We are delighted to present this special issue of Behaviour & Information Technology (BIT), featuring extended versions of a selection of the best papers presented at the 18th International Confere...

Anthropomorphic visual and auditory cues are two crucial design elements influencing users’ affective preference for chatbots. However, most earlier studies only focused on one of them and it is still unknown how anthropomorphic visual appearance and voice influence users’ affective preference and neural responses. In the current research, participants’ subjective preference evaluation and objective ERP responses were measured when being presented with chatbots with different visual and auditory cues. (human-like voice and mechanical voice). Subjective results indicated that consistent cues of anthropomorphic visual appearances and voices jointly evoked users’ higher affective preference for chatbots. Notably, auditory cues play a dominant role among audiovisual cues that influence users’ affective preference for chatbots. ERP results showed that low anthropomorphic visual appearances and mechanical voices jointly elicited larger P2 and P3. Additionally, chatbots with low anthropomorphic visual appearances and chatbots with human-like voices elicited larger LPP. These findings hold theoretic implications for understanding the impact of chatbots’ visual appearance and voice on users’ affective preference and provide practical insights for the design of human-chatbot interactions.

With rapid digital innovation, social support strategies are increasingly embedded in Academic Social Networking Sites (ASNSs) to shape user perceptions and behaviors. However, limited empirical research has examined how these strategies influence users’ credibility perceptions and behavioral intentions. Credibility, a key factor driving participation on ASNSs, remains underexplored in this context. This study investigates the role of seven social support strategies within the Persuasive System Design (PSD) framework. It examines their effect on credibility perceptions, as well as the effects of credibility on perceived persuasiveness and continuous use intentions. Using data from 255 ASNS users and Partial Least Squares Structural Equation Modeling (PLS-SEM), results show that several social support strategies significantly shape perceived social learning, which strongly influences credibility perceptions. Additionally, perceived persuasiveness mediates the relationship between perceived credibility and continuous use intention. The findings offer practical insights for designing ASNSs that enhance credibility, persuasiveness, and sustained engagement.

Research has shown the potential of social robots to support learning in science, technology, and language. We contribute to this field by exploring how robots can support music learning. We report on a within-subjects experiment where 50 young learners practiced the piano in the presence of a robot assuming a non-evaluative and a self-assessment enhancing role implemented in a Wizard-of-Oz fashion. We examined whether the robot can make piano practice more fun, and whether initiating self-assessment to support self-regulated learning is a useful strategy for the robot. We collected quantitative self-report data to assess fun, learning, interest, engagement, and effort. We found a direct positive effect of fun on learning in the context of musical instrument practice. Path modeling showed a positive influence of having fun on learners' attitudes, interests, and learning outcomes in music education, particularly with the self- assessment robot role exhibiting superiority.

Measurement of users’ perception and visual behaviors to anthropomorphic design cues of chatbots can improve our understanding of chatbots and potentially optimize chatbot design. However, as two typical and basic features, how chatbot appearances and conversational styles jointly affect users’ perception and visual behaviors remains unclear. Therefore, this study conducted an eye-tracking experiment to explore users’ perception and visual behaviors. Results indicate that anthropomorphic appearances and human-like conversational styles jointly increased users’ perception of chatbots’ social presence, trust in chatbots, and satisfaction with chatbots. In contrast, on users’ visual behaviors, such a joint effect was not found, although chatbots with higher anthropomorphic appearances and human-like conversational styles triggered more fixation counts and longer dwell time. These findings suggest that anthropomorphic appearance and human-like conversational style can improve users’ perception and attract more visual attention to chatbots. These findings provide theoretical contributions and practical implications for relevant researchers and designers.

In music education, staying motivated has always been a crucial goal, especially for children. Earlier research has demonstrated how social robots could help improve motivation and increase the performance of children practicing music pieces. As important stakeholders, the attitudes and expec- tations of parents and music teachers are important factors that affect children’s and their own acceptance of applying social robots in music education. In this study, a survey was created and used to assess parents’ and music teachers’ attitudes, expectations, and intentions related to using social robots in music education. The survey results suggested that parents and music teachers expect robots to act as assistive and motivating agents, give positive feedback, and schedule and structure practice sessions. Moreover, parents expect a social robot to evaluate student performance, while music teachers focus more on positive encouragement. The biggest concerns of these stakeholders are whether the robots can convey the emotional aspects of music and demonstrate how to play the instrument. The intention of using robots is positively correlated with positive attitudes towards robots in general and the positive attitude towards robots specifically in the context of music education. The current study contributes insights into parents’ and music teachers’ attitudes and expectations as determinants of their acceptance of of social robots in music education, and provides a method for measuring these attitudes and expectations.

With technology being ubiquitous in our daily lives, it is crucial to understand the factors that influence their perceived credibility. In the current research, we focus on the design of Academic Social Networking Sites (ASNSs). In order to facilitate continuous adoption and use of ASNSs, it is important to understand the factors that determine their Perceived Credibility. Using the Persuasive System Design (PSD) framework as a foundation, the study investigated which of these four key constructs (i.e. Perceived Aesthetics, Perceived Usability, Perceived Usefulness and Perceived Primary Task Support) are the most relevant determinants of the Perceived Credibility of ASNSs. In an online survey, the current research assessed this research model. The results of Partial Least Square analyses confirmed that Perceived Aesthetics, Perceived Usefulness and Perceived Primary Task Support are determinants of Perceived Credibility but provided no evidence for Perceived Usability as a determinant. Moreover, the results showed that Perceived Primary Task Support was the most relevant determinant of Perceived Credibility. Implications of these findings are discussed.

Measurement of physiological reactions to persuasive messages can improve our understanding of psychological processes of persuasion, and potentially further enhance and personalize current persuasion interventions. However, little is known about the relationship between psychophysiology and persuasive processes. This study focused on four persuasion principles: scarcity, commitment, consensus, and authority, and people's susceptibility to them. Physiological measures included the cardiovascular, respiratory, and electrodermal system, as well as facial motor systems. Psychological measures consisted of self-reported attitude towards oral care and susceptibility to persuasion (STPS). We performed a randomized within-subject experiment in which fifty-six participants viewed persuasive messages deploying the aforementioned persuasion principles to improve their oral care. Results indicated different physiological patterns during persuasion versus rest. We found no different physiological patterns in exposure to distinct persuasion principles, nor a clear correlation with susceptibility to individual persuasion principles. However, mixed model analysis illustrated that overall STPS scores help explain variance in reactivity of skin conductance level and skin conductance response, and reactivity in the zygomaticus major: lower susceptibility relates to higher reactivity. Summarizing, we have found no conclusive support for distinct psychophysiological patterns associated with different persuasion principles, although overall susceptibility seems to be reflected in physiology to some extent.

Physiological responses to persuasion can help to increase our understanding of persuasive processes, and thereby the effectiveness of persuasive interventions. However, a clear relationship between psychophysiology and persuasion is not yet established. This article investigates if peripheral physiology predicts persuasion effectiveness, and whether peripheral physiology yields information that is not represented in other predictors of persuasion. We studied physiological reactions in the cardiovascular, electrodermal, facial muscle and respiratory systems of 75 participants while they read gain- or loss-framed persuasive messages advocating increased oral health care behavior. Persuasion effectiveness was measured as pre to post intervention changes in self-reported attitudes and intentions, as well as through changes in behavioral compliance over three weeks. Overall, participants showed stronger attitudes and intentions directly after the intervention (short-term persuasion), but did not show changes in behavior or attitudes two weeks later (no long-term persuasion). On an individual level, physiological reactivity parameters yielded additional information – next to self-report measures – to predict persuasion effectiveness on attitude, intention and behavioral compliance. To conclude, our findings suggested a positive relationship between physiological reactivity to persuasive messages and subsequent attitudes, intentions and behavior, and quantified the extra personalization that psychophysiological measures might bring to persuasive messaging.

The application of social robots has recently been explored in various types of educational settings including music learning. Earlier research presented evidence that simply the presence of a robot can influence a person's task performance, confirming social facilitation theory and findings in human-robot interaction. Confirming the evaluation apprehension theory, earlier studies showed that next to a person's presence, also that person's social role could influence a user's performance: the presence of a (non-) evaluative other can influence the user's motivation and performance differently. To be able to investigate that, researchers need the roles for the robot which is missing now. In the current research, we describe the design of two social roles (i.e., evaluative role and non-evaluative role) of a robot that can have different appearances. For this, we used the SocibotMini: A robot with a projected face, allowing diversity and great flexibility of human-like social cue presentation. An empirical study at a real practice room including 20 participants confirmed that users (i.e., children) evaluated the robot roles as intended. Thereby, the current research provided the robot roles allowing to study whether the presence of social robots in certain social roles can stimulate practicing behavior and suggestions of how such roles can be designed and improved. Future studies can investigate how the presence of a social robot in a certain social role can stimulate children to practice.

To advance the research area of social robotics, it is important to understand the effect of different social cues on the perceived social agency to a robot. This paper evaluates three sets of verbal and nonverbal social cues (emotional intonation voice, facial expression and head movement) demonstrated by a social agent delivering several messages. A convenience sample of 18 participants interacted with SociBot, a robot that can demonstrate such cues, experienced in sequence seven sets of combinations of social cues. After each interaction, participants rated the robot's social agency (assessing its resemblance to a real person, and the extent to which they judged it to be like a living creature). As expected, adding social cues led to higher social agency judgments; especially facial expression was connected to higher social agency judgments.

Applications of social robotics in different domains such as education, healthcare, or as companions to people living alone, often entail that robots will act as persuasive agents. However, persuasive attempts can give rise to psychological reactance where people have negative thoughts and emotions that limit adherence to the persuader. To understand the phenomenon of reactance to robotic persuaders, we investigate the effect of social cues of an artificial agent on psychological reactance and compliance. Participants in a laboratory experiment played a decision-making game in which persuasive attempts were delivered in one of three forms: as a persuasive-text, spoken by a social robot (the SocibotTM) displaying minimal social cues, or by the same robot displaying enhanced social cues. Our results suggest that a social robot with minimal social cues invokes the lowest reactance. Remarkably, exploratory analyses indicate cross-gender effects (between robot and user) upon invoking lower psychological reactance and female participants have higher compliance than male participants.

In many future social interactions between robots and humans, robots may need to convince people to change their behavior. People may dislike and resist such persuasive attempts, a phenomenon known as psychological reactance. This paper examines how reactance, measured in terms of negative cognitions and feelings of anger, is affected by the persuading agent's social agency cues and the level of controlling language used. Participants played a decision-making game in which a persuasive agent attempted to influence their choices exhibiting high or low controlling language, and three different levels of social agency. Results suggest that controlling language will lead to increased reactance when the persuasive agent does not exhibit social cues. Surprisingly, reactance is not affected by controlling language in the same way when the persuading agent is a social robot exhibiting social cues.

This article explores the relation between consistency of social cues and persuasion by an artificial agent. Including (minimal) social cues in Persuasive Technology (PT) increases the probability that people attribute human-like characteristics to that technology, which in turn can make that technology more persuasive (see, e.g., Nass, Steuer, Tauber, & Reeder, 1993). PT in the social actor role can be equipped with a variety of social cues to create opportunities for applying social influence strategies (for an overview, see Fogg, 2003). However, multiple social cues may not always be perceived as being consistent, which could decrease their perceived human-likeness and their persuasiveness. In the current article, we investigate the relation between consistency of social cues and persuasion by an artificial agent. Findings of two studies show that consistency of social cues increases people’s recognition and recall of artificial agents’ emotional expressions, and make those agents more persuasive. These findings show the importance of the combined meaning of social cues in the design of persuasive artificial agents.

Earlier research showed that artificial social agents can influence human behavior. This article argues that, especially under certain circumstances, people are sensitive to persuasion by (artificial) social agents. For example, when people feel socially excluded, they are motivated to increase their social connections with others. It was hypothesized that socially excluded people would attribute more human-likeness and be persuaded more by an artificial agent than socially included people. These hypotheses were investigated in two studies in which participants were either socially included or excluded, after which they performed an energy-saving task while receiving social feedback from an artificial agent. Results did not support the expectation that socially excluded people ascribe more human-likeness to an artificial agent, but they did show the expected effects on behavior change, indicating the importance of including a person’s psychological state in the design of human–agent interactions. Also, in line with earlier findings, female participants were more susceptible to the agent’s feedback than male participants, indicating that a user’s gender may also determine the effectiveness of persuasive technology.

In human-robot interaction research, much attention is given to the extent to which people perceive humanlike attributes in robots. Generally, the concept anthropomorphism is used to describe this process. Anthropomorphism is defined in different ways, with much focus on either typical human attributes or uniquely human attributes. This difference has caused different measurement tools to be developed. We argue that anthropomorphism can best be described as a continuum ranging from low to high human likeness, and should be measured accordingly. We found that anthropomorphic characteristics can be invariantly ordered according to the ease with which these can be ascribed to robots.

A complex relationship exists between national cultural background and interaction with robots, and many earlier studies have investigated how people from different cultures perceive the inclusion of robots into society. Conversely, very few studies have investigated how robots, speaking and using gestures that belong to a certain national culture, are perceived by humans of different cultural background. The purpose of this work is to prove that humans may better accept a robot that can adapt to their specific national culture. This experiment of Human-Robot Interaction was performed in Egypt. Participants (native Egyptians versus Japanese living in Egypt) were shown two robots greeting them and speaking respectively in Arabic and Japanese, through a simulated video conference. Spontaneous reactions of the human subjects were measured in different ways, and participants completed a questionnaire assessing their preferences and their emotional state. Results suggested that Egyptians prefer the Arabic version of the robot, while they report discomfort when interacting with the Japanese version. These findings confirm the importance of a culture-specific customisation of robots in the context of Human-Robot Interaction.

In this paper we argue that energy conservation is largely a group phenomenon requiring group interventions to achieve change. Persuasive technology can help to provide these interventions. The present study explores the influence of group feedback and individual comparative feedback on energy consumption using an experimental simulation paradigm. To account for cultural differences in group orientation and the power of group feedback, two studies were conducted, one in the Netherlands and one in Japan, in which groups of participants received feedback on everyday tasks. As expected, Dutch participants saved more energy when individual comparison feedback was present, but not the Japanese participants. In contrast, as expected, group feedback caused Japanese participants to save more energy. Providing solely group feedback did not promote energy saving in the Netherlands. Group feedback made the Dutch save more energy only in combination with individual comparison feedback. These results suggest that persuasive technology can employ the power of feedback as a group intervention, but that relevant cultural orientations are crucial.

A fundamental characteristic of ambient persuasive technology is the ability to persuade users outside of conscious attention. One method of influencing people outside of their conscious awareness is subliminal priming: Presenting a stimulus for less than 50 milliseconds so people can not consciously perceive it but they are able to process the information unconsciously. Earlier research has shown that subliminal feedback on energy consumption leads to more optimal choices in an energy-related choice task compared with no feedback. Would subliminal feedback always be effective in influencing people's choices, or do people need to be motivated to reach a specific goal for it to work? In the current research, we investigate if persuasion by subliminal feedback comprises a goal-striving related process in which people strive for a goal and use the subliminal information to reach that goal. In an experimental study, half of the participants were primed with the goal to perform well, and the other half was not primed with this goal. Next, half of the participants received subliminal feedback in a learning task, whereas the other half received no feedback. Results indicated that participants primed with a performance goal made more correct choices in the task when given the subliminal feedback compared with given no feedback. Participants who were not primed with a goal were not influenced by this feedback. This finding indicates the need for a behavior-relevant goal to make subliminal information effective, which in turn has important implications for research and design of ambient persuasive technology.

Two experiments explored the persuasive effects of social feedback, as provided by a robotic agent, on behavioral change. Results indicate stronger persuasive effects of social feedback than of factual feedback (Experiment 1) or factual evaluative feedback (Experiment 2), and of negative feedback (especially social but also factual) than of positive feedback.

In this paper we explore a fundamental characteristic of Ambient Persuasive Technology: Can it persuade the user without receiving the user's conscious attention? In a task consisting of 90 trials, participants had to indicate which of three household appliances uses the lowest average amount of energy. After each choice, participants in the supraliminal feedback condition received feedback about the correctness of their choice through presentation of a smiling or a sad face for 150 ms. Participants in the subliminal feedback condition received identical feedback, but the faces were presented only for 25 ms, which prohibited conscious perception of these stimuli. The final third of the participants received no feedback. In the next task, participants rated the energy consumption of all presented appliances. Results indicated that supraliminal feedback and subliminal feedback both led to more correct energy consumption ratings as compared to receiving no feedback. Implications are discussed.

In this paper we explore the persuasive effects of social feedback, as provided by an embodied agent, on behavioral change. In a lab setting, two experiments were conducted in which participants had the opportunity to conserve energy while carrying out washing tasks with a simulated washing machine. The experiments tested the effect of positive and negative social feedback and compared these effects to more widely used factual feedback. Results of both studies indicate that social feedback has stronger persuasive effects than factual feedback (Experiment 1) and factual-evaluative feedback (Experiment 2). In addition, an effect of feedback valence was found, demonstrating more conservation actions following negative feedback (social or factual) as compared to positive feedback. Interestingly, especially negative social feedback had the strongest persuasive effects. The predicted perceived agency effect could not be demonstrated. These findings have several implications for theory and design of persuasive robotic agents.

Nowadays, many advertising campaigns attempt to persuade people to perform a specific behavior. In response to such messages, people can comply and adapt their behavior in the proposed direction. However, people can also experience psychological reactance, which may lead to the complete opposite of the target behavior. In the present study, we were interested in the social nature of psychological reactance. According to Social Agency Theory [12], more social cues lead to more social interaction. We suggest that this also holds for psychological reactance. We argue that there is a positive relation between the level of social agency of the source of a message and the level of psychological reactance that this message can arouse. In an online study, participants received low-controlling or high-controlling advice about energy conservation. This advice was delivered either solely as text, as text with a still picture of a robotic agent, or as text with a brief film clip of the same robotic agent. Results showed that a high-controlling advisory message resulted in more reactance than a low-controlling advisory message. Confirming our expectancies, stronger social agency of the messenger led to more psychological reactance. Implications are discussed.

Feedback can serve as an intervention aimed at reducing household energy consumption. The present study focused on the effects of agent embodiment on behavioral change through feedback. The effects of agent embodiment were studied for female vs. male users. Also factual feedback was compared to evaluative feedback. An experiment was conducted in which 76 participants used a virtual washing machine to clean laundry. They received interactive feedback about their energy consumption, from an embodied agent or from a computer. This feedback indicated the consumption level (factual feedback) or good or bad performance (evaluative feedback). The results showed that evaluative feedback, especially when it was negative, was more effective than factual feedback in reducing energy consumption, independent of the source of the feedback. Overall, for men it did not matter whether the feedback was given by a computer or by an embodied agent, but for women it did: women who interacted with the embodied agent used less energy than women who interacted with the computer.