# Modelling and Measuring Trust in Human-Robot Collaboration
## 2 Background  
### Theoretical Foundations of Trust  
Trust is a crucial determinant of effective collaboration, in both human-to-human and human-to-machine interactions. Consequently, studies on trust modelling and measurement span a variety of disciplines, including psychology, sociology, biology, neuroscience, economics, management, and computer science [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]. These two approaches--(modelling and measuring)--share common knowledge, but with differing purposes and considerations. Trust modelling aims to depict human trust behaviour, extrapolating individual responses to a universal level, whereas trust measurement encompasses various methods. These methods include subjective ratings, which involve individuals' personal assessments of trustworthiness based on their perceptions and experiences, and objective, measurable approaches that quantify involuntary body responses to varying trust-related stimuli. While subjective ratings provide insights into individuals' subjective perceptions of trust, objective measurements offer quantifiable data that can be analysed and compared across different contexts. The multidisciplinary nature of human trust research signifies that defining a unique modelling approach is complex. Various disciplines offer distinct perspectives on trust with specific views that, when integrated, offer a holistic perspective on the definition of trust. Sociology views trust as a subjective probability that another party will act in a manner that does not harm one's interests amid uncertainty and ignorance [1], while philosophy frames trust as a risky action deriving from personal and moral relationships between entities [3]. Economics defines trust as the expectation of a beneficial outcome of a risky action taken under uncertain circumstances and based on informed and calculated incentives [4], and psychology characterizes trust as a cognitive learning process shaped by social experiences and the consequences of trusting behaviours [5]. Organizational management perceives trust as the willingness to take risks and be vulnerable in a relationship, predicated on factors like ability, integrity, and benevolence [6], and trust in international relations is viewed as the belief that the other party is trustworthy, with a willingness to reciprocate cooperation [7]. Within the realm of automation, trust is conceptualized as the attitude that one agent will achieve another agent's goal in situations characterized by imperfect knowledge, uncertainty, and vulnerability [8], while in computing and networking contexts, trust is understood as the estimated subjective probability that an entity will exhibit reliable behaviour for specific operations under conditions of potential risk [9]. In general terms, trust is perceived as a relationship where a subject (trustor) interacts with an actor (trustee) under uncertain conditions to attain an anticipated goal. In this scenario, trust is manifested as the willingness of the trustor to take risks based on a subjective belief and a cognitive assessment of past experiences that a trustee will demonstrate reliable behaviour to optimize the trustor's interest under uncertain situations [2]. This definition emphasizes several issues concerning the nature of trust:  
* A subjective belief: Trust perception heavily relies on individual interactions and the preconceived notion of the other's behaviour. * To optimize the trustor's interest: Profit or loss implications for both the trustor and trustee through their interactions reveal the influence of trust/distrust dynamics. * Interaction under uncertain conditions: The trustor's actions rely on expected behaviours of the trustee to optimize the anticipated outcome, but it may yield suboptimal or even prejudicial results. * Cognitive assessment of past experiences: Trust is dynamic in nature, initially influenced by preconceived subjective beliefs but evolving with ongoing interactions. Authors have proposed varying dimensions of trust to explain different elements of trust development.