Pietraszewski's analysis of “what is a group?” is novel and stimulating. However, the gusto with which he dismissed the existing research as vague was overwrought and counterproductive. Except for an occasional citation with minimal elaboration, he did not engage with the social psychological work he dismisses and he omits several relevant contributions. We particularly found this puzzling because it is not obvious to us that Pietraszewski's theorizing provides any more clarity and specificity than the research that he criticizes.

Social psychologists interested in group dynamics have worked on tightening their conceptual understanding of psychological representation and process by adapting mental models from cognitive science. The concept and category literature was brought to bear on how people represent themselves and others as individuals and as group members (e.g., Brewer, Reference Brewer, Srull and Wyer1988; Fiske & Neuberg, Reference Fiske, Neuberg and Zanna1990) and the formation of stereotypes and prejudice were interpreted through models of attention and memory (e.g., Devine, Reference Devine1989; Greenwald & Banaji, Reference Greenwald and Banaji1995; Hamilton & Gifford, Reference Hamilton and Gifford1976). As cognitive science (and related motivation, affective, and neural sciences) advanced, social psychologists updated their definitions accordingly (e.g., Amodio and Ratner, Reference Amodio and Ratner2011). Although more research is undoubtedly needed, the social psychology of groups is not the straw man that Pietraszewski depicts.

Moreover, the standard that Pietraszewski uses when evaluating the research of others is not the one he uses for himself. He criticizes social psychologists for relying too strongly on intuitions, but his theorizing seems very much based on his own intuitions. Pietraszewski provided no empirical evidence to support his assertions. It is unclear why, for instance, he assumes that perceivers inherently view the behaviors in his primitives as evidence for intergroup behavior instead of a string of dyadic interpersonal behaviors. In Figure 3 he circumvents this ambiguity by labeling some positions in the diagram as ingroup and some as outgroup. However, this solution is as tautological as the container metaphor he chastises. He also uses rhetorical sleight of hand to excuse vagueness in his own theorizing. He limits the scope of his analysis to intergroup conflict when it is convenient for him, although his aims often seem broader. This scope-narrowing for himself is particularly glaring because he criticizes the field as a whole for not being able to account for how groups, in general, are represented. He also frames his ideas as simply working toward a comprehensive theory, which allows him to defer the hard work to future directions. He ignores that sometimes people derogate ingroup members more than outgroup members (e.g., Marques, Yzerbyt, & Leyens, Reference Marques, Yzerbyt and Leyens1988). He leaves vague how people reason about groups when they are not privy to observing behaviors of people over time and how his reasoning applies to representing groups that are not in conflict. He also derides similarity-based definitions of groups, but he seems to rely on perceivers inferring similar fate and goals of allied agents when analyzing the group-constitute roles.

By dismissing social psychology he misses an opportunity to engage with research that is relevant to his research. We offer two examples. First, his interest in understanding the nature of groups from an evolutionary perspective reminded us of Caporael's core configurations model (Reference Caporael1997; Brewer & Caporael, Reference Brewer, Caporael, Schaller, Simpson and Kenrick2006). Caporael's analysis discusses different kinds of groups (dyad, work/family group, deme, and macrodeme), the functions of these groups, and the tasks that each size group facilitates. Group size and the different functions of groups are not taken into account by Pietraszewski and considering these variables in relation to Caporael's research could be useful for thinking about how Pietraszewski's primitives might scale and what other primitives could be considered.

Second, other social psychology research, based on data-driven analyses, has shown that groups can be clustered into five different types: intimacy groups (e.g., families), task-oriented groups (e.g., work team), social categories (e.g., those defined on the basis of gender, race, nationality), loosely associated groups (e.g., individuals employed by the same large technology company), and transitory groups (e.g., people waiting at a particular airport terminal) (Lickel et al., Reference Lickel, Hamilton, Wieczorkowska, Lewis, Sherman and Uhles2000). These groups differ in their perceived entitativity, in the pattern of features used to determine that a collection of people constitute a group, and in how information about the groups are stored in memory. A series of experiments (Sherman, Castelli, & Hamilton, Reference Sherman, Castelli and Hamilton2002) demonstrated that people not only understand these group type distinctions, but they also spontaneously use them in processing and storing information. In addition, Johnson et al. (Reference Johnson, Crawford, Sherman, Rutchick, Hamilton, Ferreira and Petrocelli2006) address the question of function, showing that these different group types serve different human needs or motives (affiliation, achievement, and identity). It is also notable that the way that Pietraszewski talks about ancillary attributes is reminiscent of Hamilton, Sherman, & Lickel's (Reference Hamilton, Sherman, Lickel, Sedikides, Schopler and Insko1998) application of Brunswick's lens model to understand entitativity. For Pietraszewski to achieve his larger aims of creating a grand computational theory about groups he would need to consider many of the issues that have been discussed by these researchers.

From our vantage, Pietraszewski's theorizing does not supplant existing research and is instead on the same theoretical plane. We believe that theoretical integration rather than competition between models of “groupness” is the best path forward. We laude Pietraszewski's call for more theoretical specificity and see it as consistent with recent pleas by mathematical psychologists (e.g., Guest and Martin, Reference Guest and Martin2021) calling for psychologists across all topic areas to more explicitly declare their theoretical premises. We further appreciate how Pietraszewski invokes Marr's levels of understanding to illustrate the complementary ways that an information processing theory of groups should be articulated. Although psychologists interested in social dynamics have found Marr's organization useful (e.g., Cunningham, Zelazo, Packer, & Van Bavel, Reference Cunningham, Zelazo, Packer and Van Bavel2007; Lockwood, Apps, & Chang, Reference Lockwood, Apps and Chang2020; Mitchell, Reference Mitchell2006), the literature on groups (to our knowledge) had not previously taken advantage of this framework. We are optimistic that greater integration across psychology's subdisciplines and adjacent fields coupled with recent efforts to embrace open science, to use more naturalistic experimental paradigms, and to recognize that cognition can be distributed across individuals, will continue to improve definitional specificity and validity in the psychological investigation of group living.