The Effect of Personality Traits on Persuading Recommender System Users Alaa Alslaity Thomas Tran University of Ottawa, ON, K1N 6N5, Canada University of Ottawa, ON, K1N 6N5, Canada aalsl005@uottawa.ca ttran@eecs.uottawa.ca ABSTRACT attitude. Incorporating persuasive features to these systems, Persuasive Recommender System is a relatively new however, is gaining increased attention in the literature; research direction that emphasizes on using persuasive recent researches have begun using some persuasive approaches to increase user’s acceptance of the approaches to tailor users’ decisions toward desired recommendations. Recent studies have demonstrated the products (energy-saving products, for instance [14]). Also, feasibility of deploying the six persuasive principles of recent studies have shown evidence of the feasibility of Cialdini as explanations besides the recommended items. including persuasive statements as explanations, along with These principles, however, should not be treated in a one- the recommended items [6]. The main goal of this research size-fits-all approach. Instead, they should be deployed in a direction is to increase users’ acceptance of the personalized manner. The factors that help to personalize recommended items. these principles for the users of recommender systems have not been fully explored. To fill this gap, this paper At the beginning of the current decade, Yoo et al. [18] investigates one of these factors, which is personality traits. introduced the conceptual framework for persuasive RS, In particular, it explores the influence of the Big Five which is adapted from the communication-persuasion Personalities on recommender system users’ susceptibility paradigm [18]. This framework suggests that the interaction to Ciladini’s persuasive principles. The study contains two between an RS and its users is like a communication parts; the impact of personality traits as an independent process, which can be convincing based on different variable, and the impact of personality traits in conjunction factors. The framework also outlines the relationship with the application domain. We explored these factors between the key constructs of a persuasive RS, which are through a questionnaire disseminated online. The analysis the source (the RS itself), the message (the of the data received from (279) responses shows that recommendation), the target (the user), and the context. personality traits are an important factor that influences the After introducing the concept of persuasive RS, there efficiency of the six principles of Cialdini. Moreover, the became increasing attention toward this idea. Most of the effect of personality traits becomes more significant if they effort in this research is emphasized around the third are considered in combination with the application domain. construct (i.e., the target) while they ignored other constructs. In particular, the current work is concentrated Author Keywords around investigating how users’ characteristics affect their Persuasive Recommender System; Big Five Personality; persuadability to different persuasive principles. Six Weapons of Influence. There is a wide range of persuasive principles introduced CSS Concepts by the psychologists. Among these principles, the six • Human-centered computing ~ Interaction design ~ principles of Cialdini [4] (discussed in section 2.1) are the Interaction design theory, concepts and paradigms. most commonly used in the persuasive technology area. INTRODUCTION Researchers have recently started investigating how users We can define Persuasion as influencing people’s respond to these six principles. Nonetheless, a limited behaviours or attitudes without any deception or coercion number of researches discussed the influence of users’ [4]. Persuasive Technology (PT) is a technique that uses personalities on the effect of these principles, and most of human psychology to change people’s behaviour or these researches were not designed for the RS area. attitude[1]. Recommender Systems (RSs) are software Besides, the existed studies discuss the impact of systems that help people to find information, products, personality in isolation of other factors, such as the services and more based on their interests or preferences application domain. This paper aims to fill this gap by [4]. Based on these definitions, RSs cannot be considered as investigating the effect of personality traits and their PT because RSs are typically designed with the primary interaction with the application domain on RS user’s goal of assisting people in deciding not to change their susceptibility to the six principles of Cialdini. To do so, we deployed an online questionnaire that consists of two main Copyright © 2020 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). parts; personality test and persuasion test. The persuasion IntRS '20 - Joint Workshop on Interfaces and Human Decision Making for part is divided into three sections, which are the Recommender Systems, September 26, 2020, Virtual Event. eCommerce domain, the movie domain, and the general (no domain) sections. In each section, participants were asked of scarce things, and they consider these things as more to rate six sentences that represent the Cialdini’s principles. valuable. Displaying numbers of availability for products is The main goal of this study is to answer the following an example of implementing this principle. eCommerce research questions: websites (e.g., Amazon) use this principle by providing a limited-time-only promotion, which is often presented as a • RQ1: Do personality traits of RS’s users affect their countdown timer showing the time remaining before the response to Cialdini’s principles of persuasion? offer expires. The next principle, Authority, indicates that • RQ2: To what extent does a user’s susceptibility to people are more inclined to follow others who have different persuasion principles affected by the legitimate authority. For instance, it is more likely to give combination of the user’s personality trait and the change for a parking meter to a stranger if she wears a recommender’s application domain? uniform rather than casual clothes, and it is more likely to This study is different than the previous studies in two buy a toothpaste if a well-known dentist recommends it. ways: first, it is designed and deployed for a particular The fourth principle, Social Proof, means that people tend application, namely Recommender Systems. Second, it to do what others do. When people are uncertain, they look discusses the effect of users’ characteristics (personality to the actions of others to decide. Widespread deployment traits) in conjunction with context characteristics of this principle is checking the reviews of others. For (application domain), instead of considering users’ aspects instance, when people want to book a reservation in a in the separation of other factors. Our results show that: 1) resort, they usually check out the reviews of that resort. users’ personalities affect their responses to the six This principle is widely implemented in the computerized persuasive principles, 2) the context in which these system, and it is implemented in different ways, such as personalities interact with the system plays an essential role showing ratings, emphasizing the number of followers or in changing users’ responses to these principles. fans, or presenting testimonials. The fifth principle is called The rest of this paper is organized as follows: Section 2 Liking, and it states that people are most likely to accept the provides a brief introduction about persuasive principles request made by those that they like. For instance, people and personality traits, and it discusses the related work. may prefer one store over the other only because they like Section 3 talks about the study design. Then the results are the employees in that store. In online communication, you analyzed in section 4. Discussion and design guidelines are also need your customers (or users) to enjoy your service. provided in section 5. Finally, section 6 concludes the So, the service or product should be presented attractively. paper. The last principle is Commitment. It indicates that people tend to be consistent with the things they have previously BACKGROUND AND RELATED WORK said or done. The basis of this principle is that if a person In this section, we introduce the main concepts used in this committed to do small requests, it will be easier to persuade work, which are persuasive principles and personality traits. them to do larger requests. Commitment is implemented Then we discuss the related work. online by different means, such as asking the customer to Persuasive Principles test a new feature in your application for free and to write a In the literature of social sciences, there are various review about it. If the customer used and wrote a good persuasive principles. For instance, the forty (40) principles review of the service, then she is more likely to continue of Fogg [4], over 100 groups of persuasive strategies by using this service as a kind of commitment. Kellermann and Tim [9], and the six principles of Cialdini These principles provide approaches that cause one person [6]. In this study, we deployed the Cialdini’s principles to say yes to another one. That is, appropriately (a.k.a. the six weapons of influence). We considered these implementing these principles can increase the acceptance principles because they have been widely used in the of your requests, or your products. literature, and they have been verified as global persuasive approaches [14]. Also, these principles “provide a solid Personality Traits framework in order to investigate the persuasive power of Psychologists have extensively studied humans’ messages as peripheral cues in recommender systems” [14]. personalities and their characteristics. The Big Five Model The six weapons of influence are Reciprocity, Scarcity, (a.k.a the Five-Factor Model, FFM) [17] is the most widely Authority, Social Proof (or Consensus), Liking, and accepted personality theory in the psychology literature. It Commitment (or Consistency). is a hierarchical organization of the personality traits of humans. The FFM contains five core factors, usually known Reciprocity means that people have an obligation to give by the acronym CANOE or OCEAN. Following are these back to others what they have received first or to return five factors, along with their adjectives (or facets) [9]: favours. For instance, if your friend sent you a birthday gift, then you owe that friend a future gift. This principle is used • Openness: Artistic, Curious, Imaginative, Insightful, in many computerized systems where they give new users a Original, and Wide interest. gift (such as a voucher or a free service for a limited time). • Conscientiousness: Efficient, Organized, Planful, The second principle, Scarcity, states that people want more Reliable, Responsible, and Thorough. • Extraversion: Active, Assertive, Energetic, Enthusiastic, conclusion that personality traits may affect people’s Outgoing, and Talkative. susceptibility to the six weapons of influence. However, a • Agreeableness: Appreciative, Forgiving, Generous, Kind, recent survey by Alslaity and Tran [3] compared the results Sympathetic, and Trusting. of these three studies. They found that although these • Neuroticism: Anxious, Self-Pitying, Tense, Touchy, studies share the same general conclusion, their results are Unstable, and Worrying. not consistent to a high degree. Thus, the authors suggest that other factors that may affect users’ persuadability These five factors are known as relatively stable; they are should be discovered. stable throughout individuals’ lives, with some slight exceptions. A study by Soto & John [15] investigated the As a response to their call, Alslaity and Tran investigated developmental trends of the Big Five traits. They found that the effect of application domain on the susceptibility of some factors are increased or decreased slightly with ages. RS’s users to the six weapons of influence [3]. Based on a However, the researchers concluded that the changing study of (107) participants, they compared the effect of the trends were more in the facets rather than in the Big Five six principles on two RS domains, namely, eCommerce and traits. Movie RSs. The results indicated that the application domain is an essential factor that should be considered Related Work when designing a persuasive RS. To the best of our This section highlights the most recent studies related to our knowledge, this is the only study that discusses the effect of study. Thus, the section does not focus on how to the domain on RS users’ susceptibility to the six weapons incorporate persuasive capabilities to RSs. Instead, it of influence. discusses the works that investigate the relationship between the six weapons of influence on one side, and the Despite the existence of some research in the area of big five personalities and the application domain on the personality and persuasiveness in RS, the literature still has other side. the following limitations: first, most of the work focus on a single factor (mainly users’ characteristics) while ignoring Some researchers discussed the susceptibility of different other important factors. Second, they discuss a single factor groups to the Cialdini’s principles. For instance, Oyibo et in isolation of other factors that may have a significant al. [11] investigated Nigerians’ vulnerability to the six effect if combined (i.e., if the interaction effect is principles of Cialdini. They also discuss the effect of gender considered). Our work aims to fill this gap by investigating on Nigerians responses to these principles. The study found the influence of personality traits and the application that Nigerians are susceptible to all principles, and gender domain of RSs on the performance of the six principles of affects their susceptibility. In another study [12], Oyibo et Cialdini. The next section presents the design of this study. al. provided a comparative analysis of the Nigerians’ susceptibility to persuasive strategies compared to STUDY DESIGN Canadians. They found that the vulnerability of Nigerians is Our study is based on a questionnaire that consists of two different than the Canadians for all strategies except for main sections: personality test, and persuasion test. In the Commitment strategy. personality test, we deployed the Big Five Inventory (BFI), which is one of the most popular questionnaires for the Up to our knowledge, the feasibility of using persuasive FFM. It was introduced in the late 1980s [4]. The inventory statements along with the recommendations has been is known as BFI-44 because it consists of 44 short-phrase introduced by Gkika and Lekakos [6]. They deployed items. On average, the BFI-44 needs about five minutes to persuasive strategies as explanations in RSs. In particular, be answered. The second section (the persuasion test), they developed RS for their study, and they incorporated consists of three parts that represent different application the six weapons of influence as statements beside every domains, which are: 1) eCommerce domain, 2) Movie recommended item. Then they asked the participants to rate domain, and 3) a general part (i.e., it is not tailored to a each sentence based on how it may affect their decision to particular domain). Each of these subsections contains six watch the recommended movie. The results showed that persuasive cues (or statements) that represent the six using persuasive principles as explanations may affect the weapons of influence. We selected the eCommerce and decision of RS’s users to accept the recommended movie. Movie domains because they are of the most known The research in the direction of the relationship between applications of RSs. Also, they are widely used such that a personality traits and the six weapons of influence is very high portion of the people is familiar with both relatively limited [13], especially in the area of RSs. Three domains. This popularity makes it easier for us to reach a recent studies (Oyibo et al., [13], Alkış and Temizel [2], sufficient number of participants who can complete all parts and Sofia et al., [14]) discussed the effect of the big five of the questionnaire, which is necessary for the within- personalities on users’ susceptibility to the six weapons of subject design of this study. influence. The main difference between these three studies It is noteworthy to mention that we adopted the persuasive is the sample of study (i.e., the number and the origins of explanations designed by Sofia et al. [14] to develop our the participants). The three studies shared a general persuasive cues. Mainly, we used the same statements used Principle Domain Cue Reciprocity eComm A friend of you, who bought the item that you suggested to him/her in the past, recommends you this item! Movie A Facebook friend, who saw the movie that you suggested to him/her in the past, recommends this movie! General Giving you something for free (e.g., samples, gift, or free delivery) Scarcity eComm The recommended item will be available for two months only! Movie The recommended movie will be available for two months only! General Display a countdown, beside an item, indicating the time remaining for an offer on that item Authority eComm The recommended item won 3 prizes as the best-manufactured product! Movie The recommended movie won 3 Oscars! General Presenting an image of an expert uses the recommended item (ex: a doctor suggests particular exercises for his/her patients, or a security guard uses the recommended security lock) Social Proof eComm 87% of users rated the recommended item with 4 or 5 stars! Movie 87% of users rated the recommended movie with 4 or 5 stars! General Presenting the “best sellers” or the “most watched” items. Liking eComm Your Facebook friends bought this item! Movie Your Facebook friends like this movie! General Well designed (Fancy and professional) website’s interface and product’s presentation. Commitment eComm This item belongs to the kind of items you usually buy. Movie This movie belongs to the kind of movies you enjoy watching. General Using “add to wish list” option. Table 1. Persuasive cues used in the questionnaire (eComm = eCommerce) in [14] for the movie RS. Then, we used the same We built and disseminated the questionnaire online using convention to design persuasive cues for the eCommerce the “SurveyMonkey1” website. We followed a within- RS. We adopted the study of Sofia et al. because the subject design, where we asked each participant to authors followed a robust approach to develop their complete all parts of the questionnaire. The participants persuasive statements; they relied on three experts in the were recruited through different means, including paper persuasive technologies and seventeen experts in the posters posted and online channels (such as emails and domain of information systems and marketing to come up social media). We received 329 responses. After filtering with these explanations. Also, this study is the most related the responses by removing incomplete records, we retained one to ours as it is designed for the same application, a total of 279 responses. Table 2 summarizes the namely recommender systems. For the general part, we demographic information of the participants. relied on persuasive techniques that are known as practical implementations of Cialdini’s principles. Table 1 Subject (count, percentage) summarizes the persuasive cues that we used for the three Ages 16-25 (53, 19%), 26-35 (129, 46%), 36-45 parts. (59, 21%), 46+ (38, 14%) Each cue is followed by a seven-point Likert scale. The Gender Male (177, 63%), Female (98, 35%), seven scales are distributed as follows: 1 to 5 options are preferred not to mention (4, 2%) scaled from very low to very high effect. Zero (0) indicates Continent Asia (75, 27%), Europe (13, 5%), North no effect, and (-1) means a negative impact. The users were America (186, 67%), South America (2, asked to give a rating for each cue. The rating reflects the 1%), Oceania (3, 1%) impact of the cue on their acceptance of a recommendation. Particularly, the participants were asked to imagine that Table 2. Demographic Information (N=279) they use an RS. Then they need to rate each cue based on the question: “To what extent do you think that each of the following statements will influence your decision to buy an item (or to watch a movie) recommended to you?” 1 https://www.surveymonkey.com/ DATA ANALYSIS varies from one personality to another. The figure also This section discusses the results of our study. It is divided shows that Agreeable people are the most susceptible to into two subsections according to our research questions; three persuasive principles, which are Reciprocity, Social first, it discusses the effect of personality traits in isolation Proof, and Commitment. Extrovert people are the most of other factors. Then, it examines the interaction between vulnerable to Authority and Liking principles. personality traits and the application domain. The ANOVA analysis shows that the differences between For the results significance test, we deployed the Analysis the five personalities regarding the Reciprocity principle are Of Variance (ANOVA), which is a set of statistical models. significant [F = 4.378, P = 0.002]. A Tukey posthoc test ANOVA analysis is mainly used to investigate the revealed significant pairwise differences between differences between groups in a sample. For ANOVA Agreeableness and each of Conscientiousness and analysis, the persuasive principles are considered as the Openness. The test also shows that the mean rating of dependent (or within-subject) variable, while the other two Agreeable people is 0.7 and 0.85 more than Conscientious factors (i.e., Personality traits and application domain) are and Open people, respectively, which means that included as independent variables. The significance level Agreeableness is more vulnerable to the Reciprocity (α) is set to be (0.05) for all ANOVA analysis. principle. Regarding the other principles, the data did not The reliability of the results was measured by McDonald’s provide enough evidence that the differences are omega (ω) reliability test. The McDonald’s omega statistically significant (as illustrated in Table 4), but it reliability test is the non-parametric equivalent of shows that there are differences. This conclusion is not Cronbach’s alpha (ρ) reliability test [5]. The (ω) results surprising, taking into consideration that the personality indicate that our data is highly reliable (ω >= 0.7) for traits represent continuums; Individuals may fall anywhere Reciprocity and Scarcity, and it is moderately reliable for in the continuum for each trait. the remaining principles (ω >= 0.55). Table 3 depicts the persuasion profile for each personality. The effect of Personality Traits By persuasion profile, we mean the order of the persuasive This section answers our first research question; it discusses principles. That is, a persuasion profile shows the order of the relationship between personality traits of RS’s users and the persuasive principles based on their ability to persuade the six persuasive principles. Also, it shows which the corresponding personality; Each row in Table 3 persuasive principle is more effective for each personality represents the persuasion profile of the corresponding trait. personality. The principles are ordered descendingly from the most influential principle (order 1) to the least Figure 1 depicts the average ratings for the persuasive influential (order 6). For instance, the first row of Table 3 principles grouped based on personality traits. The figure depicts the persuasion profile of the Extraversion shows that all means are larger than the neutral value personality. It shows that Liking is the most influential (Zero), which means that all personalities are susceptible to principles, followed by Reciprocity, Authority, Scarcity, the six principles. The degree of susceptibility, however, Social Proof, and finally, Commitment (which is the least 3.5 influential one). 3 As general observations, Table 3 indicates that Reciprocity 2.5 and Liking are the most influential principles, where 2 Mean Reciprocity is more influential than Liking. On the other 1.5 side, Scarcity and Commitment are the least influential for 1 Agreeableness and Extraversion, respectively, where 0.5 Authority is the least influential strategy for the remaining 0 three personalities. Besides, the table depicts some similarities between the persuasion profiles. For instance, four out of six principles occupy the same order in each of Extraversion Agreeableness Conscientiousness Neuroticism Openness the following pairs of personalities: Agreeableness & Conscientiousness, Conscientiousness & Neuroticism, and Figure 1. Mean rating based on the personality traits Conscientiousness & Openness. Reciprocity Scarcity Authority Social Proof Liking Commitment F-value 4.378 0.89 0.765 1.627 0.908 0.939 P-value 0.002 0.47 0.549 0.168 0.46 0.442 Table 4. ANOVA results based on the effect of the personality traits Personality Reciprocity Scarcity Authority Social Proof Liking Commitment Extraversion 2 4 3 5 1 6 Agreeableness 1 6 5 3 2 4 Conscientiousness 1 5 6 3 2 4 Neuroticism 1 4 6 3 2 5 Openness 1 5 6 4 2 3 Table 3. Persuasion profiles based on the five personalities The results presented in this section suggest that users’ application domain). As we have mentioned above, recent responses to the Cialdini’s principles diverge based on their researchers have found that the application domain is an personality traits. This divergence becomes more essential factor that may affect the persuadability of the significant for users’ responses to the Reciprocity principle persuasive principles [3]. Therefore, instead of studying the as the ANOVA analysis showed. The next section adds up impact of personality traits in isolation of other factors, this into this section by discussing how users’ personalities subsection investigates how the interaction between affect their reactions to Cialdini’s principles in different personality traits and the application domain affects users’ application domains. vulnerability to the persuasive principles. The Interaction with the Application Domain Figure 2 depicts a comparison between users’ responses to The previous section shows that there are some differences the persuasive principles in the eCommerce domain in the effect of personality traits on users’ responses to the compared to the movie domain. The figure contains five persuasive principles. This section answers the second charts; each chart represents the results regarding one research question; It adds another dimension to the analysis, personality. The y-axis shows the mean values, while the x- which is the persuasive context (presented by the 3.5 4 3.5 3 3.5 3 2.5 3 2.5 Mean 2 2.5 Mean Mean 2 1.5 2 1.5 1.5 1 1 1 0.5 0.5 0.5 0 0 0 eCommerce Movie eCommerce Movie eCommerce Movie (a) (b) (c) 4 4 3.5 3 3 2.5 Mean Mean 2 2 1.5 1 1 0.5 0 0 eCommerce Movie eCommerce Movie (d) (e) Figure 2. Mean rating based on the personality traits and application domain; a) Extraversion, b) Agreeableness, c) Conscientiousness, d) Neuroticism, e) Openness. axis shows the persuasive principles. For each principle, to a high extent. Third, in the eCommerce domain, Liking there are two columns; one represents the mean rating in the and Scarcity are the least and the second least influential eCommerce domain while the other is for the movie strategies for all personalities. Forth, Commitment is the domain. most influential strategy for all personalities in the Movie domain. The common observation between the five charts in Figure 2 is that the means of all persuasive principles are different. To test the significance of the interaction between For instance, in regard to the Agreeableness personality personality traits and the application domain, we deployed (Figure 2-b), the means for all principles vary from one the Repeated Measure ANOVA (RM-ANOVA). As Table 6 domain to the other; Reciprocity and Social Proof were depicts, we found that the interaction between personality rated slightly higher in the eCommerce domain, while the traits and the domain of RSs have a statistically significant other four principles were rated higher in the movie effect on users’ susceptibility to three persuasive principles; domain. The only two exceptions to the observation namely Reciprocity (F= 2.296, p = 0.05), Scarcity (F = mentioned above are related to the Extraversion personality 2.897, p = 0.023), and Liking (F = 2.305, p = 0.049). (Figure 2-a); the figure shows that Scarcity and Authority Comparing to the results of the previous subsection, we can have similar means in both domains; the other four say that the impact of personality traits, in term of their principles have different means, though. responses to the six principles, become more significant if it is studied in combination with application domains. This Table 5 depicts the persuasion profiles for each personality section shows that the differences between personalities are over both domains (eCommerce and Movie). This table has statistically significant for three principles, while the a similar structure to Table 3. The only difference is that the previous section shows that the results were statistically table is divided horizontally into five parts based on significant for one principle only. These results suggest that personality factors. Each of these five parts is divided into there is a more significant effect of the personality traits two rows that represent the eCommerce (eComm) and the when they are considered in combination with the movie domains. For instance, the first row shows that application domain. Social proof is the most effective strategy for Extraversion personality in the eCommerce domain, and Commitment is DISCUSSION the most influential in the movie domain. Personalized recommendations have shown great success in the RS area; Giving suggestions that are tailored to every Several points can be inferred from Table 5; first, it shows user, have increased users’ acceptance of the that in most of the cases, the persuasion profiles in the recommendations. An important question that may arise eCommerce domain are different than that for the movie here is, “would persuasion still be useful if the domain, although they are for the same personality traits. recommended list of items is already personalized?” the More precisely, the table shows six congruent cases only answer to this question would be “yes.” In other words, the (for readability purposes, we distinguished these cases by persuasive principles focus on “how to recommend” instead the bolded text). Second, the persuasion profiles for of “what to recommend.” Persuasive principles could stand Agreeableness and Conscientiousness personalities are as a cutting-edge to reduce users’ hesitation toward making entirely different. That is, none of the persuasive principles a final decision. occupies the same order in both profiles. For the other three personalities, the table shows that their profiles are different Personality Domain Reciprocity Scarcity Authority Social Liking Commitment Proof Extraversion eComm 3 5 2 1 6 4 Movie 4 5 3 2 6 1 Agreeableness eComm 2 5 4 1 6 3 Movie 4 6 3 2 5 1 Conscientiousness eComm 2 5 4 1 6 3 Movie 4 6 3 2 5 1 Neuroticism eComm 3 5 4 1 6 2 Movie 2 5 4 3 6 1 Openness eComm 1 5 4 2 6 3 Movie 3 6 4 2 5 1 Table 5. Persuasion profiles; the interaction between Personality & Domain and Persuasive principles Reciprocity Scarcity Authority Social Proof Liking Commitment F-value 2.296 2.897 1.018 0.25 2.305 1.12 P-value 0.05 0.023 0.398 0.91 0.049 0.348 Table 6. RM-ANOVA based on the effect of the interaction between personality traits and the domain Our results show that RS users are vulnerable to all of persuasive approaches on a percentile basis. That is, for Cialdini’s principles. The results also show that personality each personality trait (T), we use the persuasive traits can be an essential factor that may influence the principle (X) with percentage (PTX) and principle (Y) decisions of RS users. That is, users’ personality is an with percentage (PTY), and so on. This solution requires important factor that should be considered when we design a study to find the correct percentages to be used. a persuasive RS. It is noteworthy to mention that the • Personality traits are more effective when combined ANOVA results did not give enough evidence to reject the with other factors. The previous section demonstrated null hypothesis for some cases. Besides, our study that treating the same personality in different contexts considered two recommendation areas only. Accordingly, could change its behaviour. Accordingly, we we suggest that wider studies that considers more recommend considering the interaction between recommendation domains are still required to generalize personality traits and other factors (the application these results. domain in particular). Other factors (such as culture, age, etc.) could also be useful if they are combined The following subsection provides general tips for with personality traits. However, we are not aware of designing persuasive RSs. We inferred these tips based on any study that considered this combination in the RS our analysis. domain. Design Guidelines The previous section answered the research questions by CONCLUSIONS AND FUTURE WORK presenting the results obtained from our study. It shows that The use of persuasive principles has been recently users’ personalities may affect their responses to the introduced to the RS area, and it has shown promising persuasive principles, and the effect of personality traits results in terms of increasing users’ acceptance of the becomes more significant if it is considered in combination recommendations. These principles should be personalized with the domain of the recommendation. Based on these in order to improve their persuasiveness. As a first step to results, this section provides general guidelines to design personalize them, we need to explore the factors that may persuasive RSs. help in this personalization process. Our work explores the effect of personality traits and the application domain on • Personality traits are an essential factor that should be RSs users’ susceptibility to Cialdini’s principles of considered when we design a persuasive RS. The influence. It also explores the persuasive profiles for each results show that the influence level of the six personality trait under two application domains. The principles varies from one personality to another. So, a analysis of the results received from (279) responses to our one-size-fits-all approach should not be used when we questionnaire revealed that personality traits affect users’ design a persuasive RS. Instead, an RS designer should responses to the persuasive principles, and this effect consider users’ personalities in order to select the becomes more significant if we considered the interaction correct influencing approach to the right person. between personality traits and the application domain. • Personalities are not treated in a black-and-white Based on these results, we suggested some general basis. As the results shown, our analysis did not show guidelines that should be considered for designing a clear evidence that differences between personalities personalized persuasive RS. are statistically significant for most of the cases. Thus, As future work, we are working on exploring other factors we do not recommend treating users’ personalities on a that are expected to affect RS users’ responses to the Six binary basis if your design depends on the FFM. weapons of influence. These factors include, but not limited Instead, we suggest two solutions; first, consider the to, users’ age, gender, and culture. Also, we should combination between the traits, such that categorizing investigate the interaction between all (or part of) these the users as a combination between the existence and factors, and how this interaction may affect the influence of the absence of traits. Promising work in this direction persuasive principles. Besides, it is necessary to study the is introduced by Sofia et al., [14], where they suggest impact of the persuasive principles in other RSs domains, paths of combined traits that lead to a high acceptance such as music and education RSs. of each persuasive principle. This work, however, still limited, such that it does not consider all the combinations of traits. The second solution is to deploy REFERENCES [1] Adnan M, Mukhtar H, Naveed M. Persuading students [11] Oyibo K, Adaji I, Orji R, Vassileva J. The for behaviour change by determining their personality Susceptibility of Africans to Persuasive Strategies: A type. In2012 15th International Multitopic Conference Case Study of Nigeria. InPPT@ PERSUASIVE 2018 (INMIC) 2012 Dec 13 (pp. 439-449). IEEE. (pp. 8-21). [2] Alkış N, Temizel TT. The impact of individual [12] Oyibo K, Adaji I, Orji R, Olabenjo B, Vassileva J. differences on influence strategies. Personality and Susceptibility to Persuasive Strategies: A Comparative Individual Differences. 2015 Dec 1;87:147-52. Analysis of Nigerians vs. Canadians. In Proceedings of [3] Alslaity A, Tran T. On the Impact of the Application the 26th Conference on User Modeling, Adaptation and Domain on Users’ Susceptibility to the Six Weapons of Personalization 2018 Jul 3 (pp. 229-238). ACM. Influence. In International Conference on Persuasive [13] Oyibo K, Orji R, Vassileva J. Investigation of the Technology 2020 Apr 20 (pp. 3-15). Springer, Cham. Influence of Personality Traits on Cialdini’s Persuasive [4] Cialdini RB. Harnessing the science of persuasion. Strategies. In PPT@ PERSUASIVE 2017 (pp. 8-20). Harvard business review. 2001 Oct 1;79(9):72-81. [14] Sofia G, Marianna S, George L, Panos K. Investigating [5] Fogg BJ. Persuasive computers: perspectives and the role of personality traits and influence strategies on research directions. In Proceedings of the SIGCHI the persuasive effect of personalized recommendations. conference on Human factors in computing systems In 4th Workshop on Emotions and Personality in 1998 Jan 1 (pp. 225-232). Personalized Systems (EMPIRE) 2016 Aug (p. 9). [6] Gkika S, Lekakos G. The persuasive role of [15] Soto CJ, John OP. Development of Big Five Domains explanations in recommender systems. In the 2nd intl. and Facets in Adulthood: Mean‐Level Age Trends and Workshop on behaviour change support systems (bcss Broadly Versus Narrowly Acting Mechanisms. Journal 2014) 2014 May 22 (Vol. 1153, pp. 59-68). of Personality. 2012 Aug;80(4):881-914. [7] Jannach D, Zanker M, Felfernig A, Friedrich G. [16] Starke AD, Willemsen MC, Snijders C. With a little Recommender systems: an introduction. Cambridge help from my peers: Depicting social norms in a University Press; 2010 Sep 30. recommender interface to promote energy [8] John OP, Naumann LP, Soto CJ. Paradigm shift to the conservation. In Proceedings of the 25th International integrative big five trait taxonomy. Handbook of Conference on Intelligent User Interfaces 2020 Mar 17 personality: Theory and research. 2008 Aug (pp. 568-578). 5;3(2):114-58. [17] Tupes, Ernest C., and Raymond E. Christal. “Recurrent [9] Kellermann K, Cole T. Classifying compliance gaining personality factors based on trait ratings.” Journal of messages: Taxonomic disorder and strategic confusion. Personality 60.2 (1992): 225-251 Communication Theory. 1994 Feb;4(1):3-60. [18] Yoo KH, Gretzel U, Zanker M. Persuasive [10] McCrae, Robert R., and Oliver P. John. “An recommender systems: conceptual background and introduction to the five‐factor model and its implications. Springer Science & Business Media; applications.” Journal of personality60.2 (1992): 175- 2012 Aug 17. 215