Measuring Experiences of Art in the Museum

we measure the experiences of physical and VR art installations? How could that be done? The present research attempts to answer these questions through the use of a multimethod approach to assess every dimension of the experience of art. Wristband and questionnaires have been used as research tools to understand how the experience of art installations in the museum takes place and to study it

curator Franziska Nori for their shared goal of connecting the observers' bodies with the ones of the giant trees featured in both installations, in order to look for commonalities with other non-human fellow beings. Additionally, both these installations aim at evoking experiences of the sublime in the audience. Sensations, emotions, and thoughts, as well as physiological reactions and movements, partake in these experiences. Data collected with the presented methodology is potentially very rich thanks to the presence of original art installations (rather than their reproductions) over the space and time they are meant to be visited. Data from the questionnaires can be considered ecologically valid, as consisting of accurate subjective reportages of the visitors while actually experiencing the installations in situ. The proper measurement of physical and behavioral patterns is however harder to achieve as it relies on biometrics in a real-world setting. To overcome this issue and have more control over the multiple variables that can affect the measurements, a collaboration among disciplines and professionals from the art sector is at the heart of the matter.
Keywords: Virtual Reality, Art experiences, Ecological approach, Sublime. multisensory interaction and perception 1 . Artists can use miscellaneous materials to create art installations: traditional media (e.g.: painting, sculpture, natural objects, or man-made ones), new media (e.g.: film, animation, sound, audio), or mixed media.
However, regardless the material, what characterizes art installations is their enveloping nature. This type of art products is able to envelop the audience in their inclusive environment (space); to fully engage with an art installation, the audience is expected to have a unified experience of the designed environment with the content attributed to the work.
Art installations can emerge out of two different environments: physical and virtual.
The first refers to gallery-based spaces which are often an entire room or hall of a museum. The latter refers to digital or web-based spaces such as the ones created by Virtual Reality (VR, 360° technology, or panorama technology) 2 . The high levels of engagement evoked by physical or virtual art installations can culminate -in extreme cases -with the pure feeling of 'presence', a full immersion state that affects sensory impressions and awareness of observers. This could represent a plausible reason why art installations, specifically those designed through VR, seem to become more and more popular around the globe 3 . These moments of presence are characterized by an immediate sensitivity and they take place below one's absolute threshold for conscious awareness 4 . The audience is affected by art even before being aware of it at a conscious or linguistic level. Presence has been found to be an important characteristic in transcendent encounters that incorporate a sense of awe and sublime 5 . By transcendent encounters, we refer to those that «may be triggered via mechanisms in the brain, but the response lies in areas both more visceral and subliminal than those governing language» 4 . The empirical study of art installations is, therefore, still surrounded by many design challenges.

A multi-method approach for investigating experiences of art installations
The experience of art installations is a complex interplay of different factors. Art installations can evoke responses, ranging from a huge variety of subjective thoughts and feelings, combined with bodily changes and expressive behavior. We can therefore distinguish three dimensions of this experience: semiotic, physiological, and behavioral.
When experiencing an emotional event as the aesthetic one, the body is entirely engaged in a kinesthetic experience 6 because «the world we experience comes up at all times with our body as center, center of vision, center of action, center of interest». 7 For this reason, bodily changes (physiological dimension), as well as expressive behaviors (behavioral dimension), have been used as measures of embodied reactions from the audience in museum studies 8 . They can provide information on the autonomic nervous and visuomotor systems of our body interacting with the environment. Once these reactions are above our threshold of awareness, we are able to report our signs or thoughts about the perceived experience, our subjective feelings of emotions, and sensations (semiotic dimension) 9 .
The combination of measures for the semiotic, physiological, and behavioral dimensions of the experience of art -hereafter referred to as the multi-method approach -has until now been largely applied for the investigation of 2D visual art such as paintings 10 . Just recently, the interest in using the multi-method approach for studying art installations in an ecologically valid setting, such as museums, is growing. For instance, Tröndle, Kirchberg, and Tschacher 8 recorded body responses such as heart rate (HR) and standing patterns when beholding a physical installation in the museum and answered questions about whether the installation can be considered art or not. Overall, the studies that favored ecologically valid settings and focused on art installations have been found to have the following shortcomings. First, there has not been a study that achieves a full combination of all three dimensions of experience.
Physiological and behavioral data alone cannot provide insight into the semiotic states of the audience; thus, it is necessary to include self-report tools to tap into them. At the time of writing, studies by Pelowski et al. and Kühnapfel et al. were the only ones that took into account the complex emotional and cognitive aspects of the experience of art installations, although overlooking the meaning attributed (semiosis) to them. However, for a fuller understanding of the encounters with art installations, a broader range of physiological and behavioral measurements beyond eye tracking techniques could be included in their studies to determine how and why the experience of art installations develops across different areas of the body. It is essential to combine it with other quantitative and qualitative research techniques 14 to balance out the limitations of each method. For instance, eye tracking can show that a visitor spent more fixating time on a specific element of the installation, but it will not indicate the reason why this happened. On one hand, the visitor may have been fixating a specific element because they needed time to understand what exactly they were perceiving. On the other hand, they could have been focusing on that point out of amusement rather than mere confusion. It is important to combine mixed techniques to understand correctly the results. A combination of eye tracking with a HR monitor could allow, for example, for measuring the arousal of the emotion behind the experience as a plausible and physiological cause of the eye fixation. This would contribute to providing numerical evidence to the idea that the eye fixation occurred because of emotional processing. To discern whether that specific point of fixation evoked a positive or negative meaning, or a memorable reflection to the visitor, the research design should include tools for descriptive information such as self-reports and interviews. Hence, a more complete picture of the experience can emerge by adopting a multi-method approach.
Furthermore, as noted by the artist-researcher Sadia Sadia 4 , none of these studies included art installations with moving images and sound, soundscapes, or darkened environments. These elements, typical of contemporary experiential art installations, would presumably enhance the semiotic and bodily responses of the audience.
Additionally, the only study including the investigation of a virtual environment is the one by Gulhan, Durant, and Zanker 15 . However, it compares a physical art installation designed by an artist with a VR reconstruction which, although based on the same room design, was developed by the research team without artistic interpretation or intentions.
The study compared the experience of an art installation and its virtual reproduction in VR but it does not necessarily provide deductions about the experience of a VR art installation, therefore leaving the analysis of the features characterizing this type of exploration an open challenge.

Scientific and theoretical background: the sublime
VR can distort or extend the human perception, which is bounded by space and time, and, thanks to it, the audience can be thrown into spectacular sceneries. This allows the audience to experience, for instance, the magnitude of trees or the limitlessness of galaxies even in confined spaces such as a lab or the hall of a museum. 9 For this reason, VR has often been used for the scientific investigation of feelings of awe and sublime, elicited by nature.
Sublime experiences are indeed been largely associated with natural environments 15 . Sublimity can then be described by paradigm cases of natural objects or phenomena, possessing aspects at the limit of human imagination such as enormous size, great height, vastness, or tremendous power. These characteristics may result in the experience of an intense semiotic response (i.e.: subjective feelings and bodily sensations underlying emotional states). The emotions inspired by sublimity are often a mix of feeling overwhelmed, anxious, and physically small as well as exciting pleasure and admiration. 16 Moreover, the admiration felt during sublime experiences evoked by nature can induce the audience into a perspectival shift of self into other beings, leading them to potentially increase their respect for nature because of its new perceived qualities 17 . This theoretical standpoint moves away from Kant's human-centered sublime 18 , towards a more contemporary position of the environmental sublime.
Therefore, the feeling of the sublime is -among all the reactions that art can evokethe one that seems to deliver the strongest responses due to the formlessness of its experience. These reactions expose a connection to something physically and metaphysically grander than us, as nature can be. This aligns nicely with the vision at the heart of the exhibition and art installations selected for the present study in particular.
Sublime is intrinsically tied to emotions, imagination, and the sense of physical vulnerability of the audience 19 . Stamatopoulou, Lang, and Cupchik suggest that the sublime emerges as a «compact dynamic interaction» of a semiotic embodied experience towards evocative, yet not necessarily beautiful nor positive-valenced, stimuli. 20 The semiotic dimension of the experience of the sublime is characterized by a reflective engagement that might be given form and expression through a work of art, explaining why the sublime calls for art. That is, a subjective empathy reception process, where the individual feels increased self-reflection and self-awareness, as well as strong connectedness and closeness to the stimulus itself. According to Konečni, sublime-related experiences deeply move from within 21 . The physiological and behavioral dimensions of these experiences stand out for the responses of the audience of being physically moved, accompanied by (physiological) thrills and chills. Thus, movements and motion accompany sensations and emotions, and they are all at the core of transcendent experiences.
Although states of awe have been found to be frequently associated to the contemplation of artworks 22 , Brady argues that art is not fully capable of eliciting sublimity. 23 According to her view, paintings cannot easily deliver a real sense of sublimity as their form is physically constrained by frames and canvases. They

Methods
Empirical studies focusing on VR often have been using ad-hoc designed stimuli and experiences in the lab for control over the experimental setting 25 . This may have led to the study of a different kind of art experience, at least, quite different from the one of real artworks 13 in a real museum 26 .
To investigate the latter type of experience, this study used a pop-up lab in the Participants' experience has been measured via (1) a wearable device enabling us to capture physiological and behavioral data 27 , and (2) questionnaires to assess the subjective characteristics of the experience -namely, emotional state, bodily sensations, and feelings. The main purpose of this study was to explore a methodology to measure the experience of physical and VR art installations and how they differ or resemble each other in the semiotic, physiological, and behavioral dimensions. The proposed design will be described first, and subsequently analyzed and discussed. The discussion will unfold on three points: (1) exploration of its advantages and disadvantages; (2) its implications for future empirical aesthetics and museum studies; and (3) its relevance for answering questions of interests of art curators and fulfillment of the goals of artists.
The methodology outlined in the following pages, from the stimuli selection to the measurements taken, represents an effort of setting valid experimental conditions to investigate whether and how the media used for the creation of art installations constitute an influential factor in evoking transcendent art experiences involving sublime. This paper wants to introduce a more realistic approach that allows veracity of investigation of art experiences combining physiological measurements, behavioral ones, and questionnaires to detect objective and subjective information related to the way visitors interacted with the installations. Each of the methods employed is

Figure 1
Example of Experience Dashboard provided to the visitors who answered the questionnaire.

Participants
Visitors of the museum could voluntarily decide to participate in the data collection.
The recruitment has been advertised on the museum's website beforehand. All participants had normal or corrected to normal vision. Exclusion criteria were balance or vestibular disorders; severe heart diseases; severe cognitive deficits. The experiment was approved by the Ethics Committee Psychology of the University of Groningen

Art installations
The proposed study used two art installations present within the exhibition «The creating their installations, both of which will be described in more detail below.

Embalmed Twins I and II
Berlinde De Bruyckere's monumental double sculptures were born out of a discovery of two two-centuries-old oak trees that fell due to hurricane Cyrill in France in 2016.
Using wax, metal, epoxy, and textiles, the artist created two copies of the fallen trees and translated the emotion of seeing the power of natural forces into sculptural work (see Figure 2). 28    Installation view 31 and film still 32 of Treehugger: Wawona.

Procedure and measurements of experience
The present study was announced online and via mail, so visitors could sign up in advance to participate in the study. Besides, visitors were approached at the museum entrances. There were two options to participate in this study that participants could choose for their own: self-report tools may result in being intrusive to the user's experience since respondents must stop what they are doing (i.e.: the art experience) to perform the task, they enable respondents to a quick, intuitive, and accurate subjective reportage.
The basic questionnaire includes the following self-report tools (see a, b, and c in Figure   4 with artworks in museum studies 41 . In the present study, the GEW will also represent a way to assess whether there is a correspondence between the media used to create the installations and the emotions that the viewers reported.
3. PSS is a pictorial self-report that people can use to rank how small or great they felt. Visitors were presented with seven circles and asked to select the one that best fits their perception of self-size. This tool is aimed at measuring the feeling of diminishing of the self, or small self, usually associated with feelings of transcendent emotions. 42 In addition to the tools presented in the basic questionnaire, participants could decide to answer questions from the extended questionnaire regarding their own thoughts about the installation and the connectedness felt with it (see d, and e in Figure 4). (1) What was the installation about? and (2) What does the installation mean to you? The response was required to be at least 30 characters.
2. Lastly, participants could answer two adapted versions of the ICSS. ICSS is a single-item pictorial tool to measure how people feel interconnected with something. In this study, the first ICSS was used to measure the relationship between the participant and the installation, and the second ICSS measured the relationship between the participant and nature after having experienced the installation.

Figure 4
Self-report tools used in the questionnaires.

Physiological dimension
Physiological activities and expressive behaviors have few advantages such as (1) continuous measurement in real-time; (2) no intrusiveness for the user, and (3) no bias from cognitive or social desirability constraints 43 . To access the visitors' changes, at a physical and behavioral level, while experiencing the art installations, the current methodology relied on the use of Empatica E4 Wristband. Visitors could voluntarily wear the Empatica E4 Wristband for real-time physiological data acquisition.
Participants that wanted to wear the Empatica E4 received them at the entrance of the installation areas upon administration of informed consent. After the experience of the installation, they could return the device to the researchers. Empatica E4 is a wrist-worn research wearable that has Electrodermal activity (EDA, also known as galvanic skin response, or GSR) electrodes, a temperature sensor, and a photoplethysmography (PPG) to record autonomic nervous systems (ANS) parameters such as heart rate (HR), blood volume pulse (BVP) and interbeat interval (IBI). These parameters have been associated with emotional responses and Empatica E4 has previously been validated as a reliable emotion recognition tool outside laboratory 44 . The collection of physiological data via Empatica E4 aims at answering the research question regarding the comparison of bodily changes across the different types of art installations (i.e.: physical and VR). The methodology adopted in the present study aims at integrating more physiological measurements than previous literature to give more granular results of the understanding of art experiences.

Behavioral dimension
While the physiological dimension could be measured by EDA, HR, and temperature recorded by the Empatica E4 Wristband, the behavioral dimension was assessed

Exploration of advantages and disadvantages
Art installations can trigger transformative changes at the semiotic, physiological and behavioral dimensions. However, drawing empirical evidence from these three experiential dimensions is a complicated matter. First of all, multidisciplinary conversations of the research team led to the conclusion that, to tap into the experience of art installations, empirical evidence cannot be collected by measuring how participants respond to a reproduction of an artwork in the laboratory. We wanted to take into account the complex nature of art installations and that participants' reactions to it are also tied with the time and space in which the experience of art installation takes place. The encompassing environment in which art installations are framed is thought to impact the audience's reactions. 7 For this reason, it is important to conduct field observations to investigate the experience of art installations, that is to carry out empirical research in an ecologically valid setting such as museums, as presented in the proposed methodology. Studies in the laboratory «will never achieve scientific certainty. They will be based on observation rather than on experiment; and they will remain, for that reason, conjectural and suggestive». 50 The use of a real-world setting enables the visitors' most insightful behaviors that would be otherwise subdue in laboratory settings. 51 However, it is hard to bring research tools such as MRI tables, into a museum and, even, if possible, their implementation can result to be invasive of the visitor's experience at the museum, ending in affecting it.
The presented research also attempted to design a methodology that would alter the experience of visitors with the installation as little as possible. For this reason, the wristworn Empatica E4 was considered a suitable choice. Firstly, it is the only wearable on the market granting access to raw data of the combined sensors that simultaneously measure sympathetic nervous system activity, movements, and heart rate. These measures can capture the process that dynamically changes over time while experiencing the art installation. Secondly, among all the wearable devices, wrist-worn ones are commonly used by laypeople. Suffice to think about how smartwatches are frequently worn as physical fitness monitors, pedometers, monitors for quality of sleep, and so on. In addition, wrist-worn devices are not very noticeable, nor heavy and they are not particularly visible to others. All of these features contributed to not disturbing the visitor's experience of the installations but rather revealing spontaneous behavior 52contrary to the one under the influence of cameras rolling, or while wearing An obvious limitation of using biometric techniques in the museum is that there is a wide spectrum of factors (individual, social, and environmental) that may influence the measured patterns. On one hand, testing biometrics in the museum may be challenging as variables cannot be carefully controlled. On the other hand, the semiotic dimension assessed by questionnaires can only benefit from such complexity. The results from the questionnaires could reflect the true semiotic experience of each visitor toward the two physical and virtual art installations. This is because the experience was not merely reproduced in the laboratory, but fully present.
To sum up, the data detected by the presented methodology are potentially very rich as we ensured the presence of original artworks in the space and time they are meant to be visited. This rendered the data from the questionnaires ecologically valid and representative of the true experience. However, the proper measurement of physical and behavioral patterns is harder to achieve as it relies on biometrics in a real-world setting. introspection. 53 According to Lee, this reflection allows a heightened experience where people can perceive their affective responses, mental notes, and bodily accompaniments without interrupting the process of perception but rather leading them towards an epiphanizing experience of art.

Implications for future empirical aesthetics and museum studies
By detecting the body's passive responses, active movements, affective feelings, and thoughts of the audience in the museum, the methodology explored can help researchers in their systematic study of arts and aesthetics in the light of theories of embodied cognition, motor and kinesthetic psychology, and Einfühlung (empathy) 54 .

Relevance for answering questions of interests of art curators and fulfillment of the goals of artists.
Inspired by Wiseman and colleagues 55 , the present study established a collaboration between researchers with backgrounds in humanities, psychology, and art curation. This helped in designing the experiment in a way that could answer multidisciplinary questions. While the empirical results will be presented in multiple-cases analysis to assess the methodology's validity in a separate instance, we will hereby provide examples of the usefulness of the methodology in terms of the potential discovery of the experience of art installations in the museum, and the difference in terms of experiential dimensions among physical and Virtual Reality (VR) environments for art installations.
As Hume states, one's perceptions of their internal and external senses are «clear and evident». 56 The use of BSMs can then be a reliable method to further explore the dialogue between the body of the audience and the material used for the art installations. Sublime experiences are intimate and hard to be precisely defined by exact words, and art experiences, in general, are not exclusively mental. Therefore, in conjunction with emotional and evaluative aspects of the semiotic dimension described by subjective reportage, we should capture and consider the way the body reacts in the environment.
Vischer conceptualizes the centrality of the body and its relationship to experience by stating that «the whole body is involved; the entire physical being is moved». 59 Similarly, Vernon Lee defines the importance of one's physical corporeal responses and motor actions during experiences of art as it is impossible to clearly distinguish mind and body in such experiences. 60 Therefore, to capture the process of the experience as it happens, we should also detect how it is perceived by our bodies. In the present instance, our multimethod approach can potentially analyze the differences in physiological and behavioral responses between different instances of art (e.g., the physical and the virtual) and attempt to describe the relationship between sublimity and movement.
Research outcomes concerning the relationship between the three dimensions of art experience can provide support to the decision-making process for the curatorial work. That is, art curators can use the findings to make evidence-based choices and strategies about the use of exhibition space to achieve a specific, desired effect. Further, the multimethod approach can also attempt to answer questions based on the artist's intentions, such as, in this specific case, whether an empathic transference of the self to another non-human being does take place through the appreciation of the art installations. The emotional experience (constituted by bodily changes, sensations and semiotic modes) triggered by the art installations may establish cognitive insight that can favor a sense of community with the natural elements subject of the installations.
The results from the Inclusion of Community in Self Scale (ICSS) can be used to assess which type of installation generated stronger feelings of communion with nature. That is, based on the hypothesis that art installations, both physical or virtual ones, can help the user overcome the limitations of their own human body to empathize with those trees. However, in order to put the present methodology to the service of artists and reach practice-based evidence, it would be advisable to involve the use of expertise from the artists themselves. Researchers should take into account the artists' statement about their work and the way these may affect the audience. The outcomes resulting from the presented methodology can support the art-making process for an optimal impact and delivery of the artists' intentions. That is, the study of art installations can be beneficial for artists. They can receive feedback from the target population to which their work is directed to, attest the impact and overall effect of their work on the audience, and verify whether it aligns with their intended message. Future research could improve by personally including the artists in the early stage of experimental designing.
The exploratory methodology used in the present study aims at constituting a starting point on which to build a corpus of reference. It is valid in the exploration of in situ experience of art installations and can be replicated in future studies to address its usability in different contexts (such as the experience of paintings, music, performance art, and various art spaces).

Conclusion
The present paper wants to encourage future research in using a multi-method approach as it can help gain a full understanding of the data on multiple dimensions. The explored methodology has the potential of providing highly informative findings that can be relevant to different disciplines and professionals -from researchers in empirical aesthetics to experts in the curating process. For this reason, it is important to stimulate the dialogue between researchers, institutions, and artists for them to benefit from the research outcomes.

Acknowledgments
Data collection support was made possible by the staff of the Frankfurter Kunstverein.
We also would like to thank Alice Barale, Claudio Rozzoni, Ryan Joseph Slaby, Anna De Martino, and Marco Franceschina for their philosophical expertise and useful discussions.