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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>What if Interactive Explanation in a Scientific Literature Recom mender System</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Mouadh Guesmi</string-name>
          <email>mouadh.guesmi@stud.uni.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Mohamed Amine Chatti</string-name>
          <email>mohamed.chatti@uni-due.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Jaleh Ghorbani-Bavani</string-name>
          <email>jaleh.ghorbani-bavani@stud.uni-due.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Shoeb Joarder</string-name>
          <email>shoeb.joarder@uni-due.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Qurat Ul Ain</string-name>
          <email>qurat.ain@stud.uni-due.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Rawaa Alatrash</string-name>
          <email>rawaa.alatrash@stud.uni-due.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Social Computing Group, Faculty of Engineering, University of Duisburg-Essen</institution>
          ,
          <addr-line>47048 Duisburg</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Despite the vast amount of research on interactive recommender systems (RS) and explainable recommendation, there is a lack of research on how to incorporate interactivity features in explainable RS. To address this research gap, a possible solution to achieve interactive explanation could be to provide What if explanations that can help users iteratively build better mental models of how the RS works. Through an iterative human-centered design (HCD) process, we designed What if interactive explanations in the transparent Recommendation and Interest Modeling Application (RIMA) and explored how this type of explanation could impact the understandability of and interaction with an explainable RS. Our investigation showed that providing What if explanations has a positive efect on diferent aspects of a RS such as transparency, trust, user control, satisfaction, and user experience.</p>
      </abstract>
      <kwd-group>
        <kwd>Recommender system</kwd>
        <kwd>Explainable recommendation</kwd>
        <kwd>Interactive explanation</kwd>
        <kwd>What if explanation</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>Similar to most artificial intelligence (AI) applications, recommender systems (RS) often act
as black boxes for the end-users. To alleviate this problem, explainable recommendation has
attracted much attention in the RS research community. Explanations are a necessary condition
to help users build an accurate mental model of the RS [1, 2, 3]. Generally, explanations seek to
show how a recommended item relates to a user’s preferences [4]. Explanation is inherently a
social process [5, 6]. The social nature of explanation implies that an explainable RS has to be
interactive. Over the past years, a growing body of research has focused on visual interaction
and control mechanisms for RS [7, 8]. It has been shown that interactive recommendation and
user control can improve user experience and trust in the RS [9, 10, 11]. Several researchers,
however, identified that there is a lack of research on interactive explanation in RS [ 12, 13, 14, 15].
While many recognize the necessity to providing user control and interaction mechanisms in
the context of explanations, how to design, implement, and evaluate interactive explanation in
RS remains an open question.</p>
      <p>To address this research gap, in this paper, we focus and elaborate on the concept of What
if explanation as a viable path to interactive explanation. Our aim is to follow a
human-inthe-loop approach where users can steer the explanation process to build an accurate mental
model of the RS. Taking scientific literature RS as our domain, we systematically designed
What if explanations in the transparent Recommendation and Interest Modeling Application
(RIMA). When interacting with RIMA, users can ask exploratory What if questions to keep
closing the gap of understanding and scrutinize the RS (i.e., correct the system’s assumptions)
if necessary. Further, we conducted moderated think-aloud sessions and semi-structured
interviews with students and researchers (N=12) to systematically study how users perceive
What if interactive explanations in an explainable RS. The results of our study show that
providing What-if explanations has a positive efect on diferent aspects of a RS such as
transparency, trust, user control, satisfaction, and user experience.</p>
      <p>The main contribution of this paper is twofold: first, we follow a human-centered design
(HCD) approach to efectively design What if interactive explanations aiming at clarifying the
background behavior of the RS by allowing users to adjust the set of inputs and monitor the
possible results. Second, we provide evidence on the positive impact of What if explanation on
the perception of explainable recommendation.</p>
      <p>This paper is organized as follows. We first outline the background for this research and
discuss related work. We then present the systematic design of the What if explanations in
RIMA. Afterwards, we describe the user study and present its results. Finally, we summarize
the work and outline future research plans.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work</title>
      <sec id="sec-2-1">
        <title>2.1. Interactive Explanation</title>
        <p>In a broader view, an explanation aims to make the reasons behind a decision or recommendation
comprehensible to humans. Thus, work on XAI in general and explainable RS in particular must
take a human-centered approach. To this end, the HCI community has called for interdisciplinary
collaboration and user-centered approaches to XAI [16, 17]. For instance, Wang et al. [17]
proposed a conceptual framework to connect XAI techniques and cognitive patterns in
humandecision making to guide the design of user-centric XAI systems. Liao et al. [18] provided an
XAI question bank and discussed how it can be used for creating user-centered XAI. Miller [5]
synthesized perspectives on human explanation from philosophy, social science, and cognitive
science and identified a list of human-friendly characteristics of explanation, including that
human explanations are contrastive (i.e., “sought in response to particular counterfactual
cases”), selective (i.e., selected in a ‘‘biased manner” from a “sometimes infinite number of
causes”), and social (i.e., conversational process, where an ”explainer transfer knowledge to
an explainee”). Similarly, Hilton [6] stressed that explanation is inherently a social process. It
involves the interaction between explainer and explainee engaging in information exchange
through dialogue, visual representation, and other communication modalities. The social nature
of explanation implies that an XAI has to be interactive or even conversational [18]. With
the goal of bridging the gap between XAI and HCI, research on designing and studying user
interactions with XAI has emerged over the past few years [19, 20, 21, 22]. However, little is
known about how interactive explanation should be designed and implemented in RS, so that
explanation goals such as scrutability, transparency, trust, and user satisfaction are met [12, 13].</p>
        <p>Although interactive and more recently conversational RS have been well studied [7, 23, 8,
24, 25], there has been little work on how to incorporate interactivity features in explainable RS.
Both in the literature and in real-world systems, there are only a few examples of RS that provide
interactive explanations, mainly to allow users to scrutinize the provided recommendations
and correct the system’s assumptions [12, 26, 27, 28, 29, 30], or have a conversation, i.e., an
exchange of questions and answers between the user and the system, using GUI-navigation or
natural language conversation [13].</p>
        <p>A distinction is to be made here between interactive recommendation and interactive
explanation. While both empower users to take control of the RS process, they difer in the goal
of the control action. While the primary goal of interactive recommendation is to improve
and personalize the recommendation results, the goal of interactive explanation is to help both
the users for better understanding and the system designers for better model debugging. In
this paper, we focus on What if explanation as a possible mechanism to achieve interactive
explanation in RS.</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. What if Explanation</title>
        <p>An explanation can be seen as an answer to questions, also called intelligibility queries or types,
such as What, Why, How, Why not, How to, and What if [31, 5, 18, 32]. Relevant to our work are
What if explanations. These explanations allow users to speculate what the application would
do given a set of user-set input values [33]. In XAI, they show how the prediction changes
corresponding to changes of a feature (often in a visualization format) [ 18]. What if explanation
difers from counterfactual ( How to) explanation in that while the former asks about prospective
future behavior (i.e., what if the factors were diferent, then what the efect would be?), the
latter asks retrospectively (i.e., what needs to change for the alternative outcome to happen?)
[34]. In an RS context, What if explanations deal with the manipulation of inputs to the RS.
These explanations illustrate how the manipulation of inputs afects the output of the RS, i.e.,
recommendations. These explanations involve users’ interaction with the system when they
can change an input to the RS and want to know what will happen as a consequence. What if
explanations aim to answer the question: ”What if there is a change in my profile, what would
happen?” [35].</p>
        <p>The majority of previous research on What if scenarios in RS has focused on What if
interactions with the RS, rather than with the explanation components of the RS. For example,
Schafer et al. [14] studied the efects of what they called hypothetical recommendations (i.e.,
recommendations generated by What if exploratory profile manipulations). In particular,
the authors evaluated the efects of dynamic feedback from the RS on profile manipulations,
the resulting recommendations, and the user’s overall experience. Zürn et al. [36] discussed
possible UI extensions to explicitly support What if interactions with RS, which allow users to
explore, investigate and question algorithmic decision-making. Our work difers from previous
approaches in that we focus on What if interactions with the explanation components of the
RS and that we attempt to determine the impact of What if explanation on the perception of
explainable recommendation.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. What if Explanation for scientific literature recommendation</title>
      <sec id="sec-3-1">
        <title>3.1. RIMA Application</title>
        <p>We developed the transparent Recommendation and Interest Modeling Application (RIMA) with
the goal of providing explainable interest models and recommendations. RIMA is a
contentbased RS that produces content-based explanations. It follows a user-driven personalized
explanation approach by providing explanations with diferent levels of detail and empowering
users to steer the explanation process the way they see fit [ 28, 26]. The application provides
on-demand explanations, that is, the users can decide whether or not to see the explanation [15].
In this work, we focus on recommending scientific publications and leveraging explanatory
visualizations to provide What if interactive explanations aiming at clarifying the background
behavior of the RS by allowing users to adjust the set of inputs and monitor the possible results.</p>
        <p>The user interest models in RIMA are automatically inferred from users’ publications [37].
Based on these inferred interest models, the recommendation engine provides scientific
publication recommendations. The top five interests (based on their weights) are initially used as input
for the recommendation process. For obtaining the candidate publications, we use the semantic
scholar API to fetch publications that contain, or are related to, one or more user interests that
are used as input for the recommendation. We then apply an unsupervised keyphrase extraction
algorithm on the fetched publications to extract keywords from the title and the abstract text.
In order to compare the similarity between the user interests and the candidate publications,
we use word embedding techniques to generate vector representations of the user interest
model and the recommended publications. After getting the two embedding representations
(i.e., interest model embedding and publication embedding), we calculate the cosine similarity
between them in order to obtain a semantic similarity score. The top ten similar publications
will be then recommended to the user. Initially, publications with a semantic similarity score
above a threshold of 40% will be displayed to the user.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. What if Explanation Design</title>
        <p>An elegant translation of machine-generated explanations needs carefully designed
humanunderstandable and satisfying explanations in the user interface [32]. The What if explanation
presents an exploratory profile manipulation (i.e., addition, deletion, or re-weighting interests).
Similar to counterfactual or contrastive explanations, What if explanations not only pinpoint
the causes of a model decision but also provide users with actionable levers to change the
recommendation [38]. According to Lim [39], the What if explanations would have to be interactive
and dynamic, as they depend on example scenarios that users define themselves. Moreover, the
results from Szymanski et al. [40] revealed that most users prefer visual explanations. Therefore,
we aim at providing What if explanation using interactive visualizations.</p>
        <p>The explanation scope or interpretation scale is another important dimension to be considered
when designing explanations, which could be either local or global [32, 38]. Global explanation
(or model explanation) is an explanation type that describes how the overall machine learning
model works, while local explanations (or instance explanation) aim to explain the relationship
between specific input-output pairs or the reasoning behind the results for an individual user
query [32]. Moreover, local explanation is thought to be less overwhelming for novices, and it
can be suited for investigating edge cases for the model or debugging data [32]. Inspired by this
distinction in terms of explanation scope, in this work, we aim at providing local and global
What if explanations.</p>
        <p>Building upon the insights from the literature outlined above, we followed the
HumanCentered Design (HCD) approach [41] to systematically design interactive visualizations of the
What if explanation. Designing with the HCD approach ensures that the needs and requirements
of the user are taken into consideration as it is based on involving users from the very beginning
and regularly consulting them for the evaluations of incremental prototypes. The HCD process
consists of four consecutive activities, namely Observation, Ideation, Prototyping, and Testing.
These four activities are iterated; that is, they are repeated over and over, with each cycle
yielding more insights and getting closer to the desired solution [41]. The final design of these
What if interactive explanations was the result of three HCD iterations. For evaluating the
diferent explanation prototypes, a group of potential users was selected to participate in the
design process. Our target group was researchers and students who are interested in scientific
literature. For each design iteration, five diferent potential users were involved to test and give
feedback on the provided prototypes, as recommended by Nielsen [42] in the case of qualitative
user studies.</p>
        <sec id="sec-3-2-1">
          <title>3.2.1. First iteration</title>
          <p>Through this initial step, we aim at understanding users’ needs and initiating the first low-fidelity
prototypes for the What if explanation.</p>
          <p>
            Observation. We conducted interviews with five potential users in order to gather the user’s
requirements in an explainable scientific literature RS. Through the interview, we investigated
users’ expectations from a What if explanation, as well as the expected level of interactivity and
controllability over this explanation. Based on the interviews, we gained a better understanding
of the end-user expectations and needs. The interviewed users agreed on four main scenarios
for using What if explanations: (
            <xref ref-type="bibr" rid="ref1">1</xref>
            ) when they are not satisfied with the whole RS results, (
            <xref ref-type="bibr" rid="ref2">2</xref>
            )
when the recommended publications are not expected, (
            <xref ref-type="bibr" rid="ref3">3</xref>
            ) they want to interact with the RS to
discover more recommendations, and (4) they are not satisfied with a specific recommended
publication and interested to know why it was recommended.
          </p>
          <p>Ideation. The ideation phase was focused on generating ideas about how to provide
interactive What if explanations that address the four scenarios from the observation phase.
A brainstorming session involving four authors and seven students from the local university
having knowledge in RS and information visualization was carried out to collect as many ideas
as possible for each scenario where we put quantity of ideas over quality. For each scenario,
every idea was written down then discussed following a “pitch and critique” approach to gather
both positive and negative feedback for each idea. The last step was the voting process to select
the best ideas. In the end, we selected and categorized the top three voted ideas for each What
if explanation scenario.</p>
          <p>The ideation phase resulted in a global and a local What if explanation design. The global
What if explanation aims at helping users interact with the explanation to answer the following
questions: ”What if I change the weights of my interests? ” or ”What if I change (add or delete)
my interests?” in order to deal with the first three scenarios, namely when users are not satisfied
with or did not expect the RS results, or when they want to discover new recommendations. The
local What if explanation addresses the fourth scenario when users might not be satisfied with a
specific recommended publication and interested to know why it was recommended. In this case,
users can interact with their interest profiles as well as with the set of keywords extracted from
the publication for two reasons; either they want to understand the reason behind providing
that specific publication as a recommendation through the provided similarity computations,
or they are curious to know what would happen if their interests (or their weights) or the
publication keywords changed. The local What if explanation can thus be used to question
the recommendation of a specific publication by manipulating the interest model or the set of
the extracted keywords from that publication. This explanation could answer the following
questions: ”What if I change my interests (add, delete, modify the weight)?” or ”What if I change
the keywords extracted from the publication (add or delete keywords)?”.</p>
          <p>Prototyping. The next step was to come up with possible visualizations for the global and
local What if explanations. For each explanation scope, we discussed various visualizations and
created low-fidelity prototypes as paper mock-ups. The goal of the global What if explanation
is to provide users with an overview of the recommended publications, as well as reveal the
relationship between these publications and the user’s interests. We proposed three visualizations
to show these relationships, namely bar chart, polar area chart, and stacked bar chart. Users
can interact with the visualization by selecting publications for more details, or by changing the
weight of an interest using a slider. The goal of the local What if explanation is to make users
understand the relationship between their interests and a specific recommended publication.
This explanation should allow users to manipulate (a) the interest model either by adding or
deleting interests or changing the weight of specific interests or (b) the set of automatically
extracted keywords from the publication by removing or adding new ones. We chose bar chart
and polar area chart to visualize the impact of the interests’ weights on the recommendation
output, and heatmap to depict the similarity between all interests and all extracted keywords.
Similar to the global What if explanation, users can interact with the visualization through
selecting and changing actions.</p>
          <p>Testing. The evaluation of the initial low-fidelity prototypes aims to receive feedback for
optimization. This feedback was collected through a qualitative evaluation with five
potential users following a think-aloud approach where we used open-ended questions to ask the
users about their thoughts on each of the selected visualizations and their opinion towards
the proposed What if explanations. The purpose is to understand to what extent each of
the visualizations was able to convey the intended purposes of the global and local What if
explanations to the user. Regarding the global What if explanation, users agreed that bar chart
is the most suitable chart to present the similarity between their interests and the recommended
publications. However, they mentioned that the new recommended publications obtained after
interacting with the What if explanation are not specified or highlighted in the visualization.
Also, they suggested avoiding polar area and stacked bar charts with the argument that if they
have a considerable number of interests, the visualizations will be overwhelming and confusing
to a certain degree. Similarly, they selected bar chart for the local What if explanation as polar
chart, area chart, and heatmap should be avoided for the same previous reasons. Furthermore,
they reported that they liked the feature of monitoring in real-time whether the publication will
still be recommended or not after making the changes. Accordingly, the selected visualizations
for both global and local What if explanations were bar charts, as shown in Figure 1.</p>
        </sec>
        <sec id="sec-3-2-2">
          <title>3.2.2. Second iteration</title>
          <p>This step aims to overcome the deficiencies of the previous designs by considering users’
feedback collected from the previous testing phase. The prototypes in the second phase are
designed using the Figma tool, but still considered as low-fidelity prototypes.</p>
          <p>Prototyping. For the global What if explanation, the decided visualization was a bar
chart that shows similarity scores between the user interest model and all the recommended
publications (Figure 2). The control panel at the top of the visualization allows the user to
change the weights of their interests. In addition, this visualization gives the user an overview
of potential results (i.e., hypothetical recommendations) as a response to a user’s change and
asks for their decision to keep or cancel the changes (Figure 2a). In order to overcome the issue
of specifying and highlighting the newly added publications, we used colors to indicate the
publications’ status and distinguish between the old recommendations (i.e., before interacting
with the what if explanation), the omitted recommendations (i.e., those removed after interacting
with the What if explanation), and the new recommended publications (i.e., those added after
interacting with the What if explanation) (Figure 2b).</p>
          <p>The aim of the local What if explanation is to explain to the user the factors influencing
the recommendation process of a specific publication. This explanation should allow users
to manipulate their interest models or the set of automatically extracted keywords from the
publication and see the consequences of these actions. To achieve this, we used two bar
chart visualizations, as suggested by users in the first iteration. In the first bar chart, each
bar shows how similar are the individual interests to a specific publication (Figure 3a). The
ifxed gray bars in the background represent the initial similarity scores before interacting
(i.e., adding/removing an interest or changing its weight) with the explanation. The displayed
score on the bars represents the similarity score between a specific interest and the selected
publication. In addition to manipulating their interest profiles, the users can also remove the
extracted keywords from the publication or select new ones to be taken into consideration.</p>
          <p>The second bar chart is used to show the similarities between the user-selected publication’s
keywords and the user interest model (Figures 3b and 3c).</p>
          <p>(a)
(b)
(c)</p>
          <p>Testing. The second evaluation round was conducted with five other users. Related to the
global What if explanation, users were satisfied with the provided bar chart visualization as an
explanation and they reported that it helped them understand the reason behind getting such
recommendation. Moreover, they liked that they can get real-time changes when they want
to test diferent scenarios by manipulating their interests. Further, they mentioned that using
colors to distinguish between the recommended publications’ status was helpful for them to
immediately see the impact of the changes they performed on their interest model. However,
they suggested making the bars clickable in the visualization to allow them to see more details
about a specific publication. That means users sometimes want to get a local explanation from
the global explanation interface.</p>
          <p>As far as the local What if explanation is concerned, users mentioned that besides the
similarity score between each interest and the recommended publication, they want to see the
similarity score between their whole interest model and the selected publication. Also, they
reported that they liked the background gray bars as they represent the initial similarity score
before they make changes, so they can easily compare the results. However, one of the main
critiques for this visualization was the lack of the final decision if the current publication will
still be recommended or not after changing their interest models. Overall, the evaluation of
the second iteration prototypes revealed that the users had mostly similar positive opinions
regarding the proposed bar chart visualizations and the expected interactions with the global
and local What if explanations.
3.2.3. Third iteration</p>
          <p>Based on the previous iterations and following the feedback from users, we designed and
implemented the final prototypes of the global and local What if explanations in the RIMA
application (Figure 4). The main user interface consists of the list of the top five user’s interests
(Figure 4a), as automatically generated by the system. In order to easily identify the interests
and their impact on the recommendation, we used unique color for each interest. This user
interface displays the list of the recommended publications in form of separated boxes (Figure
4b), containing a relevance score for each publication (Figure 4c). We provide a color band next
to each publication. The colors are the same ones used for the user interests on the top. The
height of each color bar indicates how relevant is this publication to the related interest (Figure
4d). Users can access the global What if explanation through a ”WHAT-IF?” button provided
on the upper box where they can see their interests (Figure 4e). The local What if explanation
is provided through another ”WHAT-IF?” button on the bottom-right side of the box for each
recommended publication (Figure 4f).</p>
          <p>For the global What if explanation (Figure 5), we provided a bar chart visualization that shows
the similarity scores between the recommended publications and the interest model (Figure 5a).
A slider on top of the bar chart visualization allows users to control the similarity threshold
used by the RS. Only publications above the user-specified threshold value will be displayed.
We implemented the color feature regarding the indication of the publication’s status (old: blue,
new: green, or omitted: red) (Figure 5b). As requested by users in the previous iteration, we
made the bars clickable so they can see a more detailed explanation for each publication. This
visualization shows similarity scores of the selected publication to each interest after a user
clicks on a specific publication in the initial bar chart (Figure 5c).</p>
          <p>Regarding the local What if explanation, we provided two visualizations for the user. The first
visualization allows users to understand the reason behind getting a specific recommendation
by manipulating their interest models. As requested by users in the previous iteration, we
provided another bar chart next to the initial visualization to show the similarity score between
the whole interest model and that specific publication, which is changed in real-time based
on the user’s actions (Figure 6). The second visualization enables users to change the list of
keywords that were automatically generated by the RS, and see how this afects the computed
similarities between the user-selected publication’s keywords and the user interest model, and
whether in that case the publication will be recommended or not (Figure 7).
Figure 7: What if local explanation – similarities between publication’s keywords and interest model:
(a) before interaction (b) after interaction.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Evaluation</title>
      <sec id="sec-4-1">
        <title>4.1. Study Design</title>
        <p>After systematically designing the What if explanations and implementing them in the RIMA
application, we conducted a quantitative and qualitative user study to explore the usage and
attitudes towards our scientific literature RS, considering the What if explanations. Researchers
and students interested in scientific literature were invited to participate. 12 participants took
part in this study. Participants were between 20 and 39 years old, where half of them were
master’s graduates or higher, and the other half were master’s students. All participants gave
informed consent to study participation.</p>
        <p>
          Participants were initially given a short introductory video about the RIMA application in
general, and another short demo video about the What if explanation feature in the application.
Next, they answered a questionnaire in SoSci Survey which included questions about their
demographics and familiarity with RS and visualization. Afterwards, we conducted moderated
think-aloud sessions where participants were asked to (
          <xref ref-type="bibr" rid="ref1">1</xref>
          ) create an account using their Semantic
Scholar ID (users who do not have Semantic Scholar IDs can generate their interest models
manually) in order to create their interest models, (
          <xref ref-type="bibr" rid="ref2">2</xref>
          ) interact with the application based on
given scenarios, and (
          <xref ref-type="bibr" rid="ref3">3</xref>
          ) take a closer look at the What if explanations provided by the system.
Following a think-aloud approach, the participants were also asked to say anything that comes
to their mind during each interaction. After that, we conducted semi-structured interviews to
gather in-depth feedback. The interviews took place online and were recorded with the consent
of the participants. They lasted 10 to 15 minutes with the following questions: (
          <xref ref-type="bibr" rid="ref1">1</xref>
          ) What do
you like the most about the provided What if explanations? (
          <xref ref-type="bibr" rid="ref2">2</xref>
          ) What do you like the least about
the provided What if explanations? (
          <xref ref-type="bibr" rid="ref3">3</xref>
          ) Why / When (in which situation) / How often would you
like to use each of the provided explanations? (4) How much has the controllability of the What
if explanations influenced your satisfaction with the recommended publications? Do you have
any suggestions to improve the controllability of the What if explanations? (5) Which What if
explanation gives you a better sense of transparency of the recommender system? Why? (6) Which
What if explanation gives you a better sense of trust in the recommender system? Why? (7) Do you
have any suggestions to improve the system?
        </p>
        <p>After the semi-structured interviews, participants were also invited to fill out a questionnaire
containing questions regarding usability aspects and attitudes towards the RS, based on the
ResQue evaluation framework [43].</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Analysis and Results</title>
        <p>The results of the ResQue questionnaires are summarized in Figure 8. Besides our quantitative
analysis, we also conducted a qualitative analysis of the moderated think-aloud sessions and
the semi-structured interviews to gain further insights into the reasons behind the individual
diferences in the perception of the RS in terms of the What if explanations. We followed the
instruction proposed by Braun and Clarke [44] to code the data and identify patterns to organize
the codes into meaningful groups. Notes and transcripts of the interview recordings were made
for the analysis. The analysis was rather deductive as we aimed to find additional explanations
for the findings of our quantitative analysis. We present the results of the evaluation organized
by four themes, which were adapted from the ResQue framework, namely Transparency and
Trust, User Control, Satisfaction, and Overall User Experience.</p>
        <sec id="sec-4-2-1">
          <title>4.2.1. Transparency and trust</title>
          <p>This theme concerns the perception of the What if explanations and visualizations in terms of
transparency and trust. In this regard, participants stated that the visualizations had a good
efect on transparency in the system and they pointed to the possibility of making changes
and observing the efect on the results. For instance, P6 mentioned that ”Through what if
explanations, I could see how the results will change”. However, some of them could not identify
some aspects of the system behavior clearly. When we asked the participants in the think-aloud
session to explain how the system works and name the factors influencing the recommendation
process, all of them could successfully mention that interests and weights play the main role
in the recommendation process. They also stated that the similarity between their interests
and the publication is the criteria to select which publication to recommend. However, three
participants pointed out that the role of keywords was not clear to them.</p>
          <p>Although six participants did not speak very confidently about trust in the system, they
described that the consideration of interests in selecting publications to recommend, showing
the similarity score between interests and publications, and how they are displayed with colors
and numbers had caused more trust in the RS. However, on the other hand, they mentioned
that there are uncertainties in extracting keywords from the publications and calculating the
similarities in the What if explanations, which justified negative opinions about the system
trustworthiness: ”P8: It’s dificult to say, some words are not extracted but they are close to one of
my interests and this can make me disappointed”. ”P2: It comes to my mind that there are some
relevant publications that maybe the system is not recommending and I might have lost them”.</p>
        </sec>
        <sec id="sec-4-2-2">
          <title>4.2.2. User control</title>
          <p>Most of the participants indicated a favorable opinion towards the control of the
recommendations (see Figure 8): ”P1: When I change my interests or the keywords in a way that I wanted
it has a good influence on the item which will be recommended and I like that it’s exactly based
on my interest”. Their answers to the questions in the semi-structured interview about the
controllability of the recommendations also indicate their satisfaction with the system. Also,
we found that the provided controllability over the system and the explanations is suficient
and users were satisfied with it as they declared that it was enough and they didn’t suggest
any improvements: ”P3: I think the controllability is enough because there is nothing out of my
control.”</p>
        </sec>
        <sec id="sec-4-2-3">
          <title>4.2.3. Satisfaction</title>
          <p>Most of the participants were satisfied with the provided What if explanations in the RS (see
Figure 8). Participants indicated that they tend to use the What if explanations when the results
were not favorable to them and that the global What if explanation to adjust their interests in
order to get more accurate recommendations is the most appropriate explanation in this case.
Regarding the local What if explanation, the participants mentioned that they tend to use it
when they feel dissatisfaction with the recommendation in a particular case and that either
the similarity calculations or keywords extracted from the publication might not be incorrect,
so they have the ability to correct the system and improve the recommendation quality: ”P1:
When I find unexpected and irrelevant items I would like to use the local What if explanations” .
Moreover, they mentioned that the local What if explanation helps them discover which one of
their interests is most similar to the publication. However, most of the participants stated that
they would use the global What if explanation more often than the local one.</p>
        </sec>
        <sec id="sec-4-2-4">
          <title>4.2.4. Overall user experience</title>
          <p>For this theme, we gathered feedback concerning the situations where each explanation is used.
Controlling interests, real-time visual explanations of the made changes, and changing the
publication keywords were the features that participants liked most in the What if explanations.
Overall, the users liked that whenever the recommended items are not aligned with their
expectations, they can easily interact with the system through the What if explanation interface
to report errors and understand why a publication is recommended. All the answers indicated
that changing the input and observing its efect on the results, especially in the global What
if explanation, was a favorite feature for all participants: ”P10: I liked that I could change the
keywords and interests when the recommended items were not desired”. On the other hand, two
participants did not like the similarity threshold and stated that it was unnecessary for them.
Also, three participants found that the visualization is complicated and reported that ”P3: It
may take some time to figure out what information the charts is providing” .</p>
          <p>When participants were asked about how to improve the system, most of the answers were
about improving the application user interface. For example, P3 mentioned that she didn’t
like the amount of color used in the application. According to the participants’ opinions about
the user interface, it can be concluded that the interface should be improved from a usability
perspective.</p>
          <p>While interacting with the system, we observed and examined user actions. The result
was that a few users were challenged to find the What if keywords explanation, and in other
cases, they could handle the defined situations well. In addition, they quickly realized the
functionality of control panels, visual explanations, and how to interact with visualizations.
Participants perceived the system as easy to use and showed an overall positive attitude towards
the user experience. We could observe that they were able to use the explanations in the
right situation and with a true reason. In addition, participants showed a high perception of
the system’s usefulness as they pointed out several times that they were able to find relevant
publications by controlling their interests and weights. They also said that by limiting the
domain of search, which is applicable by changing the interests and weights, one can get close
to the right recommendation.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Conclusion and Future Work</title>
      <p>Explanations are important to help users build an accurate mental model of how a recommender
system (RS) works. Despite the wide agreement on the benefits of interaction and user control
in RS, explanations in RS have so far been presented mostly in a static and non-interactive
manner. To address this research gap, in this paper, we focused and elaborated on the concept
of What if explanation as an efective mechanism to achieve interactive explanation in a
scientific literature RS. Our qualitative study showed that providing What if explanations has a
positive efect on diferent aspects of a RS such as transparency, trust, user control, satisfaction,
and user experience. This paper contributes to a richer understanding of why and how to
design What if interactive explanation in RS. Quantitative studies can build forth on our work
to investigate the efect of What if explanation on the perception of and interaction with
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