As a highly consequential biological trait, a memory “bottleneck” cannot escape selection pressures. It must therefore co-evolve with other cognitive mechanisms rather than act as an independent constraint. Recent theory and an implemented model of language acquisition suggest that a limit on working memory may evolve to help learning. Furthermore, it need not hamper the use of language for communication.

Both the Now-or-Never bottleneck and the chunking mechanisms hypothesized to cope with it are more variable than Christiansen & Chater (C&C) suggest. These constructs are, therefore, too weak to support C&C's claims for the nature of language. Key aspects of the hierarchical nature of language instead arise from the nature of sequencing of subgoals during utterance planning in language production.

We identify three “working edges” for fruitful elaboration of the Chunk-and-Pass proposal: (a) accounting for the earliest phases of language acquisition, (b) explaining diversity in the stability and plasticity of different representational types, and (c) propelling investigation of action processing.

Christiansen & Chater (C&C) ignore the many linguistic universals that cannot be reduced to processing or cognitive constraints, some of which we present. Their claim that grammar is merely acquired language processing skill cannot account for such universals. Their claim that all other universal properties are historically and culturally based is a nonsequitur about language evolution, lacking data.

I focus on two challenges that processing-based theories of language must confront: the need to explain why language has the particular properties that it does, and the need to explain why processing pressures are manifested in the particular way that they are. I discuss these matters with reference to two illustrative phenomena: proximity effects in word order and a constraint on contraction.

Rapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Christiansen & Chater (C&C) propose that learning language is learning to process language. However, we believe that the general-purpose prediction mechanism they propose is insufficient to account for many phenomena in language acquisition. We argue from theoretical considerations and empirical evidence that many acquisition tasks are model-based, and that different acquisition tasks require different, specialized models.

I agree with the existence, and importance, of the “Now-or-Never” bottleneck. However, there is a far simpler and more parsimonious solution to it. This solution is predictive processing, and the failure to view the solution that this provides fundamentally boils down to viewing prediction as one aspect of cognition, rather than as its central principle.

If human language must be squeezed through a narrow cognitive bottleneck, what are the implications for language processing, acquisition, change, and structure? In our target article, we suggested that the implications are far-reaching and form the basis of an integrated account of many apparently unconnected aspects of language and language processing, as well as suggesting revision of many existing theoretical accounts. With some exceptions, commentators were generally supportive both of the existence of the bottleneck and its potential implications. Many commentators suggested additional theoretical and linguistic nuances and extensions, links with prior work, and relevant computational and neuroscientific considerations; some argued for related but distinct viewpoints; a few, though, felt traditional perspectives were being abandoned too readily. Our response attempts to build on the many suggestions raised by the commentators and to engage constructively with challenges to our approach.

Ultrasociality refers to the social organization of a few species, including humans and some social insects, having a complex division of labor, city-states, and an almost exclusive dependence on agriculture for subsistence. We argue that the driving forces in the evolution of these ultrasocial societies were economic. With the agricultural transition, species could directly produce their own food and this was such a competitive advantage that those species now dominate the planet. Once underway, this transition was propelled by the selection of within-species groups that could best capture the advantages of (1) actively managing the inputs to food production, (2) a more complex division of labor, and (3) increasing returns to larger scale and larger group size. Together these factors reoriented productive life and radically altered the structure of these societies. Once agriculture began, populations expanded as these economic drivers opened up new opportunities for the exploitation of resources and the active management of inputs to food production. With intensified group-level competition, larger populations and intensive resource exploitation became competitive advantages, and the “social conquest of Earth” was underway. Ultrasocial species came to dominate the earth's ecosystems. Ultrasociality also brought a loss of autonomy for individuals within the group. We argue that exploring the common causes and consequences of ultrasociality in humans and the social insects that adopted agriculture can provide fruitful insights into the evolution of complex human society.

Gowdy & Krall's target article complements our recent theorizing on group behavior. In our comment, we elucidate complementary aspects of the two theories and highlight the importance of differentiation of selves for human groups to reap the benefits of ultrasociality. We propose that achieving optimal group outcomes depends on the differentiation of individual selves.

The parallels between the agricultural successes of ultrasocial insects and those of humans are interesting and potentially important. There are a number of important caveats, however, including the relative complexities of insect reproduction, their more rigidly determined altricial patterns of social behaviour, the roles of post-reproductive group members, and differences in the known factors involved in ultrasocietal collapse.

Drawing lessons regarding the consequences of ultrasociality in ants and humans depends crucially on recognizing differences as well as similarities in the way that species are social. We focus on Gowdy & Krall's use of the concept of autonomy to explicate essential differences in the ways in which ants and humans are social.

Human hunter-gatherers share a suite of traits with social insects, which demonstrates convergent social evolution of these taxa prior to agriculture. Humans differ from social insects in that their divisions of labor are more competitive than cooperative. Resulting higher within-group competition in humans has been alleviated by religion and culturally imposed monogamy, both of which also find parallels among social insects.

Ultrasociality, as expressed in agricultural, monetary, and fossil fuel economies, has spurred exponential growth in population and in resource use that now threaten civilization. These threats take the form of prisoner's dilemmas. Avoiding collapse requires more cooperative economic organization that must be informed by knowledge of human behavior and cultural evolution. The evolution of a cooperative information economy is one possibility.

Gowdy & Krall provide an interesting discussion of evolutionary origins and consequences of ultrasociality. However, some of their statements concerning various features of ant and human social behavior do not adequately reflect present knowledge about the discussed issues, which include, among others, polyethism, cultural information transfer, within-group conflicts and resistance in ant societies, and reproductive division of labor in humans.

Gowdy & Krall (G&K) provide an interesting discussion of evolutionary origins and consequences of ultrasociality, an advanced form of social behavior that evolved independently in both social insects and humans. Their reflections are thought-provoking, but some statements concerning various features of ant and human social behavior do not reflect adequately the present knowledge about the discussed issues.

Experimental studies of group selection show that higher levels of selection act on indirect genetic effects, making the response to group and community selection qualitatively different from that of individual selection. This suggests that multilevel selection plays a key role in the evolution of supersocial societies. Experiments showing the effectiveness of community selection indicate that we should consider the possibility that selection among communities may be important in the evolution of supersocial species.

Agriculture represented a major transition in human evolution, but the appearance of ultrasociality must have included previous steps. We argue that ultrasociality would not have suddenly emerged with agriculture, but rather developed from pre-existing cognitive and social mechanisms. Discussions must include necessary depth about the historical origins of human ultrasociality, and agriculture's aftereffects on large-scale social organization.

Complementary to Gowdy & Krall's comparison between ants and humans, I use economy scaling laws to discuss the similarity and difference between them quantitatively. I hypothesize that individual variations in society result in higher energetic efficiency in larger groups, and that the difference in the sustainability between these species originates from the driving forces of growth with different scaling powers.

We present arguments that the analogy between humans and social insects is coincidental, rather than based upon real similarities. In their claims, Gowdy & Krall largely omit the role of institutions in the formation of complex societies, warfare, and regulation. They also offer no strong explanation for the expansion of agriculture despite its early detrimental effects except the “mistake hypothesis” (cf. Diamond 1987).