Leader individual differences, situational parameters, and leadership outcomes: A comprehensive review and integration

Abstract

In this article, we provide a wide-ranging review of recent research on leader individual differences. The review focuses specifically on the explosion of such research in the last decade. The first purpose of this review is to summarize and integrate various conceptual frameworks describing how leader attributes influence leader emergence and leader effectiveness. The second purpose is to provide a comprehensive review of empirical research on this relationship. Also, most prior reviews primarily examined leader personality traits; this review includes a broader array of leader attributes, including cognitive capacities, personality, motives and values, social skills, and knowledge and expertise. The final broad purpose of this paper is to review and integrate situational and contextual parameters into our conceptual framing of leader individual differences. Few, if any, prior reviews have systematically accounted for the critical role of such parameters in cuing, activating, or delimiting the effects of particular leader attributes. We do so in this article.

Introduction

The theme of individual differences that contribute to leadership is the longest-standing research topic in the science of leadership. Zaccaro, LaPort, and Jose (2013) identified reviews of this theme dating back to the 1920s and '30s. In that time span, the degree to which scientists focused high and sustained attention on leader traits and other attributes waxed and waned (Zaccaro, Kemp, & Bader, 2004) until the late 1980s and early '90s, when meta-analyses (e.g., Lord, De Vader, & Alliger, 1986), methodological advances (e.g., Kenny & Zaccaro, 1983), and new conceptual frameworks (e.g., House and Howell, 1992, Mumford, 1986) propelled the topic to a higher level of prominence. Indeed, reflecting this shift, Leadership Quarterly published three special issues on leadership and individual differences in 1991 and 1992 (e.g., Fleishman, Zaccaro, & Mumford, 1991).

Over the last 30 years, several increasingly complex models have emerged that describe how individual differences may be related to leadership outcomes. For example, Fleishman, Mumford et al. (1991) offered a taxonomy of functional leadership behavior that provided the basis for the specification of antecedent leader traits and attributes. Mumford, Zaccaro, Harding, Jacobs, and Fleishman (2000) used the fundamental arguments of this taxonomy to propose a process model of leader attributes and behaviors. Zaccaro et al. (2004) expanded this approach to argue for integrated patterns of leader attributes predicting leadership outcomes. Both models specified distal, more stable traits as antecedents to leader characteristics that were more mutable, and in turn likely proximal predictors of leadership outcomes. Others have described how followers develop schemas and cognitive networks of leader attributes used in making judgments about potential leaders (Dinh and Lord, 2012, Lord, 1985, Lord and Maher, 1993, Shondrick et al., 2010). Researchers have also examined how leader traits can have both positive (bright) and deleterious (dark) effects on leadership outcomes (Judge, Piccolo, & Kosalka, 2009). An alternative framework, reflecting the “too-much-of-a-good thing” phenomenon (Pearce & Aguinis, 2013), has argued that moderate levels of leader traits predict outcomes more strongly than high and low levels (Kaiser and Hogan, 2011, Kaiser et al., 2015). These contributions have answered earlier calls for conceptual advancements (Lord & Hall, 1992) and brought vibrancy to the literature on leader individual differences.

This increase in conceptual sophistication has been matched by a proliferation of empirical summaries and meta-analyses. Between 1986 and 2010, meta-analyses of leader individual differences were published focusing on personality and motives (Bono and Judge, 2004, DeRue et al., 2011, Judge et al., 2002, Lord et al., 1986, Stewart and Roth, 2007), intelligence (Judge, Colbert, & Ilies, 2004), sex differences (Eagly et al., 2003, Eagly and Johnson, 1990, Eagly and Karau, 1991, Eagly et al., 1995, Eagly et al., 1992), and social capacities (Day et al., 2002, Harms and Crede, 2010). These meta-analyses demonstrated significant corrected correlations between particular leader individual differences and various leadership outcomes. Also, in the period of 1986–2010, these meta-analyses were matched by several summaries of the literature that affirmed the importance of leader traits and attributes for leadership (Hogan and Kaiser, 2005, House and Howell, 1992, Judge et al., 2009, Kirkpatrick and Locke, 1991, Zaccaro et al., 2004).

A recent special issue of Leadership Quarterly recognized this growing body of work, and noted the increased complexity of models linking leader individual differences to leadership outcomes (Antonakis, Day, & Schyns, 2012). That special issue contained articles that integrated multistage and information processing perspectives of leader attributes (Dinh & Lord, 2012), offered a pattern or profile approach to both followers' leader perceptions and leader/follower composition (Foti et al., 2012, Richards and Hackett, 2012), and provided a methodological focus on traits, as measured by self- versus other-ratings (Colbert, Judge, Choi, & Wang, 2012). These articles offered different perspectives that reflected more multifaceted and multivariate combinations of leader individual differences; that is, they went beyond prior approaches that tended to focus on univariate relationships with leadership outcomes (Zaccaro, 2012). The promise of this research led Antonakis et al. (2012) to declare that research on leader individual differences was “at the cusp of a renaissance” (p. 643).

Since that time, there has indeed been an exponential surge in research on leader individual differences. Xu et al. (2014) counted 45 articles on leader traits that were published in Leadership Quarterly alone in the 4-year span of 2011–2014, one more than the total number of such articles published in the two decades between 1991 and 2010. For this article, we surveyed issues of Leadership Quarterly published in 2015 and 2016, and found an additional 36 articles (including 13 that focused on leader gender). This represents a more than 6-fold increase in the annual mean number of such articles published in just the last 7 years in comparison to the previous 20 years in Leadership Quarterly!

Given this explosive growth, we believe there is a need for a comprehensive and integrated review of recent research on leader individual differences. Leadership scholars have complained about a lack of coherence in the leadership literature (Avolio, 2007, DeRue et al., 2011, Tuncdogan et al., 2017). The rapid proliferation of empirical studies in the past decade has increased this sense of fragmentation (Tuncdogan et al., 2017). Studies have examined a range of individual differences, specified a range of relationships among a variety of personal variables and outcomes, and offered a range of explanatory mechanisms for these relationships. This scattering propagation of different explanatory mechanisms without an integrating framework is perhaps the most chaotic element in the leader individual differences literature. There is a need, then, for a comprehensive conceptual framework that can offer clarity on this growing base of empirical studies by linking their findings through integrated explanatory processes.

A number of literature reviews have appeared through the history of leadership research in order to provide summaries and integrations of the field (see summary by Zaccaro et al., 2013). More recent reviews, both before and during the current period of growth, have varied considerably in the range of individual differences they have covered. For example, the review by Judge and Long (2012) was limited to personality traits, with their effects on leadership outcomes mediated by leadership styles (and motivation to lead). An earlier review by Judge et al. (2009) also focused primarily on personality traits, but included intelligence and leader skills and abilities, albeit with little discussion of the latter. Antonakis (2011) also focused primarily on personality, motives, and intelligence, but questioned the utility of such social capacities as emotional intelligence and self-monitoring. Tuncdogan et al. (2017) continued this primary focus on personality and intelligence. Their model, like the ones by Judge et al. (2009) and Antonakis (2011), specified genes as critical exogenous predictors of leader traits.

DeRue et al. (2011) offered a model that specified a wider range of leader individual differences under categories of demographics, task competence, and interpersonal competence. The influences of these sets of attributes on leadership effectiveness were mediated by leadership style, as well as followers' attribution and identification processes. Mumford et al. (2000) defined cognitive abilities, personality, and motives as causal precursors of more specific leader problem-solving abilities and skills, which in turn predicted leadership performance. Models offered by Zaccaro et al. (2004) and Zaccaro, Dubrow, and Kolze (2018) also specified additional categories of leader attributes within process models. These contributions point to key leader individual differences beyond personality and intelligence.

Recent reviews have also modeled various antecedents and relationships among leader individual differences. Antonakis et al. (2012) noted the proliferation and contributions of process models that attempted to arrange leader individual differences into sets of characteristics that predicted (a) distal leader traits, (b) proximal leader attributes, (c) leadership styles and leadership behavior, (d) follower behavior, and (e) overall leader effectiveness. In some models, the effects of traits on effectiveness have been mediated by leadership styles and/or behaviors (Antonakis et al., 2012, Judge and Long, 2012, Tuncdogan et al., 2017); others have added follower processes, along with behavioral styles, as mediators of trait influences on outcomes (DeRue et al., 2011, Dinh and Lord, 2012). In still others, these relationships have been mediated by more specific leader knowledge, skills, and abilities (KSAs), which in turn have influenced outcomes (Antonakis, 2011, Judge et al., 2009, Zaccaro et al., 2004, Zaccaro et al., 2018). This proliferation of meditational models suggests a need for an integrating framework of leadership effectiveness that places particular individual differences and behavioral styles at different stages of a process model, with a clear conceptual rationale, supported by prior empirical findings, for the various placements.

Several of these models have also specified moderators of the relationships between leader individual differences and outcomes, with the most common being the leader's context or situation. The role of situation has been a conundrum in past research on leader individual differences. Most process models of leader individual differences have posited a role for situations. However, this role has often been left obtuse or treated in fairly narrow ways. Some models have argued that situational variables determine which leader traits predict leadership effectiveness in different contexts, thus acting as a moderator of trait influences (Ayman and Lauritsen, 2018, Fiedler, 1967). Others have argued that the situational performance requirements determine which leadership behaviors will be most functional for effective leadership, thus acting as a direct determinant of leadership behavior (Hersey and Blanchard, 1969, Mumford et al., 2000, Vroom and Jago, 1988, Zaccaro et al., 2004, Zaccaro et al., 2018). Still other models have argued that the situational or environment moderators may influence the degree to which leadership behaviors influence particular leadership outcomes (Ayman and Lauritsen, 2018, Dinh and Lord, 2012, Judge et al., 2009).

Some researchers have argued for more integrated person-situation perspectives. Trait activation models have posited that situational factors cue particular leader individual differences, both in terms of providing a context for trait expression (Tett and Burnett, 2003, Tett and Guterman, 2000) and influencing follower information processing (Dinh & Lord, 2012). Other approaches have argued that leader individual differences determine perceptions of the environment and subsequent reactions to situational characteristics. In these approaches, situational influences have been embodied in the leader's perceptions of the situation and selection of behavioral responses to those perceptions (Dinh and Lord, 2012, Hooijberg, 1996, Zaccaro et al., 1991).

These different models and perspectives suggest significant complexity and ambiguity regarding the role of situational characteristics in the development, influence, and expression of leader attributes. Most of the aforementioned models of leader individual differences and leadership outcomes have treated the influences of the leader's context in vague or nonspecific terms. Researchers have therefore called for greater clarity regarding the situational characteristics or dimensions that may influence leadership behavior, either directly or by moderating the influences of leader traits (Dinh and Lord, 2012, Hoffman and Lord, 2013, Zaccaro, 2012).

This integrative review is intended to address some of the issues we have noted with prior models, summaries, and reviews of the leader individual difference literature. In this review, we strive to achieve several goals. First, we offer a conceptual framework that integrates several other previous models of leader individual differences. This framework reflects core assumptions across these models, and adds additional ones. As we noted earlier, theories and explanatory mechanisms behind proposed relationships in prior models have been generally fragmented, incomplete, or absent. In our framework, we integrate and expand upon prior explanations to better inform the placement of attributes in phases of a process model of leader individual differences.

Second, our model reflects a multivariate perspective that emphasizes both additive and pattern combinations of leader individual differences (Zaccaro et al., 2013, Zaccaro et al., 2018). Most of the exponential increase in leader individual difference research over the last 6 years has focused on more complex relationships than those between single predictors and outcomes. In this review, we provide a comprehensive and updated summary of the empirical evidence for several multivariate models of individual differences, including variable, pattern, and process models of leader attributes. Our intent is to extract from this review well-grounded conclusions about the relationships among combinations of leader individual differences and leadership outcomes.

The final goal of this review, and the one that may provide the most substantive contribution to the extant leadership literature, is to systematically integrate the role of the leadership situation into a model of leader individual differences. Personality theorists have provided more advanced conceptual frameworks on how the integration of personality and situational characteristics influences subsequent behavioral expression (e.g., Dalal et al., 2015, Fleeson and Jayawickreme, 2015, Rauthmann et al., 2014, Tett and Guterman, 2000). With few exceptions (e.g., De Hoogh et al., 2005, Dinh and Lord, 2012, Ng et al., 2008, Phaneuf et al., 2016), these advancements have not made their way into the mainstream of research on leader individual differences and contexts. In this review, we examine the role of individual differences in the leader's responses to situational characteristics. We also provide examples of task and social situational parameters that afford the expression of particular leader attributes. We intend that these elements of our review provide new ways to consider leadership situations in future research.