I suggest that we should distinguish between weak and strong group-level traits. It is the latter that are especially problematic for developing models of cultural evolution. Using Campbell's notion of vicarious selection mechanisms, I argue that these mechanisms become intertwined with other group-level traits resulting in selection-transmission thickets that are obstacles to modeling cultural evolution.

Smaldino's target article draws on and seeks to add to a literature that has partially rejected orthodox, gene-centric evolutionary theory. However, orthodox theory has much to say about group-level traits. The target article does not reference or refute these views, and provides no explicit arguments for this narrow approach. In this commentary we: (i) give two examples of topics that the target article might and probably should have discussed (cultural epidemiology and the psychology of individual differences); and (ii) argue that the orthodox approach has much more to say about the emergence of group-level traits than the target article recognises, or gives credit for.

Following Smaldino's definition, we claim that language is also an emergent group-level trait, and propose two facets (human groups tend to organize in a way to efficiently trigger language and linguistic interactions can render formation of certain social organization) to verify this statement, both of which also provide a general framework to address the future work about group-level traits.

Although religions, as Smaldino demonstrates, provide informative examples of culturally evolved group-level traits, they are more accurately analyzed as complex adaptive systems than as norm-enforcing institutions. An adaptive systems approach to religion not only avoids various shortcomings of institutional approaches, but also offers additional explanatory advantages regarding the cultural evolution of group-level traits that emerge from religion.

The target article argues that whole groups can act as interactors in an evolutionary process. We believe that Smaldino's discussion would be advanced by a more thorough analysis of the appropriate replicators and lineages for this model. We show that cultural evolution is necessarily a separate process from cultural group selection, and we also illustrate that the two processes may influence each other as demonstrated by an agent-based model of communicating food-processing skills.

We extend Smaldino's approach to collaboration and social organization in cultural evolution to include cognition. By showing how recent work on emergent group-level cognition can be incorporated within Smaldino's framework, we extend that framework's scope to encompass collaborative memory, decision making, and intelligent action. We argue that beneficial effects arise only in certain forms of cognitive interdependence, in surprisingly fragile conditions.

Group-level traits (GLTs) clarify the necessity of cultural multilevel selection theory. We propose a revised definition of the GLT concept. We also highlight the need to better understand the interplay between the dimensions of cooperation and coordination in the ontogeny of GLTs.

Whenever selection operates at a given level of a multitier hierarchy, units at that level should become the object of functional analysis, and units at lower levels should be studied as proximate mechanisms. This intuition already exists for the study of genes in individuals, when individuals are the unit of selection. It is only beginning to be applied for the study of individuals in groups, when groups are the unit of selection. Smaldino's target article is an important step in this direction with an emphasis on human cultural evolution, but the same algorithm applies to all multilevel evolutionary processes.

Smaldino makes a solid contribution to the literature on the evolution of human social organization by pointing out that group-level-traits (GLTs) often emerge from the interactions of group members in such a way that their effects are not easily partitioned into individual selection. However, we argue that he too readily dismisses institutional analysis as a tool for understanding these traits.

Most commentators supported the thesis of the target article, though there were also those who were less fully persuaded. I will begin with a response to the most critical commentaries. First, I will justify an evolutionary perspective that includes group organization and nongenetic inheritance. Next, I will discuss the concept of emergence. Following that, I will transition to an exploration of ideas and concerns brought up by some of the more supportive commentators. This will include a discussion of different types of groups; the psychology of group-level traits; the uses and limitations of an institutional perspective; the link between transmission, adaptation, and selection; current and future methodologies; and the variety of fields that may benefit from a group-level traits perspective.

Disputes between those holding differing political views are ubiquitous and deep-seated, and they often follow common, recognizable lines. The supporters of tradition and stability, sometimes referred to as conservatives, do battle with the supporters of innovation and reform, sometimes referred to as liberals. Understanding the correlates of those distinct political orientations is probably a prerequisite for managing political disputes, which are a source of social conflict that can lead to frustration and even bloodshed. A rapidly growing body of empirical evidence documents a multitude of ways in which liberals and conservatives differ from each other in purviews of life with little direct connection to politics, from tastes in art to desire for closure and from disgust sensitivity to the tendency to pursue new information, but the central theme of the differences is a matter of debate. In this article, we argue that one organizing element of the many differences between liberals and conservatives is the nature of their physiological and psychological responses to features of the environment that are negative. Compared with liberals, conservatives tend to register greater physiological responses to such stimuli and also to devote more psychological resources to them. Operating from this point of departure, we suggest approaches for refining understanding of the broad relationship between political views and response to the negative. We conclude with a discussion of normative implications, stressing that identifying differences across ideological groups is not tantamount to declaring one ideology superior to another.

Negativity bias may underlie the development of political ideologies, but liberals and conservatives are likely to respond to threats similarly. We review evidence from research on intolerance, motivated reasoning, and basic psychological threats that suggest liberals and conservatives are more similar than different when confronting threatening groups, situations, and information.

This commentary advances the hypothesis that differences between liberal and conservative orientations noted in the target article are emotional in nature and caused by differences in attachment security: Conservatives are more vigilant to negative features of the environment because of a general sense of insecurity, whereas liberals are relatively more secure.

There is an extensive literature on the negativity bias, including its conceptualization, measurement, temporal stability (individual differences), and neural and genetic associations. Hibbing et al. posit that the difference across individuals in the negativity bias is a key factor in determining political predisposition. The measures and paradigms developed in this literature provide a means of testing this hypothesis.

The authors connect conservatism with aversion to negativity via the tendentious use of the language of threats to characterize conservatism, but not liberalism. Their reliance upon an objective conception of the negative ignores the fact that much of the disagreement between liberals and conservatives is over whether or not one and the same state of affairs is negative or positive.

Hibbing and colleagues argue that political attitudes may be rooted in individual differences in negativity bias. Here, we highlight the complex, conditional nature of the relationship between negativity bias and ideology by arguing that the political impact of negativity bias should vary as a function of (1) issue domain and (2) political engagement.

At odds with Hibbing et al., we argue that political ideology is best explained by at least two dimensions linked to economic and social ideology. In addition, Hibbing et al's claim that conservatism is grounded in a heightened sensitivity to negative outcomes, something closely tied to the personality trait of neuroticism, does not fit with the established personality correlates of political ideology. Conscientiousness and a lack of openness to experience are linked to conservatism but there is no established connection to neuroticism.

Hibbing and colleagues argue convincingly that liberals and conservatives differ in reactivity to (negative) stimuli. Yet their analysis sidesteps evidence that cognitive ability differs as a function of ideology. Cognitive abilities, like cognitive preferences (e.g., structure needs), shape whether stimuli are psychologically threatening (prompting avoidance) or offer opportunity (prompting approach). Incorporation of these findings is critical despite any socially “delicate” implications.

Hibbing et al.'s article isolates a plausible psychological factor contributing to differences in political orientation. However, there are two potential difficulties. Both the nature of negativity and the liberal–conservative opposition are ambiguous. A possible way of treating these problems enhances the theoretical framework through fuller reference to emotion systems and categories of triggers for those systems.

We address two questions regarding the relationship between political ideology and responses to threatening or aversive stimuli. The first concerns the reason for the connection between disgust and specific political and moral attitudes; the second concerns the observation that some responses to threat (i.e., neuroticism/anxiety) are associated with a more left-wing political orientation.