Intersubjectivity, Joint Action and Sociality Sabrina Cipolletta a , Michael F. Mascolo b , and Harry Procter c a Department of General Psychology, University of Padua, Padua, Italy; b Department of Psychology, Merrimack College, North Andover, MA, USA; c Department of Psychology, University of Hertfordshire, Taunton, UK ABSTRACT Intersubjectivity consists of the mutual coordination, incorporation and sharing of meaning and experience between people over time. The study of intersubjectivity raises difficult conceptual and meth- odological issues. Defined as a form of mutually coordinated experi- ence, intersubjective processes are those that occur between rather than merely within persons. As such, the concept of intersubjectivity incorporates but extends beyond related concepts such as sociality, commonality, and perspective taking. To the extent that intersubject- ive processes are relational ones, their study requires the ability to analyze forms of engagement that occur between rather than merely within individual actors. We suggest that the most basic way to assess intersubjectivity involves recruiting the human capacity for intersubjective engagement itself as a primary method of psycho- logical research. Toward this end, drawing on existing studies involv- ing moment-by-moment observation of videotaped interaction, we track the developmental changes of different forms of intersubjective engagement as they occur between infants and their caregivers. Building on this work, we propose and illustrate methods for identi- fying moment-by-moment changes in sociality and intersubjective engagement as they occur in verbal and nonverbal joint action among adults. ARTICLE HISTORY Received 5 March 2019 Accepted 1 April 2020 How do people gain the capacity to identify psychological experience in themselves and in other people? The study of experience has long been a challenge to scientific psych- ology. Psychological science was founded on the value of objectivity. Invoking the con- cept of objectivity, behavior is understood as external, objective and publicly observable, while psychological experience is understood as internal, subjective and private. From this viewpoint, individuals are assumed to have privileged access to their own psycho- logical experiences (MacDonald, 2014), while the experiences of the self are inaccessible to third-person observers. Despite the intuitive appeal of these ideas, they raise deep problems: how is it possible for people to form shared representations of experiences that are by definition private? Traditional answers invoke the concepts of introspection and projection. Knowledge of one’s own experience comes from introspection: first-person experiencers “look within” themselves, identify experience, and then use words to communicate those experiences. CONTACT H. Procter harryprocter20@gmail.com University of Hertfordshire, 70 Staplegrove Road, Taunton, UK. ß 2020 Taylor & Francis Group, LLC JOURNAL OF CONSTRUCTIVIST PSYCHOLOGY https://doi.org/10.1080/10720537.2020.1805066