In the third attempt, to investigate how individuals perceive robots in power, we designed two user-studies with powerful robots. That is, we equipped robots with power resources. Since social power endows individuals the ability to influence, we designed scenarios in which the robot attempted to persuade the users. The link between power and persuasion has been investigated for a long time in social psychology. Different theories exist regarding this link, for instance, recent evidence suggests that a higher level of power leads to higher persuasion. Although other approaches are viable to make robots persuasive (as done before in other studies), we used social power strategies that have been neglected in this field. Initially, we selected reward, coercion and expert strategies due to their applicability in making more believable scenarios.
In the first study, we investigated the role of social power in persuasive social robots. In this work, we explored two types of persuasive strategies that are based on social power (specifically reward and expertise) and created two social robots that would employ such strategies. To examine the effectiveness of these strategies we performed a user-study with 51 participants using two social robots in an adversarial setting in which both robots tried to persuade the user on a concrete choice (3 coffee capsules hidden in 3 boxes). In our design, one robot attempted to persuade the users to select his coffee by giving them information about the good quality of his capsule, while the other robot tried to influence the users by giving them a reward. Also, we put the third coffee, as the control condition, which was not promoted by any of the two robots We considered five dependent variables, the selected coffee, the preferred robot, robots persuasiveness, robot perception, and how likely they are to comply with each robot in the future. The independent variable was the power strategy used by the robots. The results showed that although each of the strategies caused the robots to be perceived differently in terms of their competence and warmth, both were similarly persuasive.
Similarly, the second study  was designed to investigate the persuasiveness of social robots using two persuasive strategies inspired from social power. In this design, we used a single robot in two different conditions, plus a control condition. In this design, we used two coffee capsules with different rankings. In the first condition (reward power strategy), the robot tried to persuade the users to opt for the lower-ranked coffee by giving them a reward (a pen). In the second condition (coercive power strategy), the robot first gave a pen to the users as a reward for participating in the experiment, but later required the pen as payment for the high ranked coffee (punishment for not complying). In the control condition, the robot did not use any persuasive strategy and the users were free to select any of the two capsules. We measured the personality of the users, the robot perception, and the social power of the robots (using the Social Power Scale). The results indicated that, in the two conditions, the robot succeeded to persuade the users to select a less desirable choice compared to a better one. However, no difference was found in the perception of the robot comparing the two strategies, neither the social power level. The results suggested that social robots are capable of persuading users, especially the ones who are new to social robots. However, the collected data did not represent any significant difference regarding the other measured variables, and we aim to investigate them in a future study.
The two previous studies indicated that social power endows persuasiveness to social robots, however, this effect was tested only using a single attempt. It is not clear if the effect of social power on persuasion remains constant over a series of interactions, or it decays or even strengthens over time. Furthermore, earlier in the first step, we proposed a formalization for modeling social power for social agents. The model indicates that social power has a linear relationship with the identified parameters. For instance, an increase in the level of rewards, leads to higher social power. In other words, a higher valued reward leads to higher power and hence compliance. Also, the relationship between power level and persuasion is not clear. For instance, in case of reward power, if the higher reward leads to higher persuasion?
Hence, the last study aims to evaluate the model in application, specifically over a series of repeated interactions. In so doing, we aim to use the proposed formalization of social power using different values for the identified parameters to investigate how the model works under different circumstances.