Edited by:
Reviewed by: Katinka Dijkstra, Erasmus University Rotterdam, Netherlands; Xavier Corveleyn, Centre National de la Recherche Scientifique, France
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This article was submitted to Cognition, a section of the journal Frontiers in Psychology.
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Body sway while maintaining an upright quiet stance reflects an active process of balance based on the integration of visual, vestibular, somatosensory, and proprioceptive inputs. Richard Serra’s
Neuroaesthetics is an innovative and rapidly expanding research field, which currently champions non-invasive neuroimaging techniques as the research methodology of choice in the investigation of the neural basis of the cognitive and affective processes triggered during an aesthetic episode. These neuroimaging studies are principally directed toward the cortical and sub-cortical activations associated with producing or viewing pictorial art, listening to music, etc. Such studies revealed that various brain areas, such as areas belonging to the reward system (e.g., orbitofrontal cortex) or to emotional processing (e.g., amygdala, insula), areas related to high-level cognitive processes (e.g., prefrontal cortex), participate in aesthetics experience (e.g.,
Beyond these brain responses indicating that artworks’ observers can simulate creative processes, artworks can also impact the full body’s physiology. To evaluate such impact, posturography emerges as a field capable of providing novel insights into creative ideation, artistic creation, and aesthetic experience. By providing empirical data for theories of embodied cognition, posturography can potentially span multiple interrelated disciplines and bridge the gap between seemingly distinctive, physiology-related disciplines with their specialized and mutually exclusive focus on brain and body. Posturography quantifies aspects of postural control peculiar to upright quiet stance and it does so in a non-invasive manner across relatively short time intervals. It provides valuable information concerning the central nervous system’s ability to integrate multiple inputs (visual, vestibular, cutaneous, and muscle proprioceptive) and to generate muscular responses adapted as corrective torque by way of a feedback control system. The body is never perfectly still but is rather constantly in motion and physiologic body sway reflects these active processes. Posturography is mainly used in neurophysiology as a tool in the diagnosis and follow-up of patients suffering from balance and equilibrium disorders. Recently, two teams inaugurated this new field in aesthetics by questioning the effects of depicted body movements (
The present study pursues this innovative posturographic approach further by analyzing Richard Serra’s
The first hypothesis we made was that, as with other aesthetic stimuli displaying a strong sense of depth and movement, the mere observation of the sculpture would impact postural control. Such impact could be observed in either medio-lateral or antero-posterior direction as the sculpture involved strong depth (alignment of monumental solids in depth) and lateral (tilted monumental solids) components. Moreover, the effects were expected to be subtle, as the postural parameters would remain within the normal range for healthy young individuals.
In addition, artworks are never passively observed; rather, eye movement exploration is expected to participate in aesthetics experience. For instance, illusory movements while observing artwork from the Op Art movement could emerge from an instable eye movement behavior made of numerous small saccades (
Finally, we took advantage of our
In addition to posturography (Experiment 1), this study also introduces the use of the subjective visual vertical (SVV) test (Experiment 2), widely used since 1970 (
This experimental approach applies a novel methodology. The artwork being a unique stimulus within a unique museum environment, the results can only be compared to a basic measure (fixation of a cross, run before the visit of the exhibition). This study focuses on demonstrating the effect of this unique stimulus. This, however, does not imply that ordinary objects with similar physical properties would not lead to similar physiologic impact.
The investigation adhered to the tenets of the Declaration of Helsinki and was approved by the local ethics committee for human experimentation, CPP Ile de France II (No: 07035, Hôpital Necker in Paris). Written consent approved by the committee was obtained from all subjects after the nature of the experiment had been explained.
The primary stimulus employed in this study consisted of Richard Serra’s
During the exhibition, observers typically walked around and alongside the steel beams, taking in multiple viewpoints. Such behavior constitutes a unique aesthetic experience whose underline physiologic correlates form the object of this study. Indeed, one’s sense of gravity as well as both the visual and vestibular systems are challenged by Serra’s
Twenty-three young adults (26.1 ± 6.1 years) volunteered to take part in this experiment. Some of the participants came to the exhibition in response to an ad posted on a student mailing list and approached the experimenters at the entrance of the museum, while other participants were recruited directly at the entrance of the museum. None of the participants knew the hypotheses of the study.
Postural stability was measured using a posturography apparatus which consists of two dynamometric soles (TechnoConcept, Céreste, France), one for each foot. The excursions of the center of pressure (CoP) were measured during 51.2 s in each condition; the equipment contained an analog-to-digital converter of 16 bits. The sampling frequency of the CoP was 40 Hz. The duration of posturography recording is not standardized. While short durations (typically 30 s) are commonly used in clinics, longer durations might allow more discriminative power on non-linear parameters (
The participants were placed on the posturography platform along the central axis of the Grand Palais at 15 m from the first plate (see Figure
Condition 1 (basic): fixating a cross
When the participant entered the nave, before she/he had the opportunity to see the artwork, a 51.2-s posturography recording session was performed with the participant fixating the center of a cross (30 cm × 30 cm) located 30 m in front of her/him while turning her/his back away from the artwork.
Condition 2: fixating the sculpture
Immediately after the basic condition, the participant performed a 180° turn in order to face the sculpture directly. She/he was then instructed to fixate the upper right edge of the last sculpture as precisely as possible. Again, the posturography was recorded during 51.2 s.
Condition 3: eye navigation in depth along the sculptures’ transverse plane
In the next condition, participants were asked to fixate back and forth successively each sculpture from the farthest to the nearest sculpture repeatedly during the allotted 51.2 s recording period. Oculomotor behaviors of this kind necessitate saccade–vergence eye movements, which are a commonly observed class of eye movements executed during visual explorations of the environment (
The participants were then asked to walk freely both alongside and around the sculptures, thereby assuring that the subjects took in multiple points of view as would likely be the case had they freely visited the exhibition under normal circumstances. During this stage, they were listening to the exhibition audio-guide (tracks 102,103,104). The total duration of the
Conditions 4 and 5 (post visit testing): fixation and eye navigation
Following their
Data were analyzed using the following postural parameters: (1) standard deviation of medio-lateral and antero-posterior body sway (SDx and SDy); (2) surface of the CoP excursions, measured with the confidence ellipse including 90% of the CoP positions which were sampled by eliminating the extreme points (
A wavelet non-linear analysis using Morlet waves (
In order to test Hypothesis 1 (a first glance at the sculpture has an immediate effect on posture), we run one-way ANOVAs with the main factor SCULPTURE (fixating the cross before viewing the sculpture
In order to test Hypotheses 2 and 3 (exploration of the sculpture, with eye movements—Hypothesis 2—or during the
The one-way ANOVAs revealed that the SCULPTURE factor significantly decreased Px for
The two-way ANOVAs showed that the EYE MOVEMENTS factor significantly (i) decreased Py for F1 [
The two-way ANOVAs showed a significant interaction between the PROMENADE factor and the EYE MOVEMENTS factor for SDx [
The two-way ANOVAs showed that the PROMENADE factor significantly decreased Px for F1 [
The artwork was the same as in Experiment 1.
Fourteen new participants (29.5 ± 9.0 years) volunteered to take part in this second study.
In Experiment 2, participants were invited to visit the exhibition under the same conditions as in Experiment 1. The participants’ SVV was examined before and after visiting the exhibition with a dedicated device (Framiral, Cannes, France). The SVV was determined by inviting participants to stand in a dark room and adjust a luminous line to what they considered to be the earth-vertical axis. This test was carried out in an adjacent room of the museum where complete darkness was easily achieved. The reported error measures were absolute. To our knowledge, learning of the SVV task when examinations are performed tens of minutes apart has never been reported. Thus, any change in SVV errors can be reasonably attributed to the
In order to test Hypothesis 4 (the
Figure
In addition, examination of Figure
The first glance at these laterally tilted monumental sculptures causes a subtle decrease of the spectral power of medio-lateral body sway. We note the immediacy and specificity of this effect on body sway which is shown to occur along the same anatomical axis as the geometric axis about which the sculpture itself is tilted. This observation is in keeping with our previous posturographic analyses of paintings (
Testing the effects of visual exploration on postural control was primarily achieved by comparing fixation of the sculpture to eye movement navigation in depth along the sculptures’ transverse plane. As explained in Section “Materials and Methods,” the eye movements involved convergence and divergence eye movements, which were most likely combined with lateral and/or vertical saccades. Although eye movement recording was not possible, inspection of the subjects’ eyes by the experienced eye movement investigators clearly helped to confirm the occurrence of the aforementioned naturally combined eye movements. Subjects made approximately 15 back and forth excursions fixating the five sculptures successively one after the other. Such combined eye movements are in fact the most natural eye movements we make in real life to explore our 3D environment. The impact of such movements on postural control has not yet been studied. Instead some studies from our own research group have examined the effect of saccades and the effect of vergence along the median plane separately, using basic experimental stimuli such as fixating a cross or a laser dot that moves in depth. Saccades alone were not found to compromise postural stability and in fact some benefits were even observed (
In summary, whether or not these observations are specific to sculptures, this study demonstrates that moving the eyes across sculptures that are laterally inclined and aligned in depth modifies the control of body sway. Navigating Serra’s
Another major finding concerns the interaction between eye movements and the
The promenade decreased the spectral power of medio-lateral body sway. This was a major, subtle lasting effect that was significant for all frequency ranges. Again, this beneficial effect concerned the medio-lateral body sway, which was presumably related to the medio-lateral tilt of the sculptures. It has been demonstrated in laboratory studies that exposing healthy subjects to a tilted visual reference can cause a deviation in their body’s position (
Healthy subjects are able to perceive verticality with considerable accuracy and this faculty is dependent on inputs from visual, vestibular, proprioceptive, and somatosensory systems (
In this study, we found that the
Artworks in general are excellent opportunities to illustrate the theories of embodied cognition.
Visiting this exhibition involved emotional (e.g., facing the monumental sculpture within the Grand Palais’s neve), cognitive (e.g., listening to the audio-guide), and physiologic (e.g., observing this stimuli strongly playing with sense of depth and verticality, exploring it with combined eye movements and deambulation around it) processes. Ambulating within the sculpted environment of Serra’s monumental statuary work,
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The authors thank the administration of the Grand Palais, Paris, France, and the