What do we mean by engagement? 

Engagement has been conceptualized differently across fields of study; for example, in the computer science and human-computer interaction fields, engagement has been described as the experience of flow or as someone’s subjective experience, whereas in the behavioral science Field, engagement has been predominantly described in terms of usage of the digital behavioral change interventions (Perski et al., 2017). For example, engagement has been described as the “dose” participants receive or as the “adherence” to the intervention (Perski et al., 2017).