# Characteristics of a Persuasive Educational System: A Systematic Literature Review
## 2 Design and Evaluation of Persuasive Systems  
Knowing the tools used to design persuasive systems, as well as the evaluation mechanisms, allows us to know what the creation of a persuasive system implies. Regarding the design process, there are useful tools used to understand the persuasion process through technology; for example, The 8-Step Process [13], The Functional Triad [1], and The Persuasive Systems Design (PSD) model [2]. We consider it important to have a general knowledge of each one of them to contextualize ourselves in the design process. * As the name implies, The eight-step process describes eight steps to follow as best practices in the early stages of persuasive technology design. The steps to follow in the process are the following: 1. Choose a simple behavior to target. 2. Choose a receptive audience. 3. Find what prevents the target behavior. 4. Choose a familiar technology channel. 5. Find relevant examples of persuasive technology. 6. Imitate successful examples. 7. Test and iterate quickly. 8. Expand on success. The process can be envisioned in three main stages: context study, system construction, and reformulation of the system's target behavior. The first stage deals with steps 1 to 5, the second stage with steps 6 and 7, and the third with step 8. * The Functional Triad is a framework that describes three roles in which a system can be persuasive from the user's perspective: as a tool, as a medium, and as a social actor. Each role has its own techniques to persuade the user but, in general terms, a system can be persuasive as a tool by making the target's behavior easier to persuade; as a social actor, it can be persuasive by rewarding people with positive feedback; and as a medium by allowing people to rehearse the target's behavior. * The PSD model is based on the Functional Triad and is currently the most used since it helps to understand how to persuade through technology and how to execute the process. The model suggests the following three steps for the design process of a PS: 1. The first step is named \"understanding key issues behind persuasive systems\". The author of the PSD model states that a system can be analyzed and designed only after obtaining a reasonable level of understanding of seven postulates. 2. The second step analyzes the persuasion context. It determines who the persuader is, the expected type of change, the usage context, the user, the technology, the route, and the message to be sent. 3. The last step is to design the system's characteristics by writing the implementation of persuasive strategies in the form of a software requirement. Since the PSD model is the most widely used, it has also been the basis for proposing new tools to design PSs. In 2018, Ref. [14] proposed improvements for the PSD model by adding user-centered design techniques. The goal was to guide designers and developers (even researchers) with all the aspects needed to analyze user and usage context, and propose user-involving solutions. Furthermore, the framework includes three stages of the Extreme Programming (XP) methodology to coordinate the software development process. Regarding the process of evaluating PSs, it is important to understand the two different ways to evaluate them: (i) based on the system's persuasive qualities or (ii) based on its impact. The PSD model has been used as an evaluation tool to evaluate PSs based on their persuasive qualities. In addition to being a design tool, the model has been used as an evaluation tool due to the detailed list of persuasive strategies. In [15], the authors createda check-list to evaluate the persuasive qualities of a system based on the PSD model. Other proposals for evaluating persuasive systems also include the verification of implemented persuasion strategies and the usability attributes [16; 17]. Both studies proposed heuristics based on the PSD model and the usability heuristics of [PERSON] [18]. The second way to evaluate a persuasive system is through the impact generated on the user.