Abstract
 More than half a century of cross-cultural research has demonstrated group-level differences in psychological and behavioral phenomena, from values to attention to neural responses. However, cultures are not static, with several specific changes documented for cultural products, practices, and values. How and why do societies change? Here we juxtapose theory and insights from cultural evolution and social ecology. Evolutionary approaches enable an understanding of the how of cultural change, suggesting transmission mechanisms by which the contents of culture may change. Ecological approaches provide insights into the why of cultural change: They identify specific environmental pressures, which evoke shifts in psychology and thereby enable greater precision in predictions of specific cultural changes based on changes in ecological conditions. Complementary insights from the ecological and cultural evolutionary approaches can jointly clarify the process by which cultures change. We end by discussing the relevance of cultural change research for the contemporary societal shifts and by highlighting several critical challenges and future directions for the emerging field of cross-temporal research on culture and psychology

Key Concepts for Research on Cultural Change: Culture, Time, Ecology, and Cultural Evolution
Before we begin our review of the literature on cultural change, it is important to reflect on several key concepts often used when discussing this topic. First, it appears nec-essary to provide a working definition of culture. Though there are myriad definitions of culture (e.g., Bruner, 1990; D’Andrade, 1984; Dimaggio, 1997; Grossmann & Na, 2014; Shweder, 1991), we believe most share certain common-alities including an emphasis on shared knowledge and practices. For our purposes, we define culture as a set of ideas, beliefs, norms, and behaviors shared by or com-mon to a group inhabiting a geographic location (see Table 1).Human societies vary in a range of psychological and behavioral tendencies. Scholars have observed cross-cultural variations in processes ranging from visual illu-sions to reasoning about the causes of others behavior (Henrich, Heine, & Norenzayan, 2010). Further, a grow-ing body of research has shown such differences exist not only in downstream behavior and self-report but also in neural responses (Han et al., 2013; Kitayama & Uskul, 2011). Thus, any understanding of the mind that does not take culture into account is almost certain to be incomplete (Henrich et al., 2010; Markus & Kitayama, 1991; Nisbett, Peng, Choi, & Norenzayan, 2001; Wang, 2016).Second, it is important to consider the concept of time in such research. Time is an abstract concept and often functions as a proxy for other processes. To understand this claim, consider several metaphors. On an individual time scale, factors such as “age” can reflect biological maturation, sociological shifts, adjustment of psychologi-cal functioning, or a combination of these factors (Wohlwill, 1970). Void of such processes, the notion of “aging” appears to be meaningless. Similarly, change at the level of an organization can reflect a change in the organization’s revenues, shifts in organizational structure, or the process through which certain outputs have been achieved (Pettigrew, Woodman, & Cameron, 2001).Though macrocultural processes are not identical to those found on the level of an individual (Na et al., 2010) or a small group (Pettigrew et al., 2001), the notion of change on the cultural scale likely also concerns a multi-tude of factors, including evolution of ideas, refinement of practices, reactions to shifts in social-ecological affor-dances, and so on. As we discuss below, unpacking tem-poral changes in culture requires a rigorous evaluation of theoretical and empirical links between shifts in particu-lar cultural psychological variables and shifts in theorized ecological and evolutionary factors believed to underpin these changes