Despite variation in their social needs and experiences, all humans require social connections to thrive. When humans lack fulfilling connections, they experience loneliness. However, while seemingly simple, loneliness is a multidimensional construct arising from varied social deficiencies and leading to varied psychological experiences. This chapter reviews the literature on loneliness, describing what it is, why we experience it, its prevalence and consequences, and what is being done globally to address it. In doing so, we highlight the considerable impacts of loneliness on individuals and society, its complexity, and the opportunities for future work. We close acknowledging the significant advancements made in loneliness research over the past several decades and highlight how this knowledge is being mobilized to advance the prevention and treatment of loneliness. In doing so, we hope this chapter serves as a useful starting point for understanding the problem of loneliness and the challenge of addressing it.

The current chapter focuses on basic properties of communication that inform the ways that the study of communication and the study of relationships intersect. These properties include interdependence (the idea that messages simultaneously influence and are influenced by messages that precede and follow them), reflexivity (the notion that communication creates and is constrained by structure), complexity (the concept that communication conveys multiple messages and functions at different levels of analysis), ambiguity (the notion that any given message has various meanings), and indeterminancy (the idea that messages can have multiple and diverse outcomes on relationships). Research on relationship narratives, message features, multiple goals, and message processing, among other topics, is reviewed and challenges for researchers who study communication and relationships are discussed.

In this chapter I focus on the nature of theories in the social sciences, some philosophy of science behind the validation of theories (e.g., falsifiability, approaches to deciding the value of evidence for/against a theory), and some issues to consider with respect to the research process and theory development and evaluation. I discuss the value of deconstructing theories to assess their core and auxiliary assumptions and determine aspects of a theory that have yet to be examined. I also discuss modern approaches to assess the evidentiary value of this body of research. I suggest that in our interdisciplinary field, researchers should consider generating hypotheses, as well as research explorations, through carefully evaluating and questioning the assumptions of the theories typically applied in the study of personal relationships. This discussion includes the use of modern approaches such as computational models. The overarching theme of the chapter is that as a field we need to evaluate and develop our theories using some recommendations put forward for decades combined with recently developed techniques in order to advance our theories beyond vague verbal statements that are interesting yet not precise to theories that allow for more consistent deductions of specific hypotheses.

What is the effect of one’s personality on one’s close relationships? In this chapter, we review the literature on this topic, focusing especially on the personality dimensions of self-esteem and the Big 5 traits of neuroticism and agreeableness. We review empirical studies of each of these three traits as predictors of (a) interpersonal processes and (b) relationship outcomes, including relationship satisfaction and dissolution. We also summarize any existing theoretical perspectives on these associations, including the most complete theoretical account offered for the influence of any of these traits on relationships—namely, the Self-Esteem-Infuses-Relationships-through-Trust (SIRT) model. We expect that two core assumptions of the SIRT model would be fundamental to theoretical accounts concerning any personality dimension’s influence on relationships. Specifically, (a) any trait?s influence must exert its influence through a causal chain of mediators, and (b) one of the essential mediators is behaviors between partners. Finally, we also evaluate how complete theoretical accounts concerning neuroticism and agreeableness that are likely to be offered in the future are likely to differ from or be similar to the account for self-esteem offered by the SIRT.

This chapter addresses intimate relationships of Black populations, as well as the sociocultural and economic contexts in which they are embedded. The authors underscore the heterogeneity of Black populations both in, and outside of, the United States. How racial discrimination is experienced, and the impact of that experience, differs across Black populations – underscoring heterogeneity. While some research suggests that racial discrimination contributes to negative relationship dynamics, other work suggests that when some individuals experience racial discrimination their partners engage in supportive behaviors. Despite declines and delays in marriage, many U.S.-born Blacks are still pursuing marital unions and are happily married (Skipper & Taylor, 2021; Skipper et al., 2021). This is likely a function of relational resilience, or even the Black Advantage Vision as many U.S. Black couples adapt and strive in spite of seemingly unsurmountable stressors over which they have little control.

Relationship development and growth have long drawn the interest of relationship scholars. This chapter focuses on the theoretical frameworks that have guided inquiry. We begin by explicating the term relationship development, including different ways researchers have studied it. Traditional theories (e.g., relational dialectics, relationship stage models, social exchange, social penetration, relational turning points) are described, alongside recently developed perspectives on relationship development and growth (e.g., relational turbulence theory, the relationship trajectory framework). The chapter also discusses current research associated with the theories and how this scholarship informs our understanding of the initiation of relationships and how relationships develop over the lifespan. Special attention is paid to the development and maintenance of marginalized relationships. The chapter concludes with suggestions for future research, including the need to assess the ability of current theories to describe development in different relationship contexts (e.g.., friendships, courtship, families) and in different communication contexts (e.g., online, offline).

Chapter 4 covers research on special displays, or secondary placements. These displays signify any type of display that is not the product’s ordinary shelf position. In a grocery store, these are typically the endcaps, also called the gondola ends. But these can also be dump bins or pallets put in the middle of the aisle, or some kind of cardboard stand put anywhere on the store floor. In fashion stores these could be mannequins, torsos, or display tables. The special display is typically found to be the most powerful tool in the retailer’s promotion toolbox. It is also found that in general a special display does not cannibalise the sales from the shelf; the special display rather serves as a more efficient retrieval cue, helping shoppers remember that specific category. If the display is a cross-merchandising display, displaying products that go well together – like food items that together could be used to cook a meal, or a mannequin showing an outfit from trousers to top – it can do an even better job at helping the shopper retrieve a latent want. Special displays are effective because their size and location make them more visible than the typical product display in the shelf.

This chapter examines how experiences of stress became the subject of specific research interest in the very different contexts of work and home during the interwar period. It explores how workers’ nervous conditions were understood, by both employer and employee, and argues that the importance of work in the construction of personal identity and social and economic life contributed to the difficulty of admitting to stress and fostered a stoicism that meant people simply endured whatever mental suffering arose. Personal accounts illustrate contemporary attitudes towards work, duty and responsibility, while early Medical Research Council research reveals employer attitudes focused on productivity and identification of suboptimal workers. It is argued that concerns about domestic neuroticism, seen in Taylor’s suburban neurosis diagnosis and the work of the Pioneer Health Centre, brought to light not only specifically gendered explanations of stress, but also changing conceptions of the home that contributed towards domestic strain.

Aggression in an intimate relationship violates commonly held expectations that a romantic partner will be loving and supportive. Partner aggression erodes the quality of a relationship and can cause people to experience significant psychological distress and pain. This chapter critically examines research on features of aggression in relationships, how partner aggression is regulated and maintained, and interventions and efforts to address partner aggression. We aim to convey the current state of research on partner aggression and suggest new directions for research.

This chapter reviews the literature on responses to wrongdoing in close relationships. We begin by discussing what we know about transgressions as they occur in relationships. We then explore research and theorizing on three related but distinct ways of responding to wrongdoing (forgiveness, unforgiveness, and revenge) that vary in the nature of the response, the research attention they have attracted among those who study relationships, and the extent to which they are viewed as appropriate, desirable, and healthy. We also consider directions for future research and comment on how current methodology and theory can be extended in this area. We ultimately encourage relationship scholars to approach investigation of relational wrongdoing with openness to the possibility that forgiveness may not always and inevitably be the best way forward by exploring when, for whom, and under what circumstances both forgiveness and its less favourably viewed alternatives produce desirable versus undesirable outcomes.

This chapter explores emerging regulatory, ethical, and design frameworks for managing the expanding influence of both digital and chemical mind-altering agents. It reviews current efforts at neuroethics, platform governance, and pharmaceutical policy, highlighting both successes and failures. Key topics include the addictive potential of immersive AI, digital feedback loops, and synthetic neurochemical enhancers. The chapter evaluates international disparities in legal treatment, focusing on how cultural assumptions influence what is considered ’mind-altering’ or harmful. Case studies include data on AI companions, cognitive profiling, and attempts to legislate digital well-being. The concept of ’cognitive sovereignty’ is introduced — the right to autonomy over one’s attention, emotion, and self-perception. In conclusion, the chapter advocates for a post-disciplinary approach combining neuroscience, design ethics, anthropology, and legal studies.

This chapter expands the analysis of altered states to include behavioural addictions — particularly gambling — and explores the psychological and economic mechanisms that drive compulsive risk-seeking. It traces the cultural history of gambling from ancient dice games to digital platforms, arguing that many such practices tap into the same neural reward systems as chemical substances. The concept of ’near-miss’ stimulation, variable reinforcement schedules, and illusion of control are explored in detail. The chapter also interrogates how modern gambling institutions are designed to maximise engagement, often targeting vulnerable populations. Public policy debates on regulation, harm reduction, and the blurry line between entertainment and addiction are introduced. Ultimately, this chapter situates gambling within a broader continuum of mind-altering practices that combine ritual, fantasy, and economic aspiration.

This chapter presents an overview of recent trends and developments in research on close relationships. It is a sequel to the chapters that appeared in earlier editions of this Handbook (Perlman et al., 2018; Perlman & Duck, 2006) and thus reviews the developments in relationships research from 2016 to mid-2023. Drawing on data from a survey of authors of articles published in Personal Relationships and the Journal of Social and Personal Relationships and a bibliometric analysis of these papers, we discuss the scholars who relationship scientists perceive as eminent and who they feel are emerging as influential. We use these data to highlight the major theories, methodological trends, and substantive foci that have been the foundation of relationships research since 2016. Comparison with earlier versions of the chapter reveals stability in the field’s preoccupations but also demonstrates how it has responded to contextual factors within and outside of academia.