I–C–E Framework: Concepts for Group Dynamics Research in Human-Robot Interaction

The field of human-robot interaction (HRI) has developed over the last 20–30 years [73]. Studies in this field often involve a human participant and the robot, as an interaction partner. Considering potential, ubiquitous deployments of embodied robots and their integration in daily future life, the scenario of one human and one robot interacting with each other in isolation will be unrealistic in most of the deployment scenarios. Robots will be co-workers, servants, maybe even companions, and thus, will be integrated in a social network consisting of more than only one human interaction partner, and possibly more than only one robotic partner.

Research in the field of social psychology investigating human groups shows that group-level processes are fundamentally different from individual-level processes. One of the earliest research in this field was done by Kurt Lewin who is known as the founder of field theory in social sciences [48]. The theory builds upon the assumption that individual behaviour results from personal and environmental factors, and the interaction of both. A group influences an individual’s behaviour due to the individual’s interaction with other members in a social setting. This is what Lewin called “interactionism”. Group phenomena can only be understood when a group as a whole is studied on the group-level and cannot be fully understood by observing individuals, thereby ignoring group influences or social settings [26]. An example of group processes that cannot be explained by individual preconditions is the phenomenon of groupthink which is described as an erroneous process of decision making due to social dynamics in groups. Janis Irvin analyzed failed decision making processes by expert groups, among others the Challenger disaster where security concerns somehow got lost in the decision process which finally led to the tragic decision the spacecraft was ready for flight. His explanation of this erroneous decision making is “a mode of thinking that people engage in when they are deeply involved in a cohesive ingroup, when the members’ strivings for unanimity override their motivation to realistically appraise alternative courses of action” (1982, as cited by [42]). In other words, groupthink appears in groups that are highly cohesive which leads group members to commit mistakes because agreement is set as the highest goal. The example of groupthink shows why research on a group-level is so important. In consideration of findings from group dynamics research and the likely event of robots playing a part in social settings in the near future, research on robots and groups is necessary. Still, groups that interact with robots or robot groups are seldom studied, although the need for a paradigm shift has been acknowledged [29, 44].

Entitativity, meaning the perception of social groups, is seen as a fundamental antecedent of many phenomena studied in social psychology [63]. The term entitativity was coined by Campbell who proposed to apply empirical evidence from visual perception of physical entities to the perception of social groups [13]. Influenced by Gestalt principles such as proximity (elements that are close to each other are grouped together), similarity (elements that are alike are seen as belonging together), common fate (elements moving in the same direction form an entity) and good continuation (elements forming patterns are grouped together), Campbell described the perception of belongingness and their boundaries of social groups as entities. Entitativity is the degree of having the nature of an entity [13]. Still, 40 years later, the concept of entitativity seems to be based upon Campbell’s proposal. In three studies, Lickel et al. [53] examined factors that differentiate groups from one another and those factors’ relation to the perception of the groups’ entitativities. They give the example of an ethnic group and a family that differ in terms of group size, the number of interactions among group members and many other factors (e.g. group size: ethnic group is large, family group is small). In their article, they attempt to find a common framework for studying groups and show that groups are perceived differently concerning their entitativity or “groupness”. Variables such as perceived interaction (e.g. amount and intensity of interactions between group members), common goals (e.g. all members of a sports team want to win a game), common outcomes (e.g. a working team presents their solution for a problem), similarity of group members (e.g., similarity in appearance: same hair color or skin tone, same clothing style, wearing uniforms, speaking the same language) and importance of the group are strongly correlated with entitativity. Moreover, group size, duration (e.g. long-lasting group like family or incidental group such as a group of people waiting for the bus) and permeability (e.g. a family is hard to get into vs. you are easily a new member of the group waiting for the bus) are correlated to a weaker extent with perceived entitativity [53]. They tried to answer the question of when a conglomerate of individuals were actually seen as a group, an entity, and when they were simply seen as individuals. Conducting a cluster analysis on participants’ perceptions of the Gestalt principles mentioned above, they identified four categories of entitativity: intimacy groups, task groups, loose associations and social categories. In their experiments they let participants indicate how they would rate different conglomerates of people from “not at all a group” to “very much a group”. In total, 16 different conglomerates were rated using the VAS. Results showed, that loose associations such as a waiting line at a bank or people at bus stops were seen on the lower end of the concept of “groupness” while intimacy groups such as families and task groups with strong common goals such as sports groups were sorted to the upper end. Medium scale ratings were given to social categories such as “women” and other task groups such as “work teams”.

Ip studied the influence of Gestalt principles on perceived entitativity of groups [39]. In their studies they used cartoon aliens to exemplify different constellations. Different from the previously described study by Lickel et al. [53], here, the focus was on finding out which specific cues led participants to see a group as entitative [39]. Thus, participants were given different information on the cartoon aliens, e.g. a group of aliens that was physically similar or that moved synchronously. They found: similar ratings of entitativity resulted from different information. Furthermore, the authors describe the mediating role of perceived common traits for the perception of entitativity when physical similarity was the cue. In addition, the perception of common goals mediated the relationship between synchronous movement and the rating of entitativity [39]. A rather complex relational model of cues is the result of this research. The main finding, however, is that the extent of entitativity was rather independent of the cue given: the ratings were similarly high or low. These findings are consistent with a theory of the formation of perceived entitativity. The theory postulated that a group can be perceived as entitative resulting from two distinct ways: through a categorical construal and a dynamic construal. Depending upon the information an observer has, he or she base their perception upon either categories or dynamics. Both, perceived similarity of group members (a categorical construal) and perceived interaction (a dynamic construal) were found to be antecedents of entitativity [63]. The reported findings suggest that entitativity does not depend on a single cue or factor, but is rather based upon many cues independently, or a combination of them [69].

In general, the more diverse a group’s members are perceived and the bigger the group is, the less entitative it is perceived [56]. Does this statement hold true in any case? Are diversity and size of a group negatively correlated to entitativity? Rutchick et al. [63] theorize that, on the one hand, an entitative group that is defined by its category is perceived as sharing common traits that are long-lasting. On the other hand, dynamic groups can be diverse and be perceived as entitative as long as they share agency characteristics, for instance, behavioural tendencies.

When reviewing entitativity research, it becomes apparent that entitativity is operationalized by subjective observer ratings and should in consequence be called “perceived entitativity”. In consideration of the fundamental beginnings of conceptualizing entitativity, meaning its origin in Gestalt principles, the observer perspective seems inherent to the concept of entitativity. Furthermore, as an external observer only perceives the group as a whole, the description of groupness is based on the group level, rather than on an individual level. An observer is unable to infer how strongly related the group really is and how strongly related each individual feels towards other members of the group.

Cohesiveness was first described as the willingness to stick together in a group and stems from research by Kurt Lewin and colleagues [20]. Cohesion was later defined as a set of forces that keep members together: attraction and repulsion [20]. In contrast to entitativity, that describes how a collective is perceived as a unified entity, group cohesiveness is described as the actual degree to which a group is unified and coherent [53]. Additionally, cohesion has been named in the context of small groups and named the most important variable of small groups [8]. Still, there is a considerable amount of unclarity around the term. The above mentioned descriptions and definitions of cohesion do not indicate whether cohesion depends on factors on the individual level, such as a member’s attraction to the group, or on the group level, such as the presence of other groups [69].

In 1950, Festinger and his students Schachter and Back studied cohesion of two housing units at MIT [25]. They defined cohesion as “the total field of forces which act on members to remain in the group” (p. 37) and distinguished between attractiveness of the group and group goals. Dion describes this definition as the beginnings of the differentiation of social and task cohesion [20]. From their studies, Festinger et al. [25] concluded that the higher the group’s cohesion, the less deviating behavior was shown. A review of the conceptualization of cohesion from field of forces to a multidimensional construct was done by Dion in 2000 [20]. Dion explains that Festinger and colleagues distinguished between the housing units and subgroups, e.g. closer friendships, and set standards for further group research [20]: there is not only one kind of group, groups have different qualities.

Many studies between the 1940s and 1970s involve factor analyses disentangling individual and group variables (e.g. [18]). With the use of factor analyses, researchers started to view cohesion as a multidimensional concept. An influential model stems from research conducted in the field of sports psychology where group processes play an important role. This model integrated the multidimensional view of cohesion [20]:

Carron [15] developed a model and an instrument to assess cohesion, the group environment questionnaire (GEQ). Carron et al. [14] defined cohesion as a twofold construct: on the individual level and on the group level. The individual level involves a member’s perception and evaluation, e.g. attraction towards the group (see Fig 1). The group level includes factors such as team members’ perceptions of similarity within the group and closeness to the whole group. In a factor analysis, the concept of cohesion with its two levels was further researched and found to consist of two more dimensions besides the individual and group differentiation. The following sub-scales are thus reflected in the GEQ [14]:In the present paper, this twofold level approach is adopted for all concepts and integrated in the below described conceptual framework: group-level and individual-level. Much of the research on cohesion was conducted with groups such as sports teams, therapy groups [69], and in the military [20]. Hence, research on cohesion normally involves well-established groups. This gives a hint on how cohesion is conceptualized in social psychology. In other words, cohesion is described as resulting from group development processes that lead to an “intense” group [26]. How does a group develop cohesion? The classic group development theory by Bruce Tuckman gives an explanation [70]. Group development comprises 5 different stages: Forming (the orientation stage which consists of self-disclosure and information gathering among the newly formed group‘s members), storming (a stage dominated by conflicts and a lack of unity), norming (called the structure stage where the group forms norms, roles and cohesion), performing (performance stage) and adjourning (dissolution stage). Especially, the third stage is of importance for cohesion formation according to Tuckman. Establishing norms and rules form a better unity and the group becomes a more intense experience for its members [26]. However, this unanimity of a group can lead to negative consequences such as groupthink [26]. As explained in the introduction part of this paper, groupthink occurs in groups that are highly cohesive and leads to decision-making processes that can have fatal outcomes (cf. Challenger disaster, [42]) On the contrary, cohesion can have positive effects. Cohesion was found to be positively correlated to performance in real groups (not laboratory groups), in correlational studies (not experimental studies) and in small groups rather than in large groups [58]. Does cohesion cause good performance? Forsyth et al. [27] found out that groups that succeed in a task report to feel more cohesive after their performance. After reviewing studies on the cohesion-performance relationship, Forsyth summarizes the relationship is bidirectional: “Cohesion makes groups more successful, but groups that succeed also become more cohesive” (p. 156, [26]).

In order to understand how humans start to identify with a group (cf. Sect. 4.3) they are or become a member of, we first have to understand how humans categorize themselves into groups (cf. Sect. 4.1) and why they do so (cf. Sect. 4.2). In the following subsections, first of all, the theories of social identity and self-categorization are explained. Thereafter, ingroup identification is described.

Drawing on our faceted review of ingroup identification (I), cohesion (C), and entitativity (E), the purpose of our proposed I–C–E Framework as depicted in Fig. 2 is to integrate the concepts and explain their relationship to each other.

We have carved out on which conceptual level the concept should be located—a group level or an individual level. Moreover, we specify whether the consideration of the concepts entail an inside member perspective or an outside observer perspective. In this regard, entitativity is conceptualized as a group-level variable from an outsider/ observer perspective. Cohesion can either be on the group-level or on an individual-level, but necessarily from an inside member perspective. ingroup identification is conceptualized as an individual level variable and can be measured through an inside member perspective. This encompasses methodological consequences regarding how the concepts can be measured (cf. Sect. 6).

All three concepts are correlated. In the following paragraph, relations among the concepts are further explained.

Our review has shown how important it is to (i) know precisely the concept under consideration and (ii) take into account the levels and perspectives when it comes to measuring group phenomena. As discussed in the previous chapter, study results suggest that there is considerable overlap of the concepts entitativity, cohesion, and ingroup identification. However, as we demonstrated, most of this identified overlap can be ascribed to the lack of precise operationalization of the concepts. Hence, it is important to

The field of social robotics and HRI relies on theories from the social sciences. The I–C–E framework provides a common ground for group (dynamics) research in the field, but we see this only as the beginning. Other concepts on group dynamics can be integrated by using the framework’s differentiation of group and individual level on the one hand, and the differentiation of inside member or outside observer perspective on the other hand.

The previous chapter has demonstrated that although there are measures available to assess the concepts ingroup identification, cohesion, and entitativity, some of these measures should be revised in order to properly operationalize the concepts they shall cover. This is especially true for entitativity and cohesion. Moreover, further methodological development regarding measures is advisable since we have today other possibilities to technically assist data collection. For instance, eye-contact between interactants might be a relevant but until today rather unexplored measure. With wearable eye-trackers it is possible to explore whether eye-contact between group members relates to low or high ingroup identification or perceived cohesiveness.

With regard to methodology, we further face the task to create meaningful interaction paradigms in HRI to study characteristics of groups and their members. For this purpose, we have to identify which small group paradigms from social psychology research can be transferred and maybe adapted. Also, HRI specific scenarios have to be created, since by their nature, multi-agent groups are different from all-human groups. These differences, especially with regard to (social) capabilities of the robotic group members and hence agency perceptions of the robotic agents in comparison to the human agents are giving research on group dynamics a new twist. This latter overarching question finds its reflection on every concept level as the following potential future research questions will show:

Can a multi-agent group (human-robot group) be entitative? We would postulate that this is the case, as long as predictive cues such as similarity and common goals are somehow apparent to the observer. In accordance with Tennent et al. [68], who built a robotic device, MicBot, that shapes human group interaction, but was not designed to look human-like, future research could focus on the mechanisms that influence observers to perceive entitativity. A robotic team member, like the robotic arm in the drawing, might be used to find the outer borders of entitativity. Would a robotic arm and MicBot be perceived as team members? Or is a robot only perceived as a member if it mimicks the human form and/ or human social behavior?

Can a multi-agent group be cohesive? We would hypothesize that, given group members are attracted to the group itself (social cohesion) and committed to the common task (task cohesion), a multi-agent group can be cohesive. The specific circumstances and conditions are to be researched. Fraune et al. [29] have postulated that the cohesion (cohesion according to this framework, although the authors refer to entitativity) can influence the quality of interaction of a human group with a robot.

Can humans identify with robot groups and multi-agent groups? The question of ingroup identification with a group of robots might be the most interesting, as it is not yet understood and researched what might lead humans to identify with a robot (group). In contrast to entitativity and cohesion where some research in the field of HRI has been conducted and predictive cues give plausible hypotheses that multi-agent groups can be entitative and cohesive, ingroup identification with robots is still a very open question. The simple prerequisite of red hair as an ingroup identification factor, as in the example above, is not applicable to robots. Being a very novel constellation, a multi-agent group might generally provide the opportunity for more insights in the psychological processes at hand when groups and social identities are formed. As postulated by Reese et al. [61] and their research on identification with all humanity, will the category of humanity stay the highest order of social abstraction? Or will there emerge an even more abstract level of intentional agents with the sub categories humans and robots?

Will these concepts be applicable to physically embodied robots only? The theoretical background from social psychology on relevant concepts for interacting in human-robot mixed groups generally can also be transferred to other artificially intelligent agents that are virtually embodied or voice-based only as long as these agents are designed to work in groups together with multiple humans. However, prior research has consistently shown that robots and their virtual counterparts can elicit different effects (a review can be found in [52]). In our own prior work, we showed that the embodiment, corporeality and morphology of artificially intelligent systems elicits specific expectations about interaction capabilities of the agents within the human interactants [34, 35] which in turn explain differences in the agents’ evaluations. Hence, it can be expected that although the concepts and the framework can be used with different kinds of embodiments, the empirical results will probably differ between embodiments thereby providing a different empirical basis to build upon when designing agents for group interactions.

As fascinating as human-robot interaction has been all these years, we look ahead to new and possibly even more interesting times when HRI scholars face countless new research paradigms on (social) group dynamics to be discovered as they boldly go where (almost) no one has gone before.