures (Schack, 2009; Schack & Mechsner, 2006; Schack & Ritter, 2009). The internal structure of such representations is related to the quality of movement execution. The higher the degree of order formation in long-term memory, the better a dancer can perform a movement, and the less attention and concentration are needed for excellent performance. The approach we take here is to investigate cognitive movement expertise by analysing the structure of such networks of movement knowledge in our participants’ long-term memory. The aim of the present study was to investigate cognitive representations of dance movements in long-term memory, with a focus on spatial parameters in an egocentric frame of reference. Cognitive movement structures of two different basic ballet movements, the Petit pas assemblé and the Pirouette en dehors, of three groups of participants varying in dance expertise were measured and compared to each other. To enable the elicitation of mental structures underlying movement production in ballet, the Structure Dimensional Analysis-Motorics (SDA-M, Lander, 1991; Lander & Lange, 1996; Schack, 2004) method was applied to measure the structure of knowledge representations based on spatial features psychometrically. The SDA-M has previously been applied to analyze mental representations of complex movements in dance (Bläsing, Tenenbaum, & Schack, 2009), different kinds of sports (e.g., Schack, 2004; Schack & Mechsner, 2006), manual action (Schack & Ritter, 2009) and rehabilitation (Braun, Beurskens, Schack, Marcellis, Oti, Schols, & Wade, 2007). In these studies, a direct scaling of building blocks of movement (i.e., BACs) was applied to analyse performance-based mental movement representations in memory. Bläsing, Tenenbaum, & Schack (2009) used the same material (i.e., the Petit pas assemblé and the Pirouette en dehors with their respective sets of BACs) to examine representation structures in long-term memory of dance experts, amateurs (advanced and beginners) and novices via SDA-M with direct scaling. In this setup, participants had made direct judgements about the functional equivalence of pairs of BACs (BAC BAC: pairs of BACs had to be judged as closely or not closely related to each other).

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In contrast, in the current study an indirect scaling via decisions concerning the functional relationship of BACs and spatial features was used (BAC features: BACs have to be judged as closely or not closely associated to given spatial features). Both methods include a hierarchical cluster analysis that reveals clusters of BACs displayed as dendrograms; the difference is that in indirect scaling features are predefined, whereas the concept dimensions in direct scaling are accessed via a factor analysis. The indirect scaling method via SDA-M has only been applied in one study so far, in which the mental representation of the front loop in wind-surfing based on its spatial, temporal and force parameters was examined in experts and novices (Schack, 2010). Based on the results of the previous study (Bläsing, Tenenbaum, & Schack, 2009) and the consideration that dancers are especially trained in spatial orientation and memory tasks, the aim of the current study was to explore mental representations of movements based on their association to spatial parameters in the long-term memory of dancers who vary in expertise.

2. METHOD 2.1. Participants Three groups of different expertise participated in our study. The group of experts (Pas assemblé: N D 15, 8 women, age: 18–36 .26:13 ˙ 5:29/ years, 7–20 .14:6 ˙ 4:22/ years of training; Pirouette: N D 17, 10 women, age: 18–40 .26:44 ˙ 6:76/ years, 7–35 .16:75 ˙ 6:86/ years of training) included trained dancers who had received professional training in classical dance and were active members of professional classical or modern dance companies at the time of the study. The group of amateurs (N D 18, 15 women, age: 16–45 .29:44 ˙ 6:89/ years, 1–20 .8:22 ˙ 7:22/ years of training) included individuals who had trained classical dance mostly on a non-professional level. The group of novices (N D 19, 13 women, age: 22–35 .26:0 ˙ 3:42/ years) consisted of sport students who had not trained classical, modern or jazz dance, but had mainly concentrated on soccer, volleyball, basketball or track-and-field. All participants gave their informed consent prior to their inclusion in the study; no financial or course credit reward was given for the participation in this study. The study was performed in accordance with the ethical standards of the 1964 Declaration of Helsinki. 2.2. Movement Tasks We chose the Petit pas assemblé and the Pirouette en dehors from the fourth position because of their high degree of familiarity among professional and amateur dancers and their ubiquity even in beginners’ classes. Both movements belong to the basic movement repertoire of classical dance (see


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Vaganova, 2002), both movements show a sufficient degree of complexity, but otherwise they differ essentially in nature. The Petit pas assemblé (see Figure 1) is a small jump that is commonly performed at quick pace within a sequence of small jumps and steps. It starts with plié (bending the knees) and sideward sliding of one foot; followed by a small jump during which the stretched legs meet in the air before landing. The Pirouette en dehors (see Figure 2) is a rotational movement that requires highly defined coordination and constant adjustment of the body axis in order to be performed correctly. It begins with a preparation during which the nonsupporting leg slides to the side and is then placed behind the supporting leg in the classical fourth position, supported by adequate positioning of the arms. From this position, the dancer pliés to initiate a turn on the supporting leg (placed in front) in the direction of the nonsupporting leg. While turning, the dancer remains on the vertical rotational axis with the head following and overtaking the body during each turn to maximise the time facing front. The Pirouette ends in a defined body pose adopted by placing the non-supporting leg on the ground and opening the arms. As a reference for the results of the SDA-M, both movements, the Petit pas assemblé and the Pirouette en dehors, were broken down into their functional phases. According to a functional biomechanics approach, complex movements can be conceptualised as solutions to given movement problems

Figure 1. Petit pas assemblé; functional phases are given above the stick figure cartoon, basic action concepts (BACs) are listed with numbers below the stick figures.

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Figure 2. Pirouette en dehors; functional phases are given above the stick figure cartoon, basic action concepts (BACs) are listed with numbers below the stick figures.

(Bernstein, 1967; Rieling, Leirich & Hess, 1967; Göhner, 1979, 1992). Each functional phase of a complex movement serves the purpose of solving one of its subordinate problems and reaching one of its subgoals. Functional phases are characterised by their role in reaching the overall movement goal, which leads to a differentiation between main and assisting phases. The main functional phase of a movement leads to the completion of the main goal, or solution of the main movement problem. Assisting functional phases lead to the completion of subgoals, with primary assisting phases being more important for reaching the main goal than secondary assisting phases. This principle can be applied to dance movements as well as movements from different types of sports (Göhner, 1979, 1992; Schack, 2004; Schack & Mechsner, 2006). For the two movements regarded in this study, functional phases were determined with the help of movement descriptions from the literature (Tarassow, 1977) and classical dance experts, and were confirmed by results of a previous study (Bläsing, Tenenbaum, & Schack, 2009). The Pirouette en dehors can be separated into four functional phases. The actual turn, including its initialisation, takes place during the main functional phase. It is prepared for by the plié (i.e., bending the knees), the main component of the primary assisting phase with the function of building up spring tension for the turn. During the first part of the preparation, the secondary assisting phase, the body is aligned facing front, the arms open to the sides and the non-supporting leg slides sideward; attention is focused on


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the following turn. In the following primary assisting phase, the second part of the preparation, the non-supporting leg slides back to the fourth position in which it is placed behind the supporting leg, the corresponding arm is moved to the front and the knees are bent (plié). This starting posture, especially the relation of foot distance and weight distribution, is crucial for the dancer’s ability to control the turn (Sugano & Laws, 2002). From here, the turn is initiated by pushing the ground with the non-supporting leg and moving the foot up to the knee of the supporting leg (where it stays throughout the turn), pushing up onto point or demi-point (the ball of the foot) with the supporting leg, and closing both arms in front. During the final assisting phase, the turn is halted, the non-supporting leg is placed on the ground, the arms open and a terminal pose is adopted. The Pas assemblé, as a smaller and rather transient movement, can be separated into three functional phases. The actual jump is the content of the main functional phase. The preparing plié and the landing in final plié are content of the assisting functional phases during which spring tension is built up for the jump and the energy is caught again, respectively. From the plié, one foot slides to the side in such a way that leg and foot are stretched at the beginning of the jump. Both stretched legs are joined together in the air before landing; therefore the Pas assemblé can be understood as a jump from one foot onto both feet, even though the sliding action also contributes to the lift-off. If the Pas assemblé is performed within a series of jumps, as this is often the case, the initial and the final assisting phase melt into each other, so that only two functional phases can be distinguished, resulting in a cyclic movement structure (see Göhner, 1992). Illustrations of the movements and their functional phases are given in Figures 1 (Petit pas assemblé) and 2 (Pirouette en dehors). According to the cognitive architecture model (Schack, 2004; Schack & Ritter, 2009), BACs can be understood as functional units for the control of actions on the level of mental representation, linking goals on the level of mental control to anticipated perceptual effects of movements. Within the movement organization, each BAC is characterised by its typical set of sensory and functional features. As an example, the BAC “bend knees” belonging to the Pirouette en dehors relates to a demi plié in fourth position that takes place during the preparation, prior to the turn. It is functionally related, and therefore mentally linked, to functional and perceptual aspects like building up spring tension for the turn, aligning the shoulders above the hips, pulling the knees sideways while bending them and spreading the weight between both feet in a well-balanced way. Potential spatial features of this concept therefore are down (movement of the body centre of mass), up (antagonistic straightening and alignment of the torso), far, right and left (knees pulling to the sides). As anchor concepts in our experimental design, BACs of the Pirouette en dehors and the Pas assemblé were defined in the form of verbal labels, which is common practice for classical dance. The BACs were defined and

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phrased with the help of experienced teachers and dancers as well as standard reference books on classical dance training (Lörinc & Merenyi, 1995; Tarassow, 2005; Vaganova, 2002). The set of BACs for each movement was arranged in such a way that was valid for experts and amateurs and could also be understood by novices after explanation and video demonstration. Twelve spatial parameters were presented as features that had to be related to the BACs, namely front, back, left, right, front-left, front-right, back-left, back-right, up, down, close and far. These spatial parameters were defined in an egocentric frame of reference, from the first person’s perspective, as cues used by the dancers to improve movement stability and quality of performance, not in an allocentric frame of reference linked to the external space in the salle de ballet or the stage. BACs of the Pas assemblé and the Pirouette en dehors are displayed in Figures 1 and 2, respectively, together with the stick figure illustrations and functional phases of the movements.

3. PROCEDURE The experiment took place in a lab at the university or in a quiet office in the theatre. Initially, the movements were demonstrated via a video clip and explained verbally by the experimenter, and the BACs were explained separately to assure that the participants had understood their content. Data collection was conducted using a paper-and-pencil task. For each movement, participants were handed sheets of paper displaying a table with one row for each BAC and with two columns. In the right column, one BAC was printed in each cell, whereas in the left column, the 12 spatial parameters were displayed in the same way for each BAC (see Figure 3). The order of BACs was randomly varied and was different for each participant. Participants were instructed to mark with a pencil the spatial parameters that they personally associated to performing the part of the movement described by the BAC; this task had to be repeated for each cell. Participants thereby assigned those spatial features to each individual BAC that they judged as positively associated to it, without being informed about the position or role of the BAC in the overall movement structure. The experimenter explained that the spatial parameters were explicitly to be understood in an egocentric frame of reference, from the first person’s perspective, not in an allocentric frame of reference linked to the salle de ballet or the stage, where the front is marked by the mirror or the audience, respectively. This was important to mention because in classical dance it is common to work with external (allocentric) spatial cues to define directions for (partial) movements and to align the dancers’ bodies in space. In this case, we were rather interested in the associated (egocentric) spatial cues that are used by the dancers to improve the stability and quality of movement performance and that are therefore closely linked to movement structure. During data collection, participants were allowed to stand up and mark or


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Figure 3. Example of questionnaire for paper-pencil task. Participants were instructed to mark as many of the space concept labels as they whished for each BAC, but at least one and not all of them. BACs appeared in random order, varying for each participant.

try the movements in order to facilitate their decisions if they wished. After the participants had finished the task, they handed the sheet back to the experimenter. Subsequent to the data collection, the experimenter analysed the data using the Structure Dimensional Analysis-Motorics (SDA-M, Lander & Lange, 1996; Schack, 2004). This method has been used to analyse mental representations of movements in long-term memory of dancers (Bläsing, Tenenbaum, & Schack, 2009) and athletes (e.g., Schack, 2004; Schack & Mechsner, 2006). The SDA-M consists of four steps: First, a special splitting procedure involving a multiple sorting task delivers a distance scaling between the BACs of a suitably predetermined set. Second, a hierarchical cluster analysis is used to transform the set of BACs into a hierarchical structure. Third, a factor analysis reveals the dimensions in this structured set of BACs, and fourth, the cluster solutions are tested for invariance within- and betweengroups (for psychometric details, see Schack, 2010). In the present study, the method was applied to elicit the relational structure of BACs of the two dance movements in the participants’ long-term memory based on spatial features of performance. The experimental procedure started by collecting information on the representational distance between selected BACs (step 1) through the application

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of a special splitting technique in which participants judged each feature from the given set as associated or not associated to each of the BACs. In this study, this was achieved here via the paper-and-pencil task described above. The set of spatial features was thereby split into a group of associated items (marked by the participant) and a group of not associated items (not marked by the participant) for each anchor (BAC). In the tables handed out to the participants, each BAC was presented as anchor with the full set of spatial features, and participants had to assign the features to each of the anchors. From this procedure resulted a matrix of partial quantities (BACs features; i.e., a 16 12 matrix for the Pirouette, and a 9 12 matrix for the Pas assemblé). In this matrix, values took either a negative or positive sign depending on whether the feature was judged as belonging to or not belonging to the anchor (e.g., if 4 out of the 12 features were judged as belonging to a BAC, these items were each given the value C4, whereas the remaining eight features judged as not belonging to the BAC were each given the value 8). The resulting values were then z-transformed and subsequently transformed into Euclidian distances. The individual representation structure was determined by means of a hierarchical cluster analysis in Euclidian workspace (step 2). For the cluster analyses, alpha-levels of ˛ D 0:05 for the Pas assemblé and ˛ D 0:01 for the Pirouette were used, resulting in probabilities of error of dc r i t D 3:49 for the Pas assemblé and dc r i t D 4:59 for the Pirouette en dehors. To determine classification probabilities of features in relation to BACs, the initial z-matrix was transformed into a probability matrix; this p-matrix consists of p-values that indicate the classification probabilities of features to individual BACs belonging to clusters. In this study, only p-values above a critical value of pc r i t D 0:7 were considered as relevant. The factor analysis (step 3) that can be applied for direct scaling methods (BAC BAC) to reveal concepts dimensions was not relevant in this case and was therefore not used here, because spatial features were already predetermined as scaling criteria in the current study. Finally (step 4), a pair-wise between-group comparison of the cluster solutions was performed using an invariance measure to determine their structural invariance (Lander, 1991; Schack, 2010). The structural invariance measure was determined based on three defined values, the number of constructed clusters of the pair-wise cluster solutions, the number of elements (concepts) within the constructed clusters, and the average quantities of the constructed clusters. The value was calculated as the square root of the product of the weighted arithmetic means of the relative average quantities of the constructed clusters and the proportional number of clusters in the compared cluster solutions. In the present analysis, two structures were declared invariant if they possessed a higher value than the defined differential threshold c r i t D 0:68.


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4. RESULTS 4.1. Petit Pas Assemblé The cluster solutions of the experts’ group included three clusters, whereas the amateurs’ and the novices’ cluster solutions included two clusters each. Both the experts and the amateurs defined a cluster for the main functional phase that included the movement concepts 3 (right foot slides to side), 4 (lift right leg), 5 (jump from left leg) and 6 (stretch left leg in air). Both groups associated this cluster mainly with the spatial concepts up and right, and partially with far. In both groups, BAC 3 was also associated with down. The experts combined the remaining BACs in two clusters, one consisting of BACs 1 (stand, left foot in front) and 7 (join legs) associated with up, front and close, and the other one consisting of BACs 2 (bend knees) and 8 (land on both feet) mainly associated with down. Amateurs combined all five remaining BACs in one cluster associated with front, and partially with close and down. Novices defined two clusters including BACs 2, 8 and 9 (bend knees, stretch) associated with down and close, the other one including BACs 3 and 4 associated with right and far. Results of the invariance analysis showed that cluster solutions of all experimental groups differed significantly from each other (experts vs. amateurs: D 0:51, amateurs vs. novices: D 0:61, experts vs. novices: D 0:42). Cluster solutions for the Pas assemblé are presented as dendrograms in Figure 4 on the left, and clusters associated with direction concepts are presented in Table 1.

4.2. Pirouette en Dehors The cluster solution of the experts’ group included two clusters, the larger one consisting of BACs 9 (close arms), 10 (push left leg into ground), 11 (right foot up to left knee) and 12 (turn head), the smaller one consisting of BACs 2 (open arms for preparation) and 3 (right foot slides to side). The larger cluster was associated with the spatial features up and close, whereas the smaller one was associated with up, front, right and far. The amateurs’ cluster solution included three clusters, a large one consisting of BACs 1 (stand, right foot in front), 4 (move right arm to front), 7 (locate eye focus), 9 and 13 (relocate eye focus) and two pairs, BACs 6 (bend knees) and 16 (bend knees, stretch) and BACs 10 and 11. The large cluster was strongly associated with the spatial concept front, the pairs were mainly associated with down and front and with up and front, respectively. The results of the novices’ group did not contain any cluster. Results of the invariance analysis revealed that the cluster solutions of amateurs and experts differed significantly from each other . D 0:34/. Cluster solutions for the Pirouette en dehors are presented as dendrograms

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Figure 4. Results of the cluster analysis via SDA-M for the Petit pas assemblé (left column) and the Pirouette en dehors (right column) displayed as dendrograms. Top panel: experts (Pas assemblé: N D 15; Pirouette: N D 17); middle panel: amateurs (N D 18); bottom panel: novices (N D 19). Numbers on the bottom line mark BACs, boxes indicate clusters; numbers on the right (relating to links between items, i.e., horizontal bars in the dendrogram) indicate Euclidean distances between BACs (the lower the link between items, the shorter is the distance between the corresponding BACs in long-term memory). The horizontal dashed line indicates the dc r i t value for the given ˛ probability; only structural links below this value are considered relevant (Petit pas assemblé: ˛ D 0:05, dc r i t D 3:49; Pirouette en dehors: ˛ D 0:01, dc r i t D 4:59). BACs of the Petit pas assemblé (left): (1) stand, left foot in front; (2) bend knees; (3) right foot slides to side; (4) lift right leg; (5) jump from left leg; (6) stretch left leg in air; (7) join legs; (8) land on both feet; (9) bend knees, stretch; BACs of the Pirouette en dehors (right): (1) stand, right foot in front; (2) open arms for preparation; (3) right foot slides to side; (4) move right arm to front; (5) move right foot back; (6) bend knees; (7) locate eye focus; (8) stabilize body axis; (9) close arms; (10) push left leg into ground; (11) right foot up to left knee; (12) turn head; (13) relocate eye focus; (14) close right foot behind left; (15) open arms after turn; (16) bend knees, stretch.


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Table 1. Petit pas assemblé: cluster solutions (SDA-M) and associated space direction concepts Group Experts

Clusters I II III*

Amateurs

I

II*

Novices

I

II

Basic action concepts 1. 7. 2. 8. 3. 4. 5. 6. 1. 2. 7. 8. 9. 3. 4. 5. 6. 2. 8. 9. 3. 4.

stand, left foot in front join legs bend knees land on both feet right foot slides to side lift right leg jump from left leg stretch left leg in air stand, left foot in front bend knees join legs land on both feet bend knees, stretch right foot slides to side lift right leg jump from left leg stretch left leg in air bend knees land on both feet bend knees, stretch right foot slides to side lift right leg

Associated space direction concepts up (.88), front (.84), close (.72) up (.96), front (.73), close (.82) down (.92), up (.77) down (.95), close (.77) up (.77), right (.91), far (.70), down (.76) up (.92), right (.95), far (.73) up (.97), right (.81) up (.98), right (.74) front (.96), close (.88) front (.87), down (.96) front (.85), close (.80), up (.73) front (.89), close (.85), down (.95) front (.92), close (.81), down (.92), up (.70) up (.73), right (.95) up (.92), right (.95), far (.81) up (.97), right (.84), far (.77), front (.70) up (.97), right (.73), far (.76) down (.99), close (.73) down (.97), close (.81), front (.79) down (.99), close (.71) right (.94), far (.80) right (.92), far (.86), up (.87)

Numbers in the last column mark probability values (only p-values above a critical value of pcrit D 0:7 are considered); *cluster corresponding to the main functional phase.

in Figure 4 on the right, and clusters associated with direction concepts are presented in Table 2.

5. DISCUSSION Before we turn to the general discussion, results for each of the two movements will be discussed separately. For the Petit pas assemblé, experts and amateurs defined one cluster that corresponded directly to the main functional phase. Both groups associated this phase mainly to the spatial concepts up and right. Amateurs combined all other BACs into one cluster, associated with front and close. This cluster solution might reflect the following situation: if the Pas assemblé is performed in a series of small steps and jumps, the two assisting functional phases melt into each other, comparable to those of a cyclic movement. According to Göhner (1992), initial and final assisting phases of cyclic movements, such as turns in alpine skiing, melt into each other if the movement is performed in the usual fluent way (i.e., not separated artificially, e.g., for demonstration purposes).

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Table 2. Pirouette en dehors: cluster solutions (SDA-M) and associated space direction concepts Group Experts

Clusters I II*

Amateurs

I

II III

Basic action concepts 2. 3. 9. 10. 11. 12. 1. 4. 7. 9. 13. 6. 16. 10. 11.

open arms for preparation right foot slides to side close arms push left leg into ground right foot up to left knee turn head stand, right foot in front move right arm to front locate eye focus close arms relocate eye focus bend knees bend knees, stretch push left leg into ground right foot up to left knee

Associated space direction concepts up (.88), front (.84), right (.76), far (.75), left (.71) up (.80), front (.79), right (.83), far (.81) up (.89), close (.87), front (.81) up (.96), close (.82) up (.95), close (.76) up (.87), close (.84), front (.94) front (.96), close (.87) front (.97) front (.98), far (.70) front (.95), close (.94) front (.98) down (.95), front (.79) down (.92), front (.79), up (.76), close (.76) up (.96), front (.87) up (.93), front (.78), right (.76)

Numbers in the last column mark probability values (only p-values above a critical value of pcrit D 0:7 are considered); * cluster corresponding to the main functional phase.

This also applies to the Pas assemblé in the case that it is performed as part of a sequence of jumps. It seems therefore plausible to assume that mentally structuring the movement in this way facilitates the execution of the Pas assemblé in its usual form, as part of a sequence. The experts also combined BACs of the two assisting phases, but they appeared in two pairs of clusters characterised by different associated spatial features; one was most strongly linked to the upward direction, whereas the other was rather linked to the downward direction. This result might reflect a more differentiated spatial representation, but violates the correct time structure of the movement. Novices formed two clusters; one of the clusters contained two BACs belonging to the main functional phase, but associated them with the spatial features right and far instead of up, which would have been functionally adequate for a jump. The other cluster combined BACs from the assisting phases in a similar way as in the amateurs and experts and associated them with down and close. In general, the upward direction was hardly present in the novices’ results, whereas it clearly dominated the representation of the main functional phase in the amateurs and experts, as expected for a jump. Results of the Pirouette en dehors differ profoundly from those of the Pas assemblé. Crucially, novices did not produce any cluster at all, and cluster solutions of experts and amateurs differed more obviously than for the Pas assemblé. Comparing the cluster solutions of the experts and the amateurs, it stands out that one of the clusters defined by the experts clearly reflected the main functional phase of the Pirouette en dehors, and the second cluster included two BACs that belonged to the secondary assisting phase of the preparation. In contrast, none of the amateurs’ clusters clearly reflected any of the functional phases, even though the third cluster contained two BACs


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belonging to the main functional phase. Both experts and amateurs associated the cluster corresponding to the main functional phase with the spatial concept up. The amateurs also associated it with front, whereas the experts associated it with close, which is likely to reflect an active tightening and pulling in order to stabilize the turning axis and increase turning speed. The latter aspect is specifically important during the turning phase in which body rotation is mainly based on inertia and no active motion of body parts occurs except for isolated turns of the head (see Sugano & Laws, 2002). Dynamic stability during whole body rotations requires stabilization of the turning axis, especially of the supporting leg, as well as stable alignment of shoulders and hips. In a study by Golomer, Touissant, Bouillette, and Keller (2009), dancers maintained shoulders and hips en bloc for turns in both directions, whereas in untrained controls, shoulder hip angles deviated depending on the turning direction, supporting leg and phase of the turn. Empirical findings like this suggest that control of dynamic equilibrium during whole-body rotations is based on learned strategies that are highly sensitive to training effects, and mental association of adequate spatial parameters such as up and close most likely belongs to these strategies. Taking the presented results of both movements into account, we would like to emphasize three major aspects. First, the study revealed differences between professional dancers, amateurs and novices regarding their mental representations of the two movements based on associated spatial parameters. Secondly, the way in which cluster solutions of professional dancers, amateurs and novices differed was in a remarkable way movement-specific. For the Pas assemblé, similar representations referring clearly to the functional phases emerged in amateurs and professional dancers, with the main functional phase being characterised by adequate spatial parameters, and a less functional representation emerged in the novices. For the Pirouette, the experts’ structure was the only one that contained functional clusters based on adequate spatial parameters, whereas the amateurs‘ cluster solution was not functional, and novices did not produce any cluster. These results suggest that well defined spatial parameters in long-term memory might be specific for highly skilled experts, especially for complex movements such as the Pirouette. Therefore, the approach taken here could represent a rather sensitive measure of movement expertise. A third aspect arises when we look at a former study by Bläsing, Tenenbaum, and Schack (2009) and compare the results to those of the current study. This comparison shows that cluster solutions obtained via direct and indirect scaling differ in a way that is specific not only for the level of expertise and movement type, but also for the criteria on which the scaling is based. In the previous study, the same two dance movements, the Petit pas assemblé and the Pirouette en dehors, were analysed using the SDA-M method based on direct scaling (BAC BAC), without the definition of concept features as scaling criteria (Bläsing, Tenenbaum, & Schack, 2009).

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In the results for the Pirouette en dehors, professional dancers’ and advanced amateurs’ representational structures reflected the complete four functional phases, whereas the beginners’ cluster solution showed only a small consistency with the functional phases, and the novices’ results did not show any structure at all. For the Pas assemblé, only the experts’ group included the main functional phase into one cluster, whereas amateurs and novices separated the main functional phase in a way that reflects a nonfunctional integration of this part of the movement. In contrast, in the current study functional clusters occurred almost exclusively for the main functional phases of the movements, and for the more complex movement, the Pirouette, this was only the case for the experts. This finding might be explained by the assumption that the spatial parameters used here as scaling criteria did not suffice for characterizing the concept features completely, and that other (e.g., temporal) features would be needed to determine the complete cluster solutions that were obtained in the previous study via direct scaling. In another previous study, mental representations of the front loop in wind surfing were determined by direct scaling (BAC BAC) and by indirect scaling (BAC feature) via temporal, spatial and force features. Cluster solutions of both approaches showed a high similarity, suggesting that the set of features in this case was sufficient to span the feature space of the movement concepts (Schack, 2010). This was not the case in the current study, however, it can be concluded from the current results that, at least for dance experts, spatial parameters in an egocentric reference frame are a major factor determining movement organisation on the level of the main movement goal. Dancers’ extensive and specific movement experience evidently shapes their cognitive representation of movement-related spatial information. The presented findings shall therefore be regarded in the context of research investigating the role of motor expertise and kinaesthetic experience for knowledge representation. According to the embodiment perspective, cognitive processes are strongly influenced by sensory and motor processes. This implies that similarities in frequently performed motor actions generate similar mental representations of movement and space. Dance experts represent a valuable group of individuals to study this principle; trained dancers differ from other individuals in terms of their physical configuration, motor experience and cognitive control of movement tasks. Recently, several authors have turned to expert and novice dancers to investigate how motor expertise shapes brain activity in action observation, and how the brain links action with perception in learning coordinated fullbody movements. Studies using fMRI revealed that expert dancers show increased activity in specific brain areas including inferior parietal and premotor cortices while watching movements from their own motor repertoire, compared with similar movements from a different discipline they had not performed before (Calvo-Merino, Glaser, Grèzes, Passingham, & Haggard, 2005; Cross, Hamilton, & Grafton, 2006). In an EEG study, dancers showed


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stronger de-synchronization of the motor cortex (indicating motor simulation) than non-dancers while watching dance movements (Orgs, Dombrowski, Heil, & Jansen-Osmann, 2008). Subsequent studies were carried out to further dissociate how brain responses during action observation are modified by visual or motor experience. In a study by Calvo-Merino and colleagues, male and female dancers watched common gender-neutral movements as well as gender-specific movements that are exclusively performed by either males or females (Calvo-Merino, Grèzes, Glaser, Passingham, & Haggard, 2006). The authors found that premotor and parietal regions responded specifically to movements the observers had practiced compared to movements that were only visually familiar. In a study with novice dancers learning movement sequences by either physical practice or passive observation, Cross and colleagues demonstrated similarities between physical and observational learning within parietal and premotor regions, supporting the notion that physical and observational learning shape brain and behavior in a similar way (Cross, Kraemer, Hamilton, Kelley, & Grafton, 2009). Evidence from these studies suggests that motor experience influences the brain processes involved in action observation, implying that experts differ from novices in their perception and subjective experience of movement tasks. Empirical evidence also exists for the notion that the nature and vividness of embodied representations is influenced by dance training. A special tool used strategically by dancers for learning and optimizing movements is the mental imagery of movement. Dancers use mental imagery to exercise the memorization of long complex phrases and to improve movement quality in terms of spatiotemporal adaptation and artistic expression. Dance training has been found to increase the amount and efficiency of kinaesthetic imagery and to enhance the imagery of kinaesthetic sensations, making images more complex and vivid (Golomer, Bouillette, Mertz, & Keller, 2008; Nordin & Cumming, 2007). Empirical findings have corroborated that motor imagery is based on simulation processes that recruit motor representations, and that imagery, observation and execution of movement have been found to share a major part of their neural correlates (Jeannerod, 1995, 2001; Schütz-Bosbach & Prinz, 2007a, 2007b). Motor imagery in the absence of sensory input was found to specifically necessitate internal motor attention processes (Munzert, Zentgraf, Stark, & Vaitl, 2008). Increased beta activity in a broad range of cortical areas also indicated states of high concentration (Blaser & Hökelmann, 2004, 2009). The flexible and adaptive deployment of spatial and temporal movement characteristics in imagery is a cognitive tool used by dancers who train on a high level. Specifically, associating spatial parameters in an egocentric reference frame to movement representations in order to improve the stability and quality of movement performance is common practice in various dance disciplines. Based on the findings that execution, performance and imagery of

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movements share neural correlates, and that dance experts use motor and kinaesthetic imagery in their training, including imagery of body-centred spatial parameters, results of the current study suggest that dance experts develop specific cognitive representations of dance movements via a combination of extensive motor experience and strategically applied techniques. These mental representations involve spatial features of movement concepts in a way that is empirically accessible and that is likely to play a major role in supporting dancers’ high-level performance. Dance experts evidently differ from novices in the way they use embodied processes, specifically spatial information associated to movement tasks.

6. CONCLUSION Dance experts, compared with novices and amateurs, have special embodied representations of dance movements that include information about spatial parameters in an egocentric frame of reference. The analysis of mental representations of classical dance movements via their associated spatial parameters revealed representation structures that differentiated the three expertisebased groups in a movement-specific way. Main phases of both movement tasks were represented in the cluster solutions obtained via adequate spatial features; for the more complex movement, this was only the case for the group of professional dancers. The results differed from those obtained in a previous study (Bläsing, Tenenbaum, & Schack, 2009) in which no spatial concept features had been predefined as scaling criteria; in this case experts’ and advanced amateurs’ results reflected the complete movement structures represented as functional phases. It can be concluded that expert training in dance results in mental representations of embodied tasks that can be empirically differentiated from amateurs’ and novices’ representations via the spatial features of their movement concepts. Findings support the general perspective that embodied processes in spatial cognition can be strategically applied to reach goals, adding the notion that this might require specialist training, extensive motor experience and a high performance level as it is found in professional dancers. Dance experts evidently represent a valuable group to investigate in how far motor experience plays a crucial role in shaping differences in embodiment.

ACKNOWLEDGMENTS The authors would like to thank the dancers and the management of the aalto ballett theater essen, Ballett Dortmund, Tanztheater Bielefeld, and all other participants. Specifically, we thank Martin Puttke for fruitful discussions and professional advice on classical dance technique.


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