Reactions to nostalgia-evoking content on social media platforms like Facebook and YouTube suggest an unconscious motive of ontological security, defined as a 'sense of presence in the world as a real, alive, whole, and in a temporal sense, a continuous person'. In addition to the unprecedented access to the past provided by social media, additional factors such as increasing human longevity, the acceleration of technological and social change, the expanded size and greater interconnectedness of social networks, the proliferation of directly and vicariously experienced places and the secularisation of society have contributed to a growing need for ontological security. Engagement with nostalgia-evoking social media content fulfils the need for ontological security by reintegrating memories of the past into an ongoing, self-affirming narrative or 'life story', while the digital archiving of photos and videos offers the possibility of 'digital immortality' for a virtual self that can be projected into the future.

Contemporary concerns that social media – and its hardware accomplice the smart phone – dumb down, socially isolate and cause addiction among users have historical precedents in earlier reactions to the Internet, television, radio, and even the printed word. Automated and interpretive analyses of thousands of comments on YouTube videos of products (Study 1) and television programs (Study 2) from the past suggest a link between concerns about the negative effects of smart phones and social media and autobiographical obsolescence, a sense that the lived past is psychologically disconnected from the present and irrelevant to the future. Ironically, having nostalgia experiences on social media may provide older consumers with a psychological remedy. Viewing and commenting on video material from the past helps them verify the reality of the lived past and establish its relevance to younger generations. Suspicion of the latest disruptive communication technology (DCT) may simply be part of this broader psychological restoration process.

Leximancer identified word frequencies and co-occurrences in thousands of comments on YouTube videos of TV commercials from the 60s and 70s (Study 1) and the 50s-80s (Study 2). Multiple clusters of co-occurring words suggested ontological insecurity (e.g., "old," "remember," "love," "miss") and nostalgia (e.g., "childhood," "memories," "happy," "best") as motives for viewing these videos. Leximancer generated samples of comments containing multiple key words from each cluster, and interpretive analyses of the comments in these samples revealed themes of (a) verifying and sharing autobiographical memories with others, (b) denigrating the present and embellishing the lived past, and (c) trying to connect with younger generations. Watching and discussing TV ads from childhood and early adulthood seems to help viewers reestablish continuity of the self over time and the inherent value of their autobiographical past. Exchanging comments with others on social media may restore a sense of ontological security by allowing viewers to verify their lived pasts via exchanges with others who also remember the "good old days." Public Policy Relevance StatementAs technological innovation and changes in behavioral norms continue to accelerate, memories of childhood can become psychologically distant, and individuals often feel disconnected from younger generations. As a remedy to this existential dilemma, YouTube users watch and comment on TV advertising from their youth, bonding with others who remember the same experiences, and conveying these experiences to those who were too young to remember.

Motivated reasoning suggests that climate change deniers are more likely to access and comment on unreliable online sources of information that support their existing views and political ideologies, whereas climate change believers are more likely to access more objective sources of information not necessarily related to their political viewpoints. To test this hypothesis, an R program in RStudio scraped over 68,000 user-generated comments from multiple Reddit communities (i.e., subreddits) with opposing perspectives on climate change. Leximancer identified the internet domains associated with the URL links in user comments. Consistent with a motivated reasoning explanation, comments from climate change denial subreddits tended to include URL links to content from blogs and social media pages advocating similar ideological positions, whereas comments associated with subreddits based on belief in climate change tended to include URL links to content from news media and academic journals.

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