The dissertation is devoted to development of conceptual, theoretical and methodological bases of subjectness activity development of social networks adult users, as well as corresponding technologies. The definitions of the following concepts are given: "subject", "subjectness", "representative subjectness", "subjectness activity", "structural organization of the subjectness activity", "levels of subjectness activity development", "properties of subjectness activity". Positive and negative properties of the subjectness activity are outlined. The psychological peculiarities of subjectness activity in social networks are revealed. Psychological peculiarities of the subjectness activity in social networks are: communication, rapid acquisition of social capital, egocentrism, creating of own, or joining specific virtual "matrix", hedonism, procrastination; receiving attention and status, etc. Depending on the expected outcome, these psychological features of subjectness activity can be interpreted as positive, ambivalent, or negative. A psychological model of subjectness activity has been developed, which outlines the structural organization, interconnections and the main stages of subjectness activity. The key components of the subjectness structural organization is defined: formation and achievement of personal goals, motivation to self-development; intellectual initiation (reflection and introspection, determination of thinking) and other metacognitions; self-sufficiency; social activity; freedom of choice and responsibility for it; initiative; self-realization; communicativeness, predictive thinking. We have also identified the main causes and threats of loss of subjectness, decreased subjectness activity, and the possibility of its loss. Identified features of subjectness activity on social networks, its tendencies and threats of subjectness are important in terms of creating technology of its development, because without taking into account these aspects, the effectiveness of technology is significantly reduced, and subjectness activity can be changed to reactivity or passivity. The theoretical and methodological basis of the research on the level of subjectness activity of social networks users are generalized and defined. The following experimental methodics have been developed, described, and used in an empirical study: the "Questionnaire of Self-Goal setting" and in two versions, the "Questionnaire on the subjectness activity level", which is designed to determine the level of subjectness activity of social network users. It is shown that there are correlations between the development of subjectness activity and the level of motivation for self-development and development of intellectual initiation, other intellectual metacognitions and components.
