A dance to the music of time: aesthetically-relevant changes in body posture in performing art.

Abstract

In performing arts, body postures are both means for expressing an artist's intentions, and also artistic objects, appealing to the audience. The postures of classical ballet obey the body's biomechanical limits, but also follow strict rules established by tradition. This combination offers a perfect milieu for assessing scientifically how the execution of this particular artistic activity has changed over time, and evaluating what factors may induce such changes. We quantified angles between body segments in archive material showing dancers from a leading company over a 60-year period. The data showed that body positions supposedly fixed by codified choreography were in fact implemented by very different elevation angles, according to the year of ballet production. Progressive changes lead to increasingly vertical positions of the dancer's body over the period studied. Experimental data showed that these change reflected aesthetic choices of naïve modern observers. Even when reduced to stick figures and unrecognisable shapes, the more vertical postures drawn from later productions were systematically preferred to less vertical postures from earlier productions. This gradual change within a conservative art form provides scientific evidence that aesthetic change may arise from continuous interaction between artistic tradition, individual artists' creativity, and a wider environmental context. This context may include social aesthetic pressure from audiences.

Full text

Page 1

A Dance to the Music of Time: Aesthetically-Relevant
Changes in Body Posture in Performing Art
Elena Daprati1,2, Marco Iosa3, Patrick Haggard4*
1Dipartimento di Neuroscienze and Centro di Biomedicina Spaziale, Universita ` degli Studi di Roma Tor Vergata, Roma, Italy, 2Dipartimento di Fisiologia Neuromotoria,
IRCCS Fondazione Santa Lucia, Roma, Italy, 3Dipartimento di Scienze del Movimento Umano e dello Sport, Istituto Universitario di Scienze Motorie, Rome, Italy, 4Institute
of Cognitive Neuroscience, University College London, London, United Kingdom
Abstract
In performing arts, body postures are both means for expressing an artist’s intentions, and also artistic objects, appealing to
the audience. The postures of classical ballet obey the body’s biomechanical limits, but also follow strict rules established by
tradition. This combination offers a perfect milieu for assessing scientifically how the execution of this particular artistic
activity has changed over time, and evaluating what factors may induce such changes. We quantified angles between body
segments in archive material showing dancers from a leading company over a 60-year period. The data showed that body
positions supposedly fixed by codified choreography were in fact implemented by very different elevation angles,
according to the year of ballet production. Progressive changes lead to increasingly vertical positions of the dancer’s body
over the period studied. Experimental data showed that these change reflected aesthetic choices of naı ¨ve modern
observers. Even when reduced to stick figures and unrecognisable shapes, the more vertical postures drawn from later
productions were systematically preferred to less vertical postures from earlier productions. This gradual change within a
conservative art form provides scientific evidence that aesthetic change may arise from continuous interaction between
artistic tradition, individual artists’ creativity, and a wider environmental context. This context may include social aesthetic
pressure from audiences.
Citation: Daprati E, Iosa M, Haggard P (2009) A Dance to the Music of Time: Aesthetically-Relevant Changes in Body Posture in Performing Art. PLoS ONE 4(3):
e5023. doi:10.1371/journal.pone.0005023
Editor: Nicola Clayton, University of Cambridge, United Kingdom
Received January 9, 2009; Accepted January 22, 2009; Published March 26, 2009
Copyright: ? 2009 Daprati et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This research was funded by a Leverhulme Trust project grant, and a BBSRC ISIS grant awarded to PH. The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: p.haggard@ucl.ac.uk
Introduction
Artistic culture appears to be a uniquely human attribute.
Although art exists in many forms, three characteristic features are
commonly present. These include a creative artist, an ‘‘art object’’,
and an observer or audience. The combination of the first two
features may result in a particular class of psychological experience
in the observer, which has been called ‘aesthetic experience’ [1].
Here we explore the relation between individual aesthetic
experience and changes in art objects over extended period of
time. The nature of aesthetic experience, and its neural basis, have
both been hotly debated. One tradition has sought more or less
universal principles of aesthetic experience. For example, simple
geometrical relations were proposed to explain preferences for
some abstract shapes above others [2–4]. However, these effects
are often small and far from universal. Even the best known, such
as the ‘golden section’ [5–6] have proved difficult to replicate [7].
An alternative viewpoint questions the validity of aesthetic
universals, and instead points to the clear and important role of
culture in aesthetic evaluation. For example, aesthetic preferences
might result from an extension of the laboratory effect of mere
exposure [8], whereby we come to like what is familiar [9].
However, since this view reduces aesthetic experience to
repetition, it predicts that artistic culture should be rather static.
It cannot account for changes in artistic production, nor for the
role of individuals’ aesthetic experience in such change. In fact,
artistic culture often involves a balance between the traditions
(‘‘schools’’) of a particular art form, and innovation or change. The
role of artistic tradition may explain why some art forms are
gradually perfected over time, achieving potent and lasting effects
on individuals and even whole societies. The role of innovation
may explain why mimicry alone is not generally considered
artistic.
Changes in artistic expression arise from the creative processes
of the individual artist, but also reflect a wider environmental
context, such as enabling technologies, audience feedback, and
market forces. In performing arts, factors related to the artists’
fitness, motor capabilities and training would also be an issue. The
dynamics of this balance between tradition and innovation have
often been described by art historians [10]. Interestingly, however,
they have received much less attention from scientists, despite a
clear similarity to general principles of exploitation vs. exploration
that underlie evolution of individual and group behaviors [11].
One reason for the lack of scientific attention may be that artistic
change is often unconstrained, and difficult to quantify, reflecting
the fact that human creativity appears infinite [12]. However, in
some cases, changes are more subtle and can be objectively
quantified, for example because change occurs within a strong
artistic tradition, or because the raw material is intrinsically
limited. Such cases provide a benchmark for a scientific
understanding of how and why artistic cultures may change and
develop.
PLoS ONE | www.plosone.org1March 2009 | Volume 4 | Issue 3 | e5023

Page 2

Classicalballetoffers one suchcase,asitinvolvesquantifiable raw
material in the form of human body postures, a strong and clearly
defined artistic tradition, and rich objective documentation in the
form of archives. These conditionsallowedus to focus on changes in
small number of quantifiable variables, repeated across different
individual artists, and spanning a suitable period of time. Ballet is a
dance form, which uses a single, codified, set of positions of the
human body to express emotions and other mental states. Because
the positions of the human body are biomechanically constrained,
the artistic raw material is limited. Classical ballet is traditional and
conservative: dancers today use the same positions that were
codifiedin1760[13],andoftenfollowchoreographiesestablishedin
the 19th century. The body positions appropriate at each moment
in the ballet are transmitted between generations within ballet
companies by observational learning and instruction [14], by books
of notation [15] and more recently by video records. More
importantly, body positionscanbe easilymeasuredfrom thearchive
material, providing a suitable database for scientific investigation.
This combination allowed us to compare successive artistic
interpretations of a fixed piece of choreography. Specifically, we
tested the hypothesis that performing arts show a slow, progressive
change that parallels the changing aesthetic preferences of
audiences. For this purpose, we explored whether successive
dancers have modified the expression of standard body postures,
despite the codified rules of classical dance, and the constraints
imposed by the laws of biomechanics. Because dance aims to
produce aesthetically relevant visual patterns using the dancer’s
body as raw material, such variation could either reflect changes in
dancers’ flexibility and muscular strength, or could reflect
changing aesthetic references. We tested this second possibility
in an additional study by investigating the aesthetic impact of the
visual patterns produced by the dancers’ bodies in our dataset.
Results
Study 1: Tracing progressive changes in body postures
Ballet positions are codified, and limited by biomechanics’ rules.
Theoretically, they should present in identical form across time,
except for slight random variations due to variability between
individual dancers. Study 1 aimed to investigate whether variation
across time in specific ballet positions is indeed random, or whether
thereisasystematictrendacrosstime.Forthispurpose,weselected a
single piece of choreography from The Sleeping Beauty. This work
has been performed in essentially identical form across decades [16].
Within this single piece, we chose canonical, codified body positions
that occurred with several consistent repetitions, so that we could
average repeated measurements (see Figure 1 and Methods).
We collected photographs and video material from the archive
of the Royal Opera House, Covent Garden, covering Royal Ballet
productions in the period 1946–2004 (see Methods). We measured
joint angles from the archive material, concentrating on the angle
of elevation of the leg in six standard body positions (see Methods).
Joint angle measures were chosen because they are independent of
the dimensions of the image, of the camera-dancer distance, and of
the body size and body proportions of the individual dancer. We
related the angle of elevation to the year of each production of The
Sleeping Beauty and performed separate regression analyses for
each selected body position.
Figure 2 shows representativeexamples ofthe correlation analyses
relating the angle of leg elevation to the year of each production of
The Sleeping Beauty for three of the selected body positions (see
Table 1 for statistics). Clearly, despite the codified positions
established by the choreography, there are systematic differences
in elevation angles according to the year of ballet production.
In the first example (panel A), the angle of the working leg
increases progressively with time (see Table 2 for mean values).
Since the ballerina is unsupported, this historical variation
corresponds to a considerable increase in the skill required to
maintain balance, while still producing a defined and expressive
geometry of the body. Interestingly, the variability between
successive reproductions of a given body position by the same
dancer in one production is low, reflecting their high levels of motor
skill. In contrast, the variability in average leg elevation across years
is relatively high. This suggests that the historical trend cannot be
due merely to a sampling bias in the particular images chosen for
measuring leg elevation. Table 3 shows an example comparing
variability across dancers and variability within a single dancer, for
the case of the body position shown in Figure 2A).
In addition, our analyses show that the increasing leg elevation
is a specific change in the movement of the working leg. A
biomechanical analysis of this change suggests that the leg is lifted
in order to achieve a desired vertical line of the whole body. If the
aim were merely to lift the leg as high as possible, greater leg
elevation can always be achieved by inclining the trunk towards
the horizontal. However, we found that the trunk angle was
maintained despite increased leg elevation (see Table 1). Maximal
abduction of the working leg is likely to involve greater external
rotation of the hip (‘‘turnout’’). Several studies emphasize the
correlation between leg abduction and hip external rotation [17–
19]. Moreover, turnout is a basic, yet critical aspect of ballet
training: elite dancers tend to show greater hip external rotation
compared to controls. We therefore speculate that the effect of
increasing leg elevation arose from perfecting this basic building
block of ballet body position. By progressively increasing the
functional range of movement of the working leg, the dancer is
offered the opportunity to produce the pose that best matches the
current aesthetic choice: here, making the overall bodyline more
vertical (at least across this historical period).
The hypothesis that the progressive change towards more
vertical positions is not mere virtuosity or display a dancer’s
maximal performance ability but rather reflects changing aesthetic
choices is supported by the finding that this trend is quite general.
It emerges in postures where leg elevation does not approach the
maximum values and in dancers of different experience. Thus,
figure 2B shows a trend towards increasing elevation in a position
where the ballerina is supported by the male dancer. The presence
of additional support makes this posture less biomechanically
demanding than the posture of Figure 2A. The leg could therefore
be lifted higher than it actually is even in older productions.
However, the dancer’s body tends towards a more vertical line
only in the later productions within our time period, even for these
positions in which a vertical line was always possible. Similarly, the
trend towards verticality is shared by the dancers interpreting the
‘‘Fairy of purity’’, a short variation traditionally executed by a
younger or less experienced dancer (see Table 1).
Taken together, these findings suggest that variations across
time in the elevation of the working leg have occurred for iconic
moments in classical ballet. These variations may certainly reflect
progressive variations in skill level and dancers’ physical fitness.
However, as the artists differentially make use of this advantage,
we suggest these changes may also reflect aesthetic choices. This
possibility was directly addressed in Study 2.
Study 2: Aesthetic relevance of the historical change in
body postures
In Study 2 we directly assessed the hypothesis that the reported
progressive variation in body positions reflects a change in aesthetic
evaluation. We used the established method of aesthetic preference
Changes in Body Posture
PLoS ONE | www.plosone.org2 March 2009 | Volume 4 | Issue 3 | e5023

Page 3

judgment [20]. We transformed our images into a standardized
form, by making separate sets of stick figures based on the principal
body segments, and quadrilateral shapes, by connecting the
endpoints of each limb in each image. The latter were not obviously
recognizableashumanbodies.Twelvenaı ¨vevolunteersparticipated
onthebasisofwritteninformedconsent.Eachparticipantviewed all
possible pairings of stick figures, and all possible pairings of
quadrilateral shapes for each body position. They judged which
image of each pair they preferred. We averaged preferences across
participants,tocalculatea preferencecoefficientforeachstickfigure
or quadrilateral shape, and used linear regression to relate our
participants’ preference of each figure or shape to the year of the
production from which each original image was selected. The
experiment did not seek to identify any universal aesthetic rules, but
only to investigate whether historical changes in artistic production
were relevant to the aesthetic experience of our participants. The
study procedures were approved by UCL’s Department of
Psychology ethics committee.
Both the regression analysis for stick figures and shapes were
significant (Figure 3). Namely, there was a significant tendency for
Figure 1. Anatomical references for angle analysis and stimuli for the aesthetic preference experiment. A. Body-part labelling and joint
angle calculation. Three independent judges positioned a digital marker on the major joints and body-parts. Marker locations were used to compute
limb and axial segments and to define angles. They were also employed in producing stick figures and polygons. B. Stick figures and geometric
shapes used in aesthetic preference task (see text for details). Stick figures were obtained by joining the markers shown in A; polygons were defined
by the limb endpoints of the stick figure. The labels on the stick figure and polygon were not present during testing.
doi:10.1371/journal.pone.0005023.g001
Changes in Body Posture
PLoS ONE | www.plosone.org3 March 2009 | Volume 4 | Issue 3 | e5023

Page 4

figures and shapes drawn from later productions to be preferred to
those from earlier productions. Besides, the mean of regression
slopes for each individual combination of image type (stick figure/
shape) and body position had an average significantly greater than
zero (p=0.029), suggesting a general relation between production
year and aesthetic evaluation.
Based on these findings, we suggest that the historical variation of
body positions shown in Study 1 may reflect changing aesthetic
evaluations of body posture. The consensus of our participants
showed that greater elevation angles of recent Sleeping Beauty
productions are, in general, preferred to lower elevation angles of
earlier productions. We found similar preferences even when bodies
were transformed into abstract geometric shapes. Preferences for
verticality in geometric shapes have been reported previously [4].
Here, the dancers’ postures were adjusted to generate a progres-
sively more vertical shape over time. The modifications of body
posture in classical dance had implications on the average aesthetic
response of our contemporary non-expert participants.
Figure 2. Three representative examples of the body positions analysed. Panel A: A highly skilled, unsupported position. The leg elevation
that the dancer can achieve depends on her flexibility and her ability to simultaneously maintain balance; Panel B: A highly skilled, supported
position. Balance is made easier by the male dancer’s support, and leg elevation depends largely on flexibility; Panel C: A less skilled, unsupported
position. The leg elevation required by the choreography is less demanding compared to the posture in panel A and balance is less critical, as the
position should be maintained only for a brief time. In each panel: right side - correlation between year (x-axis) and degree of leg elevation (y-axis),
r=Pearson correlation coefficient; left side - upper row, archive material showing the positions where the angle was recorded; lower row: stick figures
showing the mean angle for the corresponding year. The angles measured from these illustrative images appear as red dots along the corresponding
regression line.
doi:10.1371/journal.pone.0005023.g002
Changes in Body Posture
PLoS ONE | www.plosone.org4 March 2009 | Volume 4 | Issue 3 | e5023

Page 5

Our statistical design treated participants as a fixed effect, and
body postures as a random effect: it therefore generalizes across
ballet postures but does not make any attempt to generalize across
people. Indeed, psychological studies of aesthetics, which aim at
generality across individuals, typically show much smaller effects
despite much larger subject numbers [3]. Therefore, we can only
speculate on whether our results would generalize to other groups
of subjects, or to other historical periods. For example, our result
suggests that if we had tested people at the start of our time-period,
in 1946, they should have preferred less vertical postures. But this
hypothesis seems difficult to test: aesthetic preferences vary within
individuals across time as a function of their experiences [8].
Therefore, individuals who preferred less vertical postures in 1946
might nevertheless prefer more vertical ones if tested now, due to
the intervening exposure to the increasing verticality we have
described. A more fruitful focus for future research might involve
comparing aesthetic preference judgments from different cultures,
and from individuals exposed to different dance forms [21], since
aesthetic preferences vary both across cultural groups, and across
individuals within groups [22].
Discussion
We have found a progressive and generalized change in the body
positions used to realize selected choreographic moments in
successive productions of a classical dance work. Specifically, across
several positions, several individual dancers, and several decades,
the working leg is lifted progressively higher. Since classical ballet
uses codified positions, and since the productions studied here all
used a fixed choreography, elaborated and transmitted by the
practice of a permanent ballet Company, this historical variation
within a single body position category may seem surprising. The
linear trend shows that variations in body position are systematic,
not random. Interestingly, although we specifically monitored leg
elevation angles, the trend clearly involves the global visual shape
produced by the posture. Indeed, dancers have not simply aimed at
progressively increased leg elevation per se. That could be achieved
by a corresponding change in trunk inclination, but we found no
evidence for changes in trunk position. Rather, the dancers
appeared to perfect the biomechanics of the movement, perhaps
by increasing hip turnout, and consequently the range of movement
of the working leg. Thisachieved the characteristic vertical bodyline
of recent productions, without modifying trunk position. From this
patternofevidence,weconcludethat the variationinleg elevationis
an example of progressive, systematic change within an artistic
tradition.
Fitness and/or aesthetics as causes of systematic change
Many factors influence artistic production. We here consider
two possible explanations for the historical changes in our dataset:
changing dancer fitness, and changing aesthetic preferences. On
the first view, change in body position is driven by increases in
dancers’ fitness and skill. Improvements in dancer selection,
training and physical condition have allowed successive genera-
tions of dancers to achieve and even exceed the codified body
positions laid down early in ballet tradition [13]. Perhaps the
dancers earlier in our period would have produced leg elevations
equal to those seen more recently, had they been physically able to
do so. That view suggests that dancers have throughout strived for
a ‘‘perfect’’ body position corresponding to a universal aesthetic
goal. Recent dancers have come closer to achieving this goal due
to their greater fitness and skill. This view has difficulty explaining
why dance forms differ widely across cultures. An alternative view
suggests that aesthetic goals are not fixed, but vary, despite the
Table 1. Correlation analyses for leg elevation and trunk inclination angles vs. year.
I. ANGLE1OF LEG ELEVATIONrpN
Adagio1 - Arabesque penche ´e (HS)2,3
0.831
,0.000214
2 - De ´veloppe ´ a ` la seconde (HS)2,4
0.788
,0.000515
3 - Arabesque roses (HS)2
0.871
,0.017
4 - Arabesque sur la pointe (LS)5,6
0.682
,0.01 12
5 - Pique ´ arabesque sur la pointe (LS)5
0.649
,0.059
Fairy of purity 6a - De ´veloppe ´ a ` la seconde - right leg (HS)2
0.795
,0.028
6b - De ´veloppe ´ a ` la seconde - left leg (HS)2
0.797
,0.028
II. ANGLE1OF TRUNK INCLINATIONrpN
Adagio 1 - Arabesque penche ´e (HS)2,3
20.137NS14
2 - De ´veloppe ´ a ` la seconde (HS)2,4
20.420 NS 15
3 - Arabesque roses (HS)2
0.489 NS7
4 - Arabesque sur la pointe (LS)5,6
0.155 NS12
5 - Pique ´ arabesque sur la pointe (LS)5
20.751
,0.029
Fairy of purity6a - De ´veloppe ´ a ` la seconde - Right Leg (HS)2
0.616NS8
6b - De ´veloppe ´ a ` la seconde - Left Leg (HS)2
20.605NS8
1Angular values for the analysed positions were averaged across judges prior to analyses; r=Pearson correlation coefficient; N=number of images available.
2HS=Highly Skilled postures: postures highly demanding in terms of balance (i.e. the ballerina is not supported by the male dancer) and/or motor constraints (i.e. leg
elevation above 90–120 deg).
3see an example in Figure 1 A.
4see an example in Figure 1B.
5LS=Less-skilled postures: postures less demanding in terms of balance (i.e. the ballerina is supported by the male dancer) and/or motor constraints (i.e. leg elevation
below 90–120 deg).
6see an example in Figure 1C.
doi:10.1371/journal.pone.0005023.t001
Changes in Body Posture
PLoS ONE | www.plosone.org5 March 2009 | Volume 4 | Issue 3 | e5023