### Traditional Assessment and Serious Games Approaches  
Traditional psychological assessment approaches refer to qualitative measures, such as the Adult Attachment Interview, and/or quantitative measures, such as the Adult Attachment Questionnaire or the Rosenberg Self-Esteem Scale in which respondents provide explicit and conscious information about themselves [29; 30; 31]. Although these measures are well validated and present a high internal consistency, they are showing some limitations in that they are too abstract and decontextualized from real situations and they are not able to activate specific phenomena that need to be activated in order to be manifested, such as attachment situations [32]. Furthermore, methodologically, the assessment is conducted in neutral laboratory or clinical settings to maintain control on confounding variables that can influence the veracity of the final outcomes. Finally, they are also presenting biases, such as the social desirability bias that is the tendency of self-reported respondents to answer questions in accordance with socially favorable norms to maintain a socially favorable self-presentation, affecting responses veracity [33; 34]. Recently, advances in technological systems, such as videogames and computer games, as well as the amount of time children, adolescents, and adults play computer games has significantly gone up, providing the opportunity to use them for enhancing traditional psychological assessment. Indeed, their playability and appeal led researchers to become interested in the development of applications with \"serious\" and specific goals for the evaluation and training of abilities, going beyond common entertainment [35; 36]. Serious games (SGs) are proving to be able to generate motivational engagement, due to main game features such as challenges, rewards, narrative, virtual agents, and fantasy worlds, as well as immersion and interaction, enhancing user experience. Indeed, the first computer games were supported by non-immersive systems (2D), as desktop, and the interaction was afford by keypad and mouse; more recently, SG can be experienced also through immersive systems, as head mounted display (HMD) able to completely isolate the user from reality, allowing them to explore, navigate, and interact with objects (through control sticks and gloves) in real-time as if the user was in the physical reality. Furthermore, SGs are proving to be effective to assess and train abilities adding behavioral-based information to traditional methods [37; 38; 39]. To create valid assessment in games, \"stealth\" game design is providing significant evidence mainly related to learning [40; 41]. The stealth assessment (SA) game design approach aims to implicitly measure user performance during the game without asking users to self-report information about their personality, behavior, or state. SA refers to evidence-centered design (ECD) as a conceptual framework based on three models to develop valid assessments: competency, structural, and task models [42; 43]. The competency model refers to the abilities or constructs and traits, also called unobservable indicators, that researchers want to measure using the game; the structural model identifies the multifaceted behaviors, also called observable indicators, that can reveal the theoretical abilities or constructs and traits; and the task model designs tasks or situations that can produce those behaviors related to the abilities, constructs, or traits that researchers want to measure. The SA approach has been shown to have greater predictive validity and less bias than traditional assessment [37; 43]. Indeed, SA allows the creation of several SG contexts in which participants perform a sequence of actions, reducing test anxiety and bias with respect to traditional assessment and invisibly providing a large amount of data on various ranges of individual attributes and skills [37; 43; 44].