Our built heritage forms a unique asset, as it expresses the richness and diversity of our common past. Heritage sites and monuments should therefore not be interpreted just as physical constructions, but as tangible artefacts that represent meanings and values that might even change over time. We therefore consider how the built heritage can be interpreted as a communication process [1
], in which the different types of values and meanings can be perceived, understood and appreciated by a wide range of visitors. Typical values and meanings that originate from built heritage include factual and explicit meanings, such as shapes and forms, which are relatively easy to be graphically represented via text or images. Likewise, dimensions, which synthesize the proper understanding of the built heritage, are commonly communicated via drawings and sketches. Yet more intangible or tacit meanings and values, such as the skills, ideas and experiences that the heritage represents, are typically more challenging to communicate to visitors due to their implicit and often abstract character. Yet such tacit knowledge is particularly important to understand the complexity and richness of heritage as an experiential and communal concept that is not necessarily declarative or definitive. Tacit knowledge of built heritage includes, but is not limited to: (a) architectural qualities, such as how aspects of the work reinforce the oeuvre of a known or distinguished architect, the interrelationships of the different design styles within the artefact, the contributions to its environment, or particular structural or decorative aspects and their design process [2
]; (b) cultural values, such as how the work has gained cultural significance with the passing of time, or how particular building characteristics illustrate specific societal developments; (c) aesthetic features, such as how the work corresponds to the sense of tradition and is manifested through an appreciation of cultural and historic characteristics [3
]; or (d) symbolic significance, such as the symbolic aspects of what the work represents, or their embodied value in terms of their construction [4
In particular, our research focuses on communicating tacit knowledge of built heritage. We are motivated by the emerging concept of heritage democratization [5
], which states how communication forms a crucial matter in heritage, as an exceptional vehicle for spreading knowledge and heritage values by collectively facilitating access and awareness for extended protection [6
]. By democratizing its communication beyond heritage professionals for conservation decisions [7
], the significance of this tacit knowledge can be appreciated by a broader public such as to raise community awareness or to enable heritage visitors to appreciate heritage in more experiential ways.
During the past two decades, several emerging digital technologies already profoundly influenced the ways of disseminating and communicating cultural heritage [8
]. These technologies vary in terms of their modality, immersion and integration into the physical manifestation of the heritage environment. For example, digital audio-guides in museums now offer immersive sound atmospheres that enrich the exploration of museum collections. Although these audio guides can be synchronized with individual trajectories [9
], their individual “audio bubbles” [10
] tend to isolate users insofar that they may hinder social or natural interactions between visitors themselves. Other technologies like digital displays focus on the communication of heritage values and meanings via the graphical user interface (GUI) such as via hand-held devices providing digital storytelling [11
]; via large and sometimes interactive displays or multi-touch tabletops [13
] that present textual or graphic heritage information, allowing multiple people to comprehend information and even enable the interaction of multiple people simultaneously, fostering different forms of socialization between them [14
]; or even more flexible active presentation modalities, such as projections [15
] that are able to engage multiple museum visitors in more body-centric and thus physical ways.
Tangible interaction is an interdisciplinary field of research, spanning a variety of perspectives, including Human-Computer Interaction (HCI) and Interaction Design. Its research tends to investigate how computational and mechanical advancements can be combined to allow novel forms of natural manipulation and full-body interaction with data and information [16
]. In comparison to GUIs, tangible user interfaces (TUIs) are believed to be relatively more intuitive, as TUIs tend to communicate meaning through their physical affordances [17
], such as by mapping information into physical shapes and forms, or into its material attributes (e.g., size, shape, texture, color, weight). Because of these affordances, which reveal the implied interaction possibilities through the physical design features in apparently seamless and natural ways, TUIs tend to require little experience or skills to be operated, and can function as both input and output mediums [18
]. TUIs have also shown to possess significantly different qualities in comparison to commonly existing ways of heritage communication. For instance, TUIs tend to perform better in terms of recall because it requires multimodal ways of human perception to discover and decipher their meaning [19
]. TUIs differ from touch surfaces in terms of their positive suitability in supporting collaborative and participative processes among users [20
], while their explicit touch and manipulation affordances have shown to attract more visitors towards more extensive forms of exploration during interactive exhibits [21
]. The design of TUIs focuses on how tangibles represents digital information and how it empowers users to interact with this information [22
]. This information is often represented by metaphoric [23
] or symbolic [24
] forms via interaction modalities, which we call ‘navigation’ later in this paper. Because of these unique qualities, we believe tangible interaction forms a promising paradigm for communicating tacit knowledge of built heritage.
In fact, tangible interaction has already been scientifically investigated as a potential means to communicate different forms of heritage information. For instance, the European project meSch (mesch-project.eu) focuses on enabling forms of co-design between designers and heritage professionals by way of a do-it-yourself philosophy of making and experimenting. Recent outputs of this project include for instance, a book-like device that visitors carry with them during their visit in an outdoor heritage environment to support storytelling, as location-based auditory information is played when a magnetic bookmark is placed on a selected page of the book [25
]. In museums, 3D printed replicas of original artifacts are used to trigger digital narrative content projected on museum display cases [26
TUIs offer a spectrum of opportunities for museums with regard to the level of embodiment, focus of interaction, and targeting specific audiences to communicate the tangible and intangible values of heritage. First, applications of TUIs in museums vary in terms of how the museum artifact is embedded in the interface; from using the original artifact itself as an interaction device, such as triggering illuminations and auditory information by touching the artifacts [27
], to a semi attached interaction, such as using a wooden magnifying lens with an integrated smartphone for allowing visitors to examine museum artifacts by pointing the lens close to them and then extra digital content (e.g., text, images or animations) is displayed on the smartphone [28
], to more detached interaction when the original artifact and the interface are located in distant places in the museum for provoking visitors’ curiosity to visit the artifact and to learn about it [29
]. Second, communicating information and values of cultural heritage through tangible interaction could be explicitly integrated into sensorized objects by focusing on their physicality [30
], or it could be implicitly integrated in a gesture or an action, focusing therefore on the act rather than the object itself [31
]. By performing specific actions, the visitor implicitly understands and experiences an intangible value related to a certain object. These actions could be performed to navigate 3D models, to compare several objects, or to experience the physical material properties of an object [29
]. Further, the tactile qualities of tangible interaction allow for interactive installations in museums that target specific audience [29
]. For instance, the mix of materialities encourages creativity for playful exploration and allows for educational opportunities in a children’s exhibition [32
]. Moreover, the tactile exploration enables blind and visually impaired people to interact with heritage collections by touching specific hotspots on the artifact [33
], or by navigating 3D surfaces via a smart ring in their fingers [34
] to trigger voice explanations.
However, little is known on whether and how tangible interaction is effective in communicating knowledge or meaning, let alone in the context of revealing tacit knowledge of built heritage in a museum context. In order to investigate this issue and to benchmark different tangible interaction and feedback modalities, we conducted a between-group comparative study in a real-world museum context. As tacit knowledge, we chose a particular story that relates the physical and architectural characteristics of the entrance colonnade at the Djoser Complex in Saqqara to the potential meaning of the historical journey along the Nile in ancient Egypt. We investigated how this symbolic significance and other architectural qualities were communicated to museum visitors based on their interaction with three different experimental conditions. We also examined their engagement during interaction and how it affects communicating tacit knowledge of built heritage. Each of the tested experimental conditions consisted of an interactive navigation (input) and a passive representation (output) components. As such, the three conditions differed from each other by one of the tangible modalities, ranging from a traditional digital display interface to fully tangible means of interaction.
Most ancient Egyptian antiquities are characterized by tacit knowledge like historical values as well as distinctive architectural qualities, which all predominantly represent symbolic significance through association and context. We chose to communicate the tacit knowledge of the Djoser pyramid complex in Egypt specifically because: (a) the antiquity department at the Royal Museum of Art and History in Brussels already possessed significant historical and archeological expertise of this particular site; (b) we discovered that its architectural layout and features are comprised of a rich variety of distinctive architectural qualities that could potentially be represented via tangible interaction, such as its spatial proportions, number and style of columns, etc. which individually (c) symbolize a specific historical story that is sufficiently compelling and interesting to be communicated to a large, lay audience. As such, our study was deployed in close collaboration with the Antiquity Department of the Royal Museum of Art and History in Brussels. The museum possesses the largest collection of Egyptian antiquities in Belgium, including a monumental scale model of the Djoser pyramid complex in Saqqara that dates back to 1943. The fabrication of this scale model was managed by the Egyptologist Jean-Philippe Lauer, who considered Saqqara as a life-long commitment [35
]. Although the model was not publicly accessible at the time of our study, it might be featured in future exhibition designs, so that the empirical knowledge from our studies could form a foundation on which future tangible interaction approaches could be grounded.
The Djoser pyramid complex forms a mortuary precinct in Saqqara believed to be designed by Imhotep, one of the greatest known architects in ancient Egypt [36
]. It was built for pharaoh Djoser around the mid-27th century BCE, and is recognized as the world’s oldest large-scale stone structure. Its entrance colonnade consists of a limestone ceiling, loaded by pairs of limestone fluted columns composed of drum shaped segments, all reaching a height of 6.6 m. The columns are not free-standing, but attached to their side wall by masonry projections, hereby composing 42 individual niches
, which are the spaces created between adjacent columns (Figure 1
, right). The combination of complex architectural features of this impressive entrance colonnade carries a peculiar cultural meaning, as its particular physical layout can possibly be associated to the historical journey the pharaoh undertook along the Nile to visit each of the 42 nomes
, the administrative territorial divisions of ancient Egypt (Figure 1
, left), and their local gods. Some Egyptologists propose that each niche
in the entrance colonnade represented a shrine where the nome
gods of ancient Egypt were accommodated during the Heb-Sed
, a festival celebrating the continued rule of the king through rituals that symbolically rejuvenate him [37
], for opposing views see [38
]. This working hypothesis is believed to be plausible because the number of niches
are equal (42). As such, the architect Imhotep may have designed the architectural layout of the colonnade to portray symbolically the Nile River, and consequently the end chamber would represent the Delta region.
In short, the historical hypothesis is that the processing of pharaoh Djoser along the corridor, passing by each nome
shrine, represents and evokes a ritualized version of the pharaoh’s journey along the Nile to visit each of the nomes
and their local gods [39
]. Our study hypothesis is that this tacit historical knowledge can be effectively communicated via tangible forms of interaction, which will lead to more collaborative forms of interaction and more profound recall of tacit heritage qualities by general museum visitors.
The final comparative study involved a total of 42 participants, almost evenly distributed over the three different conditions (13 Touch-Dix, 14 Tang-Dix, and 15 Tang-Phys), who participated individually (10) or in groups (32), including couples, friends, or parents with children on a family museum visit. Only one group composed of two visitors do not know each other who socially engaged only in the sake of participating in the experiment. Participants varied in terms of gender (i.e., 4 males, 14 females, and 24 mixed groups of males and females), age range (i.e., children, teenagers, adults, and elderly), and the purpose of their museum visit (i.e., 2 school or university visits, 13 family visits, 13 local tourists, 13 international tourists, and 1 museum staff member). Based on the observations, interviews, and the user experience questionnaire, our findings are categorized into aspects relating to the communication of tacit knowledge and the user engagement.
4.1. Communication of Tacit Knowledge
This section describes how differences in the navigation and representation features of TUIs impact its ability to communicate tacit heritage knowledge in a museum context, including its symbolic significance and architectural qualities.
4.1.1. Comprehension of the Symbolic Significance
Our results indicate that the level of understanding of the symbolic relationship differs between the three conditions. In Touch-Dix, 39% of the participants (5, N = 13) immediately mentioned the link when they were asked about what did they learn from interacting with the installation, e.g., “I think I was quite fast in understanding that link … for me, it was quite clear” (participant 18). Another 39% of the participants (5, N = 13) described the link when they were asked more specifically during the interview about the corridor’s symbolic representation. The remaining participants (3, N = 15) considered it difficult and commented on its complexity after it was explained to them “you see a corridor and a lot of pillars, but to link it to the Nile is too far” (participant 21).
Condition Tang-Dix proved more challenging, as there were only 3 participants (N = 14) who mentioned the symbolism immediately when they were asked what they learned from their interaction. However, participants found this insight not easy: “I was moving this control (statue) through the river, and at the same time I was thinking why I am moving on the river, it was not related to the display … I think it is not easy to make a connection” (participant 6), whereas 5 participants (N = 14) in the Tang-Dix condition only described the meaning during the interview when they were asked more specifically about the corridor’s symbolic representation. For instance, “if you only put this in front of visitors, nobody will get it” (participant 11).
In contrast, condition Tang-Phys
succeeded better in conveying the symbolic significance as 14 participants (N = 15), of which 10 in graspable
sub-condition (N = 10) and 4 in fixed
sub-condition (N = 5), mentioned the symbolic meaning when they were asked about what they learned from their interaction: “it was evident when we are moving, the light is moving, so it was the Nile. As the Nile is the spine of Egypt, then it is Egypt”
(participant 27). Participants noted that they gained this knowledge only by interacting with this condition, as “I did not know it was represented by the building. Now, because I saw the lights, I understand why the building was built”
(participant 30). Some participants reflected even upon the larger context of this insight. For instance, in Tang-Phys
condition a participant mentioned that “it was clear that this building was [built] at a unification period”
(participant 27), as he linked the story to the ancient Egyptian history when Egypt was divided into two regions, a historical fact that was also illustrated in the informative poster (Figure S1
With regard to prior experience, we had 10 participants who previously visited the Saqqara site, as indicated in Table 2. Our results show no direct effect on the intuitive understanding of the symbolic meaning of the story (i.e., none of them from Touch-Dix (N = 3), only one from Tang-Dix (N = 4), and 2 from Tang-Phys (N = 3)). Further, it was challenging to extract the age-related differences regarding the understanding of the symbolic significance, as for instance all children visitors participated in groups with adults or elderly. Among groups with children, 3 groups intuitively understood the meaning from Touch-Dix (N = 4), 1 from Tang-Dix (N = 2), and 3 from Tang-Phys (N = 3). We noticed that the role of interacting with devices was dedicated mostly to children, while parents were focusing more on the poster and the map to understand the meaningful relationship; e.g., a parent from Touch-Dix condition: “I was looking at the image (poster) and the map, not at the 3D model” (participant 42).
4.1.2. Communication of Architectural Qualities
Participants described the colonnade as a linear space with a large number of columns and unclosed chambers between them (niches). When they were asked to estimate the number of the columns in the corridor (44), their answers in digital display conditions (Touch-Dix and Tang-Dix) were relatively correct, estimating their number as (53, avg.; 45, median) in Touch-Dix condition, and (51, avg.; 50, median) in Tang-Dix condition. However, in condition Tang-Phys, they tended to overestimate the number of columns (69, avg.; 49, median).
● Spatial dimensions and proportions
The participants’ perception of the length of the colonnade varied from the actual length (56 m) to relatively large overestimations towards hundreds of meters. The average and median of their estimations per each condition were calculated and listed in Table 2
. The average in the conditions of digital representation was quite convergent; 187 m in Touch-Dix
and 162 m in Tang-Dix
(medians are 150 m, and 75 m respectively). In Tang-Phys
condition, the average of their estimations was 308 m because of a few outliers (median is 100 m). Although most participants initially hesitated to sketch the colonnade’s dimensions on the grid paper due to a sense of social embarrassment or self-perceived poor drawing skills, all participants eventually sketched the requested section of the colonnade (Figure 5
). Some of them even voluntarily used this opportunity to depict specific details, such as the ceiling’s levels (Figure 6
b) and the fluted columns (Figure 6
c). Participants varied in estimating the height from approximately double the standard floor height, which is relatively correct (6.60 m), to somehow overestimations till 12 m in all conditions. However, their perception of the width varied between the digital representations conditions to the tangible scale model, as indicated in Figure 5
and Table 2
. The estimated width in Touch-Dix
conditions corresponded well with the actual internal width (i.e., inside) of the colonnade, whereas in the Tang-Phys
condition, the external width (i.e., including the width of the outer walls) was perceived instead, as illustrated in Figure 5
. Moreover, we calculated the width-to-height ratio in order to evaluate participants’ perception of the proportional relationships of the space instead of absolute values of dimensions, as people tend to perceive spatial dimensions improperly through digital displays because of the limited field of view [43
]. As such, we discovered that the ratio estimations conformed to the previous results, as illustrated in both Table 2
and in Figure 5
Since spatial estimations seem to vary significantly between participants, making potential generalizations from these results is complex. Even in a group of multiple participants there existed different estimations of the spatial dimensions (e.g., Figure 6
a). For the more traditional digital representations, some participants perceived the steps of the ceiling (e.g., Figure 6
b), an observation that did not occur in Tang-Phys
as the physical model was fabricated as a cross-section of the building, having no ceiling.
● Shape, color and materiality of columns
In the digital representation conditions (i.e., Touch-Dix
), most participants (22, N = 27) correctly described the columns as having a rounded shape. Moreover, 10 participants (N = 13) in Touch-Dix
condition and 8 participants (N = 14) in Tang-Dix
condition mentioned that the columns were not smooth, but were fluted with vertical grooves. In condition Tang-Phys
, some participants (5, N = 15) thought that the columns had a square or a rectangular shape, a perception that might well be the result of the top view that highlighted the square caps rather than section of the columns. “Normally, columns in ancient Egypt are cylinders, but these are not. They were made of lines and angles. I even have the impression that they are not circular. But now thinking logically, I haven’t seen any rectangular columns, they are always kind of circular, although the upper part (cap) could have been rectangle or square”
(participant 27). However, 9 participants in Tang-Phys
condition (N = 15) mentioned that the columns were rounded and fluted, with one participant even drawing a detailed view of this flutedness as shown in Figure 6
c. It is worth mentioning that within the graspable
sub-condition of Tang-Phys
, 7 participants (N = 10) perceived the flutedness of columns, while only 2 participants (N = 5) perceived it in the fixed
Participants also perceived other architectural qualities, such as the color (i.e., beige) and the materials (i.e., sand stone) in the digital representation conditions. However, as those qualities were not readily visible in condition Tang-Phys as the scale model was fabricated as a white, monotonous sculpture, we do not consider these for further analysis.
4.2. User Engagement
This section describes the engagement of users in terms of their apparent focus of attention during interaction, their replies on the user experience questionnaire, and their forms of engagement and appreciation.
4.2.1. Chronological Analysis
Participants focused their attention on varying aspects during the interactive exploration process of each condition. Figure 7
demonstrates the chronological analysis of the three conditions, each row in the figure maps the interactions of a single participant along a horizontal timeline. Consequently, more yellow (i.e., focus on representation) can be noticed in condition Tang-Dix
, while the green color (i.e., focus on navigation) can be noticed more during the interactions with conditions Touch-Dix
. These patterns denote that condition Tang-Dix
encouraged participants to focus more on the representation element (digital display), while the other two conditions (Touch-Dix
) allowed participants to distribute their attention on both the representation (i.e., the digital display and 3D physical rendition) and the navigation (touch screen and tangible installation) elements. Moreover, we found a correlation between the visual attention of participants and their understanding of the cultural knowledge. As participants’ focus of attention in Tang-Dix
was less on navigation, and more on the digital representation on the screen (Figure 7
condition attained the lowest percentage of understanding the story as indicated in Table 2
. In contrast, the simultaneous focus of attention between navigation and representation in Tang-Phys
resulted in better understanding of the symbolic significance of the colonnade.
Although all three conditions had the attention of a relatively similar number of participant groups (i.e., 12 in Touch-Dix (N = 13), 10 in Tang-Dix (N = 14), and 10 in Tang-Phys (N = 15)), the social interaction between the participants themselves was more noticeable during condition Tang-Dix. In contrast, there was somewhat less interaction in condition Tang-Phys, while in condition Touch-Dix the social interaction between the participants was much less than with the other two conditions.
4.2.2. User Experience Questionnaire (UEQ)
All UEQ items are scaled from −3 (representing the most negative answer) to +3 (representing the most positive answer, when 0 is a neutral answer). The Alpha-Coefficient value showed a high consistency for the items of attractiveness, stimulation, and novelty scales in all conditions. In contrast, the value was lower than 0.7 for the perspicuity scale in Touch-Dix
, in efficiency scale in Tang-Dix
, and in dependability scale for all conditions, meaning that these questions were probably misinterpreted or interpreted in a direction that does not reflect the intention of the participants within the context of UEQ [44
As shown in Figure 8
, the three conditions were statistically compared on the basis of the means for each UEQ scale. As the differences between the conditions are not significant for each of the scales (p
-value is >0.05 in t
-test), statistically valid generalizations are impossible. However, the results might still demonstrate some tendencies and trends in how each condition performed. For instance, Tang-Phys
is more positive in attractiveness, perspicuity, efficiency and dependability scales, while Tang-Dix
shows a positive performance in stimulation scale, and Touch-Dix
in novelty scale.
4.2.3. Engagement and Appreciation
In general, individual participants spent less time interacting (133 s, avg.; 85 s, median) in comparison to groups of participants (195 s, avg.; 180 s, median), as the discussion between group members encouraged them to explore the installation more. When comparing the different conditions, participants spent more time in case of tangible navigation; i.e., Tang-Dix (182 s, avg.; 165 s, median) and Tang-Phys (180 s, avg.; 160 s, median), compared to Touch-Dix (179 s, avg.; 130 s, median).
While the UEQ results demonstrate no significant differences between the conditions for all of the UEQ scales, participants seemed to have interpreted and appreciated the conditions differently. For instance, the concept of gaining new knowledge was mentioned 7 times in the context of Tang-Phys
condition (N = 15) “I like it because I learned something new”
(participant 38), and the concept of interactive experience in museums was mentioned 4 times in the same condition “actually I like this installation very much because it is smartly done”
(participant 33). The condition Tang-Dix
seemed less appreciated by participants (Figure 9
), as 7 participants (N = 14) thought it required more explanation to be more appreciated, “if you have explanation on the side, it may be clear”
(participant 12) and “I like it now when you tell me the story, but before … not”
(participant 7). We have the impression that participants seemed to even less appreciate the Touch-Dix
condition (Figure 9
), mainly because of the lack of immersion when looking at the 2.5D representation of the colonnade “it was too simple to grab my attention, and I was not immersed in it”
(participant 42), and possibly because they felt a bit frustrated “oh, we tried every direction, and we see only columns”
In this section, we discuss the implications of our findings from this study with relevance to future research or potential further development of communicating heritage via tangible interaction. On the whole, one could note that Touch-Dix participants estimated the spatial features like dimensions (i.e., internal width) and quantity of major architectural elements relatively well. The condition Tang-Dix was better in stimulating social interactions among participants, who focused more on the output medium. Finally, the results of Tang-Phys show that it was better in conveying the symbolic significance of the colonnade, and it was more positively judged in the UEQ. Participants in that condition were more accurate in estimating the external width of the colonnade. In the graspable sub-condition, many perceived particular physical characteristics, i.e., the flutedness of the columns.
5.1. Role of Navigation
The design of our installations defined a new vocabulary of actions (e.g., similar to [26
]), and the visitors were required to perform these actions in order to achieve certain goals (i.e., capturing the cultural knowledge). All three conditions were specifically designed to communicate the same tacit heritage knowledge by allowing participants to construct a meaningful link between an interactive navigation and the dynamic representation. Yet we observed that the actual effectiveness of linking and sense-making depended on the cognitive effort required to operate the tangible interaction interface, which consisted of the simultaneous use of an input (navigation) and output modality (representation). More specifically, the touch display in condition Touch-Dix
proved harder to discover and then to operate, particularly when combined with a visual-centered output modality. We observed that the touch display affordance was mainly provided via the navigation component, while the visual attention of participants was constantly required in order to observe the relative position of their finger on the map, displayed on the screen (i.e., flat glass surface). In contrast, moving a physical object (i.e., the 3D printed statue of the pharaoh) along a groove possessed sufficient intuitive affordances and tangible guidance so that most visual attention could be dedicated to the output modality (representation) in Tang-Dix
Accordingly, we believe that an equilibrium needs to be sought between the affordances and cognitive effort required when combining tangible interaction navigation and representation modalities. As participants’ focus of attention in Tang-Dix
was less on navigation, and more on the digital representation on the screen (Figure 7
condition attained the lowest percentage of understanding the story as indicated in Table 2
. In contrast, the seamless integration of navigation and representation in Tang-Phys
resulted in better understanding of the symbolic significance of the colonnade. For instance, participants were able to do two simultaneous actions; tactile navigation and bringing their eyes to eye-level in the scale model (Figure 10
c). This was possible because the two actions are relatively usable and not requiring visual focus. The link between navigation and representation could cause a sort of distraction if it is not well considered in design [29
]. More specifically, only a single modality should require the conscious discovery of new affordances from the user, or require much and continuous cognitive effort to be operated. Yet the choice of these modalities might well depend on the specific focus or narrative of the intended communication. For instance, when intending that museum visitors should focus on the Nile, a touch display might be more suited.
5.2. Role of Physical Representation
The level of realism, the physical construction and the manipulation features of a 3D scale model influences how people observe and remember architectural qualities, particularly when compared to a 2.5D interactive walk-through rendering. In the condition of physical representation (i.e., Tang-Phys
), most participants understood intuitively the symbolic significance between the colonnade and the map. We believe that Tang-Phys
enabled the communication of the symbolic significance because of the direct link between the movement of the statue along the Nile and the corresponding lights in the physical colonnade, that was easy to perceive as “the parallelism of the colonnade and the map was too easy … with lights, it is evident”
(participant 38). As the digital representation conditions (Touch-Dix
) reached a relatively lower percentage of participants who readily understood this symbolic significance (as shown in Table 2
), understanding the link between the navigation and representation was more ambiguous and more challenging, probably because “it was contradictory to move the control (statue) through the river, and at the same time to see the building”
(participant 6) from Tang-Dix
condition. On the other hand, we observed several unexpected results in Tang-Phys
condition, particularly regarding how participants perceived or remembered certain architectural qualities. For instance, participants perceived the spatial proportions differently. The average estimated width of the colonnade in Tang-Phys
condition was more or less the correct external width including the width of the outer walls, whereas the length was somehow overestimated. The shape of the columns were perceived by 6 participants (N = 15) as non-circular. The colors and materials were less well perceived when using the physical model in comparison to the other conditions, “I cannot understand the materials form this model … ancient Egyptian buildings did not have marble, so it is limestone”
(participant 27). We hypothesize these observations were mainly due to the particular physical properties of the scaled model of the colonnade. To allow for visual investigation from the top, the model lacked a ceiling, which in turn caused people to observe the length from above. In addition, the columns were ‘cut through’ at their very top end, which are square. Finally, people perceived the ‘external’ width including the thickness of the walls, whereas the walk-through view only allowed a view from inside.
We propose that future comparative experiments should have quasi-identical levels of representation abstraction in both the digital renderings as the physical models, and that spatial estimation questions could potentially be fine-tuned by asking participants to also draw the thickness of the walls and ceilings (Figure 10
b). Yet we also wish to point out how seemingly trivial issues like opening ceilings or vertically sectioning a building can easily become misconstrued by visitors. As a result, an equilibrium needs to be found between the positive qualities of tangible interaction via physical representations and the actual level of realism that can be fabricated within obvious constraints of financial costs, robustness and historical accuracy. While often absolute realism is wished for, abstraction and ambiguity is a well-known design method to engage users to take responsibility in interpreting its meaning and functionality [45
5.3. Role of Grasping
We believe that grasping a physical model, bringing it closer to one’s eye and observing it from different angles facilitates the communication of correct scale and more detailed information. In the graspable-centered sub-condition of Tang-Phys, all participants understood the symbolic significance of the story, led to more precise communication of the architectural scale (i.e., width of the colonnade and proportion), and to more accurate estimations of the number of fluted columns and their shapes in the graspable sub-condition, particularly compared to the identical sub-condition during which participants could not grasp the physical model itself (i.e., fixed).
This evidence encourages further developments in allowing visitors to grasp physical models or replicas for better communication of the tacit knowledge or the finer details of heritage artifacts. However, to enable tangible forms of interaction, graspable models must be equipped with sensors (e.g., touch, orientation) or actuators (e.g., lights, motors) that are subtly embedded almost or wirelessly connected. In addition, such technological interventions should be meaningful, respectful and intuitive to be understood [46
]. In addition, the technology itself could potentially disturb an immersive experience of the heritage communication. For instance, during our study, some participants were curious to discover the hidden technology driving the installation in the graspable
sub-condition, probably because of the visible wiring. Furthermore, interactive objects require affordable and robust forms of technology, which cannot be simply stolen or damaged, and thus issues of cost and ease of replacement should be well considered [26
5.4. Role of Material Characteristics
The intrinsic multimodal characteristics of tangible interaction requires taking into account characteristics that reach well beyond the graphical, including aspects such as embodiment, physical abstraction, and materiality (i.e., texture, weight, friction, etc.)
We believe a persuasive part of tangible interaction is its ability to offer participants the opportunity to decipher its affordances through different forms of embodiment, in order to allow them to discover the interactive features as well their potential meaning in forming a historically valid narrative. To entice a sufficient level of curiousness and engagement, this discovery process should be non-obvious yet sufficiently simple that people feel encouraged to explore all the hidden functionalities without frustration. Within our design, we therefore exploited the concept of embodiment, which is considered one of the main attributes of TUIs because it supports learning unconsciously [47
]. According to [48
], embodiment plays a constitutive role in communicating heritage information when it is entangled through context and environment, which enables visitors to get more involved in historical stories [49
]. We considered several forms of embodiment when designing the Tang-Phys
condition. For instance, we made a physical representation of the Djoser pharaoh which was able to be moved along a groove representing the Nile River (Figure 10
a), embodying his journey along the Nile. The physical representation model showed the space from above, embodying the architectural qualities of flutedness by 3D printing them (Figure 10
b). Overall, the small physical model embodied the spatial experience of the colonnade when the model was grasped and viewed on eye-level, so that the columns and small statues appeared as they were ‘in the space’ (Figure 10
Likewise, we propose that the concept of physical abstraction plays a crucial role in the imagined potential of more embodied forms of representation, as a crucial difference exists between the abstracted neutral aesthetic of a model fabricated out of white, thick walls in condition Tang-Phys versus the more realistically colored stone brick textures on the digital 2.5D models in the other two conditions. Consequently, participants tended to differ in opinion in terms of the ideal level of abstraction, as some Tang-Phys participants complained about too much abstraction in the physical model, “I have a difficulty in imagination … I have to see something in 3D to form a real image about it” (participant 25), whereas others (from Touch-Dix) actually wanted a more abstract form of visualization for the digital renderings: “you can gain a better sense of information if you look at the colonnade from a top view” (participant 41). For some participants, the geometric and 3D-aesthetic of the 2.5D rendering made it look like a ‘game’: “it did not look very well … the quality looked a bit (like a) video game” (participant 7, Tang-Dix).
Tangible interaction requires the material construction of objects, making the concept of materiality relevant for both the navigation (input) and the representation (output) modalities, as the power of material characteristics enable heritage visitors to acquire the cultural meanings [29
]. According to [50
], materiality emphasizes the visitor’s sensations and personal interpretations of heritage information through the physical objects they interact with. For instance, the texture (i.e., rough versus glossy surface) of the physical model probably impacted how people imagined the spatial qualities of the colonnade, and the materials they imagined the colonnade to be of marble “a rough colonnade, maybe made out of marble”
(participant 26). The experienced weight and friction of moving the pharaoh along the groove also played a role in the general experience of the installation “I like it because I can move the pharaoh along the Nile”
(participant 38), and “with the colors, I prefer this part [navigation] because I interact and touch the statue”
(participant 36) from Tang-Phys
Overall, one could argue an equilibrium needs to be sought towards the average preferences of the public at large in terms of deciding the embodiment, abstraction or materiality. As when too much emphasis is put on the information, the physical object dissolves into meanings [51
]. Yet, the mentioned concepts are also potentially powerful design aspects that could become exploited for more explicit design goals in steering useful forms of tangible interaction. For instance, the actual embodiment of narratives and historical facts could be made more ambiguous to allow visitors to guess their metaphorical meaning, whereas a varying level of abstraction could relate to the corresponding level of historical accuracy of current heritage knowledge. Likewise, heavy or glossy objects could guide the attention of visitors towards more precious or historically valuable aspects of a specific site or objects.
5.5. Shortcomings and Limitations
In our study, the experiments were deployed for a relatively short time with a limited number of participants. Due to the corresponding small sample size, the results of the UEQ did not show any significant statistical differences among the conditions. We also realize that the conclusions might be limited to conveying information by ways of tangible interaction that links direct navigational input controlled by users unto locative information that has a metaphorical meaning. At the same time, we believe that most of our findings can be generalized towards many other forms of tangible interactions that are meant to communicate information towards a lay audience.
We used only low-fidelity prototypes in our experimental conditions, which is known to lower the expectations of participants [52
]. This observation also was demonstrated by how many participants expected ‘more’, particularly in terms of the information that was offered: “you see only this corridor, but if it is linked to information of these [the nomes], that could be very interesting”
(participant 21) from Touch-Dix
; as well as in terms of interactive features: “it would be better if during the interaction, the person in the 3D model gives us some explanations”
(participant 40) from Tang-Dix
. With regard to the experiment setup, the informative poster was displayed in Tang-Phys
condition on the large LCD display behind the installation instead of hanging it on the wall in the other two conditions (Figure 2
d–f). This setup might affect the results because the display was larger and placed in a more prominent location, although the chronological analysis (Figure 7
) does not show more focus on the poster in this condition, but this could be due to the manual observation and analysis. Additionally, due to language barriers, only few families involved their children in answering the questions during the interview and all the internal discussions among families were in their own language. Accordingly, it was challenging to report on the age-related differences in terms of how children understood the symbolic significance and how they comprehended the spatial aspects. Moreover, on busy museum days with large crowds, our installation might not be ideal, as queues could form. It could be ameliorated by choosing a social approach, one that allows people to share their experience with each other. For instance, multiple scale models could be used and light up. Furthermore, according to the concept of participatory museum and connecting visitors [53
], we believe that incorporating a TUI in our prototype might well increase the interactions among museum visitors who do not know each other to actively engage and to socially interact, not only among families [54
]. However, due to the limited number of participants and the short time of the experiment, we only observed and mapped the discussion and social interaction among the visitors who knew each other in advance and arrived in groups (i.e., family visits or group of friends). Accordingly, we recommend that the influence of these kinds of installations on social interaction in a museum context should be further investigated.