Evolutionary Psychology in a Nutshell

Darwin's (1909) theory of evolution posits that if a population displays variation in a given trait, and if offspring can inherit those traits from their parents, then the variants of a trait that improve survival or reproduction in a given environment will increase in frequency from one generation to the next. Variants that hindered survival or reproduction will diminish over time, as they are transmitted to offspring at lower rates relative to their more productive counterparts. An inherited characteristic that, within the time period in which it evolves, improves an individual's ability to survive and reproduce compared with an alternative variation of the trait is referred to as an adaptation. However, the process of natural selection can also produce by-products. By-products can be thought of as the consequence of adaptive traits that serve no function in their own right (e.g., calcium evolved as the material for bones because of its structural advantages, but the fact that it causes bones to be white is a by-product of calcium's chemical structure).

Although an evolutionary framework is commonly applied to explain anatomical or physiological traits in a species, it is of no less importance in understanding how the brains of humans and nonhuman animals developed to process information and generate behavioral strategies. Utilizing the definition offered by Confer and her colleagues, the psychological mechanisms that are generated by natural selection can be understood as, “information-processing circuits that take in delimited units of information and transform that information into functional output designed to solve a particular adaptive problem” (2010, p. 111). These inputs can be thought of as social or environmental signals and the outputs are emotional or behavioral responses to those signals. The mechanism itself can be understood as the neural/physiological pathway that defines the nature of the relationship between the two.

There are two main levels at which evolutionary approaches can be applied to understand psychological phenomena. The first considers the ultimate function of a behavior or cognitive ability—why the psychological trait exists—based on the fitness benefits it is thought to confer on its possessor. The second approach looks at proximate physiological mechanisms that cause it to occur—how the trait actually functions to provide a benefit. Although generally considered complementary, proximate levels of analysis can have important implications for comparative studies, as behaviors that appear alike and offer similar fitness benefits may be governed by different cognitive mechanisms across species. Now that we have outlined the logic of the evolutionary approach, we can examine how it has been applied to study leadership in nonhuman animals.

Evolutionary Perspectives on Leadership in Nonhuman Animals

From a fitness perspective, there are many benefits to grouping including decreased risk of predation, increased foraging success, communal defense of resources, or more accurate migration. However, such benefits may only be achieved if individuals are able to maintain some degree of cohesion, either through physical proximity or through signaling at a distance. Even then, any attempt to remain together as a group (especially over longer distances) will require individuals to engage in some degree of coordination in the activities they pursue. Put simply, individuals in the group cannot engage in activities that are so divergent as to compromise cohesion. However, in forfeiting their optimal action to comply with the group, an individual pays a fitness cost referred to by Conradt and Roper as a consensus cost (2003). These consensus costs are important to evolutionary theories of leadership because they present a fitness paradox. It is in the best interest of any given member of a group to move the group toward their preferred activity (avoiding the consensus cost), but if all members pursue their own interests, the group risks fragmentation and the grouping benefits are lost. Thus, if groups are to remain intact, some members must get their way, whereas others must follow. Here, we see the first and most simplistic way leadership is conceptualized in animal groups, as those behaviors that determine the type, timing, direction, or duration of group activities (e.g., Dyer, Johansson, Helbing, Couzin, & Krause, 2009; Guttal & Couzin, 2011). To understand this more fully, let us consider a concrete example.

One of the most common fitness benefits of grouping seen across taxa, and considered to be the origins of grouping in primates (van Schaik, 1983), is the reduction in the risk of predation (Alexander, 1974). This can be due to either increased vigilance or decreased probability of any given individual being the target of attack. Particularly in the latter instance, maintaining proximity to neighbors is necessary for the fitness gains to be achieved. When considering a proximate explanation, staying near others in the group can be understood as an increased fear response to states of isolation (Bergvall, Schäpers, Kjellander, & Weiss, 2011). At some point, however, the consensus cost associated with remaining near others may become too high for an individual (e.g., when an individual deer needs water but the herd is foraging). In these instances, needs such as thirst or hunger may outweigh fear of isolation and the individual will break with the group. If other members are not themselves in a high state of need (are not thirsty or too hungry), the drive to maintain proximity may result in following the departing individual. By the nature of this relationship, any individual with a higher energy need than other members, or simply a lower fear response to isolation (sometimes termed boldness), may emerge as a “leader” (at least for a time). This increased need may result from many characteristics including physical traits such as larger body size (King, Johnson, & Van Vugt, 2009). Several authors have used this argument to explain why more consistent leader–follower roles are established in stable social groups where size often correlates with dominance (e.g., King & Cowlishaw, 2009).

Interestingly, decision rules that involve maintaining proximity with conspecifics can produce leadership in groups that have only local knowledge (individuals can only see the activities of their neighbors and not necessarily the activity of the “leader”). Ian Couzin and colleagues have demonstrated the remarkable ability of a few “knowledgeable” fish to lead entire schools of “ignorant” fish to resources, simply because those individuals who did not know the location of the resource stayed close to their neighbors and the information percolated from the “leaders” to the rest of the group (Couzin, Krause, Franks, & Levin, 2005).

At this point, one might wonder how this type of leadership is relevant for humans. At the most basic level, Dyer and his colleagues demonstrated that human groups could exhibit similar leadership and followership behaviors to those discussed above (Dyer et al., 2009). In his work, Dyer showed how a group of naive individuals could be lead out of a novel room by a few people who knew the location of exits, without the need for verbal communication. In doing so, Dyer highlighted how a person's physical position within a group can impact the level of influence they have over others. Now consider a company where individuals may only interact with a subset of their coworkers. Individuals who are optimally located in this colleague network (perhaps those with the most connections) may have the ability to influence how others think and feel about their job more so than individuals with fewer ties, regardless of their formal position. To a biologist, this type of influence may be interpreted as a form of leadership.

Some authors (e.g., Guastello, 2009) have argued that for the purposes of evolutionary discussion, decision rules associated with staying or leaving a group should not be characterized as an example of an evolved leader–follower relationship. In part, this objection stems from the fact that the mechanism of influence (maintaining proximity) is unrelated to the decision being pursued (followers are not considering the choice of the leader). In this sense, leadership would be viewed as a by-product of grouping behavior rather than an adaptive solution to problems of coordination. Such arguments are valuable to the extent that they remind researchers that phenotypically similar actions, such as one individual displaying the same behavior as a conspecific at different points in time, may have different proximate explanations and thus there may be a need for more precise terminology than “leadership” to avoid confusion. In the section that follows, we expand on the different types of cognitive mechanisms capable of producing leader–follower dynamics and how unique selection pressures can result in the development of more complex leader–follower relationships.

It is worth noting here that despite the propensity for evolutionary psychologists to discuss adaptations independently of one another, cognitive mechanisms should not necessarily be viewed as isolated modules in the brain. While there is some evidence that certain brain regions, as well as subclasses of neurons, serve specific functions (e.g., areas involved in language, and facial neurons associated with individual recognition in mammals; see Sheehan & Tibbetts, 2011), most psychological adaptations draw on multiple cognitive components, including regions of the brain associated with perception and memory. Additionally, these mechanisms do not operate in a vacuum, but rather build and interact in complex ways to produce adaptive behaviors (Buss, 2008; see Confer et al., 2010).

As bottom-up environmental factors such as predation and resource availability drive animals to aggregate, new selection pressures can emerge and influence how individuals cope with, and take advantage of, their relative proximity (Van Schaik, 1983). The type of problem a species is faced with can therefore alter the mechanisms through which leadership operates (Van Vugt, 2006). For example, one potential challenge to living near conspecifics is that it may be difficult for an animal to hide its movements toward, or discovery of, food (e.g., Ratcliffe & Hofstede, 2005). These “cues” are not evolved mechanisms for communication between the “finder” and those around him, but rather a by-product of living in close proximity that can result in a leader–follower conflict. In these instances, followers may be thought of as “social parasites” and their choice to follow may actually run counter to the interests of the “leader” (Sumpter, 2010). However, in some cases, individuals can actually develop specific adaptations for detecting when followership will be most advantageous. Starlings, for example, tend to make decisions about leaving or staying in a food patch based on the observed success of conspecifics (e.g., Templeton & Giraldeau, 1996). Such instances would be an example of an evolved capacity for followership. The models used to represent trade-offs between gaining information from others as opposed to searching for oneself are known as producer-scrounger models, and they represent a rich theoretical literature on leader–follower dynamics, including how strategies may be adapted to environmental changes (Sumpter, 2010).

The presence of conspecifics does not always represent a challenge to resource acquisition for leaders. Under certain circumstances, they may actually be of benefit, resulting in an individual's active recruitment of others when food is discovered. In cliff swallows, for example, there is evidence that group members are recruited to swarms of insects because the increased numbers helps the birds track their prey (Brown, Brown, & Shaffer, 1991). This type of behavior is often referred to as signaling. Signaling can be understood as “an act or structure that alters the behavior of another organism, which evolved because of that effect, and which is effective because the receiver's response has also evolved” (Maynard Smith & Harper, 2005; cited in Sumpter, 2010 p. 58). Such abilities to sense and interpret cues and signals represent mechanisms that evolved to facilitate the follower side of leadership dynamics. It is possible that the prototypes discussed in attribution theories of social psychology serve a similar purpose—helping people find “good” leaders that will be advantageous to follow.

Evolutionary Perspectives on Leadership in Humans

While all of these examples represent relationships of influence in which individuals are “led” toward a resource, the leader–follower dynamic is governed by different evolved processes shaped by each species' unique evolutionary history (Buss, 2005). While much of the logic outlined in the section above on nonhuman animals may therefore shed light on human leadership, there are also likely to be evolutionary causes and consequences of leadership and followership behavior that are unique to our own lineage. Identifying the unique cognitive adaptations that may have impacted our species social relations is an important and growing aspect of current research on evolutionary leadership in humans. Some scholars, most notably Gil-White and his colleagues, have proposed that specific adaptations for social learning have been integral in shaping our species' leadership dynamics (Henrich & Gil-White, 2001). In their model of “prestige,” Henrich and Gil-White argue that with the advent of the human cognitive capacity for cultural transmission, fitness benefits could be attained by preferentially learning from the most skilled individuals. Unlike more primitive forms of copying found in other species (Boyd & Richerson, 1985), which could be utilized at a distance, social learning in humans was facilitated by increased access to informed or skilled individuals. This created a selection pressure for behaviors aimed at gaining greater access to high performing individuals, including deference. There is some evidence for this effect in hunter–gatherer societies in which outright leaders are rare, but certain individuals wield influence confined to their own areas of expertise (Van Vugt, Hogan, & Kaiser, 2008). Interestingly, trading deference for productivity is not unique to humans. In macaques (Ventura, Majolo, Koyama, Hardie, & Schino, 2006), high performing foragers are preferentially groomed, even if they are low ranking in the dominance hierarchy.

The unique nature of human phylogenetic history may raise questions about the value of studying leadership in other taxa. The complex nature of human cognition and social structure can make isolating the processes that contribute to any behavior incredibly difficult. Cross-species comparative research can control for noise and mediating variables, as well as simplify environmental factors. But there is no guarantee that understanding the ultimate and proximate explanations for leadership in other species will translate directly into understanding leader–follower dynamics in humans, given our own unique evolutionary history (Buss, 2005; Van Vugt, Hogan, & Kaiser, 2008). However, it does offer the promise of identifying fundamental, underlying patterns that transcend species boundaries. When general terms such as “leadership” are abandoned, and the focus is confined to specific behaviors, several interesting patterns may emerge.

In conclusion, current institutionalized leadership roles—while prevalent in today's society—may not reflect the types of behaviors associated with leader–follower dynamics in human evolutionary history and, by extension, the psychological mechanisms that evolved to facilitate them. At times, institutionalized structures may conflict with people's evolved relational standards of fairness, integrity, or competence. The term commonly employed to discuss this phenomenon is mismatch theory (Van Vugt et al., 2008; King et al., 2009). For example, most organization heads are not selected by subordinates (Sessa, Kaiser, Taylor, & Campbell, 1998), yet higher levels of leadership continuity have been found when groups could elect their own leader. This suggests that distinctions need to be drawn between cultural stereotypes of leadership and perceptions of leadership that may be more innate. An evolutionary approach offers new ways to account for this variation.