Building on the Big History framework, this chapter proposes that humanity is entering ’Threshold 9’, marked by the convergence of chemical, digital, and symbolic technologies that actively reshape consciousness. It theorises this as an inflection point where ancient drives toward transcendence are recoded through AI, genetic editing, and neuroenhancement. Through speculative but evidence-informed projections, the chapter imagines future societies in which identity, memory, and meaning are co-produced by intelligent systems. Drawing on theories of symbolic entropy, recursive myth, and experiential design, it frames this shift as both an opportunity and a risk — potentially enabling new collective mythologies or deepening crises of coherence and purpose. Threshold 9 represents not a destination but a volatile transitional space demanding new ethical frameworks and cognitive literacy.

Relationship satisfaction has major implications on individuals’ health and subjective well-being, and prominent theories in relationship research have assigned relationship satisfaction an important role. In this Handbook chapter, we first introduce conceptual perspectives on relationship satisfaction, showing that relationship satisfaction is a characteristic of both the individual and the relationship. We then provide an overview of the measurement of relationship satisfaction and discuss common affordances in its assessment. Next, we report empirical evidence on how relationship satisfaction evolves over time, showing that relationship satisfaction changes both normatively and depending on the eventual outcome of the relationship. We then report how relationship satisfaction is associated with different relationship-specific facets, such as perceptions, emotion regulations strategies, and communication styles. To conclude, we discuss a series of unresolved issues in the area of relationship satisfaction research and propose an agenda for future research, such as the usage of modern technologies.

In this culminating chapter, the focus turns to how individuals and societies seek existential meaning in the midst of altered states and cognitive transformation. It examines how spiritual movements, digital subcultures, and philosophical reorientations emerge in response to technological and pharmacological shifts in consciousness. Concepts such as post-secular spirituality, AI mysticism, and techno-shamanism are explored alongside crises of identity, loneliness, and collective memory. Drawing from Viktor Frankl’s existential therapy, narrative psychology, and religious studies, the chapter suggests that the future of meaning-making will require not only critical thinking but symbolic creativity and adaptive ritual. The chapter concludes with a call for integrating ancient modes of reflection with new tools of imagination, proposing a “hybrid literacy” that prepares the mind for the unpredictable and the sublime.

In the present chapter, the authors offer a social exchange theory analysis of processes within intraracial versus interracial relationships. After commenting upon “the rise in intermarriage” (particularly within the United States during the past 50 years), the authors draw upon Levinger’s (1980) Acquaintance-Buildup-Continuation-Deterioration-Ending (ABCDE) model regarding stages of relationship development, highlighting several quantitative studies that examine social exchange processes at each transition or turning point between stages of intraracial and (especially) interracial relationships. Furthermore, the authors address implications of certain interdependence processes for the stability of intraracial and interracial relationships, as well as gaps in the evidence that is available concerning turning points within both types of relationships. Subsequently, the authors identify particular studies that serve as points of departure for suggestions about methodological changes and theoretical additions in future research on intraracial and interracial relationships. Finally, the authors provide examples of still-unanswered questions within the literature on interracial relationships in particular.

The Epilogue provides a reflective distillation of the book’s major claims and anticipatory warnings. It revisits the central idea that the human species is entering a new epoch of cognitive modulation — one that combines the ancient allure of psychoactive substances with the unprecedented reach of digital simulation. It affirms that while such tools offer extraordinary opportunities for creativity, healing, and connection, they also pose significant risks to autonomy, mental integrity, and collective meaning-making. The epilogue emphasises the urgency of ethical design, regulatory foresight, and public education to manage this dual-edged transformation. It concludes with a speculative yet grounded vision: that the next phase of human evolution may depend less on biology and more on how we symbolically navigate our internal and external realities. The final call is for conscious engagement — with our histories, technologies, and altered states — to ensure our adaptations remain humane and meaningful.

Chapter 9 covers the remaining aspects of the visual atmospherics – colours and signage. Colours are often said to comprise three dimensions: hue, brightness contrast, and saturation. The dimension that has been studied the most is hue. Hue is often described as on a scale from warm colours (red) to cool colours (blue). Research has shown that warmer colours tend to take over the visual scene and force their way into the s consciousness of shoppers. A red colour therefore makes shoppers more aroused or even confused and may interfere with the shoppers' ability to notice other stimuli. A store with too many red objects would overload the senses of the shoppers, and therefore it makes sense to instead work with brightness contrast. The eye's ability to detect brightness contrast primarily resides in the rods in the retina, while the cones primarily are responsible for colour vision. Research has shown that independent of hue, a contrast in the brightness level can create an even stronger visual pop-out effect. Regarding signage, it is found that a sign’s primary task is to attract attention. The attention-grabbing aspect is often more important than the communication. The optimal way to write prices is covered in Chapter 13.

Chapter 8 is the first of two chapters on the visual aspects of store atmospherics. In Chapter 8, the primary focus is on the store’s layout. In Chapter 9, the focus is more on colour and signage. A major reason for having two chapters on visual atmospherics is that vision is the most powerful of the human senses. As much as 83% of the sensory input comes from the eyes. The other four senses only contribute 17% of the sensory input jointly. The store layout is discussed as the perhaps most important aspect of the atmospherics tools since it provides the ‘framework’ for the product displays. With a traditional grid layout, research shows that only a few per cent of the shoppers notice any given product, and less than 0.3% of the total range is seen by the average shopper. With the help of the ‘PLEND’ model, various techniques supported by empirical evidence show how the store’s appearance can be improved.

Relationship dissolution, or a breakup, is a common event rife with emotional and psychological consequences, and as such has increasingly become the subject of academic inquiry. Through an interdisciplinary approach encompassing empirical studies, theoretical models, and real-world implications, this chapter aims to offer a multifaceted understanding of breakup. To start, we will focus on defining breakups, considering that they are concepualized through various lenses: as a distressing life event, as a calculated decision, as a gradual process, and as an outcome metric for evaluating other relational constructs. Next, we will describe the most robust predictors of breakup, including characteristics of the partners, about the structure of the relationship, and about how the partners interact. We will next detail the process by which relationships end, how former partners cope with breakup, and what predicts post-breakup outcomes. Collectively, this chapter provides a sweeping review of the science surrounding relationship dissolution.

Chapter 14 covers omnichannel customer journeys. Research has found that the initial digital disruption that occurred as e-commerce started has now settled so that most retailers are working in several different sales channels. It has further been found that even within the same category, customer journeys can be retail specific. The effort to understand the customer journey is called customer mapping. The most generic omnichannel customer journey is webrooming; that is, customer start the purchase journey online by scrolling a social media feed and possibly searching online before fulfilling the purchase in a physical store. The various contacts customers have with the brand are called touchpoints, and it has been shown that different touchpoints serve different purposes. Also, online shopping is a visual process. However, there is a large difference with regards to the visual processes between offline and online shopping. The difference is that in the physical store, the shopper is browsing while walking around the store. Online browsing is done by clicking on links or by typing in a search field. Since the design of the physical store – with its displays, signage, and planograms – is focused on capturing the shopper’s attention, this step can be disregarded in online shopping. Many times, this means that the way products are displayed must be flipped online as compared to offline.

Given that relationship satisfaction is ultimately a cognitive phenomenon, social cognition likely plays a critical role in determining the extent to which intimates are satisfied with their relationships. This chapter begins with a theoretical description of the cognitive processes that determine relationship satisfaction. Following from this framework, the second section reviews work suggesting there are various benefits to thinking positively about one’s relationship. Nevertheless, the third section highlights work suggesting there are important limits to these benefits, such that they depend on qualities of the two partners, their relationship, and the broader context in which that relationship is embedded. The fourth section then introduces the possibility that distinguishing between controlled and more automatic forms of social cognition may offer insights into why such limits exist. The final section concludes by suggesting various directions for future research that may offer insights into how both controlled and automatic thinking shape relationship development.

This integrative chapter highlights the interdisciplinary implications of the book’s core arguments. It synthesises the historical, neuroscientific, cultural, and ethical perspectives covered in earlier chapters, showing how they converge around a central theme: the human impulse to reshape consciousness through external means. The summary identifies key throughlines such as the neurochemical basis of thrill-seeking, the symbolic encoding of drug use, the commodification of altered states, and the rise of digital simulation as a new frontier of mind alteration. It stresses the importance of cross-disciplinary collaboration in addressing emerging challenges — including addiction, mental health, identity fragmentation, and regulatory vacuums. The chapter proposes that future research and policy must account for the hybrid nature of cognitive environments, shaped by both chemical inputs and algorithmic systems. Ultimately, it reaffirms the need to develop new cultural literacies and ethical frameworks suited to the complexities of the digital-chemical age.

Relationships are influenced by how and where they begin. This chapter focuses on the initiation of romantic and nonromantic relationships (e.g., friendships), including those initiated online. We discuss what types of people are selected as friends and romantic partners as well as the role of context in initial social interaction. First, we first explore the influence of geographic and virtual proximity in relationship initiation. Then, we offer homophily and predicted outcome value theories to understand why some people are more socially attractive than others, and why context influences social attraction. Next, we introduce social exchange and partner preference theories to explain why people are sexually and romantically attracted to others. We examine the similarities and differences between online dating and in-person romantic relationship initiation. Finally, we examine the conversational factors – both verbal and nonverbal – leading to attraction. We also discuss specific partner compatibility – that is, what makes two people "click."

In this chapter, we provide an overview of modern methodological approaches to relationship science that is both practical and accessible. We start with a “status report” on the field, outlining three popular methodological trends. First, we discuss the application of machine learning techniques, specifically random forests, to the field of relationships science. Second, we elaborate on the importance of multimodal data, describing studies incorporating physiological, neurological, and linguistic measures. Third, we briefly discuss nonstandard dyadic designs, such as the round-robin design and network analysis, which enable the examination of multiple dyads within larger groups. Throughout these sections, we provide recommendations for scholars who wish to implement these methods in future work. Next, we provide a description of two analytical approaches used frequently in dyadic data analysis – structural equation modeling (SEM) and multilevel modeling (MLM) – and discuss the strengths and weaknesses of these approaches. We also present a brief discussion of differences between statistical software programs and suggestions for when to use each.

In the current chapter, we review the research on close relationships done via the methodologies of neuroscience – in short relationship neuroscience (RN). Much of the research we review focuses on attachment (child–parent or romantic) and sexuality. Nevertheless, we aim to cover RN broadly defined. We start by framing our topic and providing a few working definitions. We then cover the various relational (attachment, interdependence) and neuroscience (social baseline theory, and the Functional Neuroanatomical Model of Human Attachment) theories, methodologies (MRI, ERPs, and genetics), and types of relationships (familial relations, romantic, friendships, sexual relations, etc.) used or covered in this subfield. We explore both positive and negative aspects of close relationships. Finally, we reflect on the bidirectional link and contributions between relationship science and neuroscience and suggest potential implications for mental and physical health and policymaking. We also outline some remaining issues and future directions for RN.