Summary Informal hierarchies are a common and important feature of many groups, yet we know little about the antecedent conditions that determine the strength of such hierarchies. Building on theory that has depicted hierarchy as a mechanism for reducing uncertainty and creating structure, we posit that informal hierarchies emerge most strongly in situations that are ambiguous, ill‐defined, and unstructured. Three independent studies confirm this notion, demonstrating that groups develop particularly strong informal hierarchies in situations characterized by both a lack of strong formal leadership and high task complexity. These findings support the theoretical notion that formal and informal hierarchies are closely related, but only under conditions of high task complexity in which the structuring functions of hierarchies are most crucial.

Although there is growing evidence that strong informal influence hierarchies can enhance teams core task performance, recent theorising suggests that such informal hierarchies may, at the same time, stifle team creativity. The current study draws from the Motivated Information Processing in Groups (MIP-G) model to empirically examine this latter notion. Moreover, we build on functional leadership theories to propose that the link between informal hierarchy strength and team creativity hinges on a formal team leaders empowering leadership. Using a sample of 56 organisational work teams comprising 304 individuals from a wide range of industries, we found that stronger informal influence hierarchies related negatively with team creativity when the formal leader exhibited little empowering behaviour. When the formal leader acted in more empowering ways, by contrast, this negative relationship was dampened. These findings provide new knowledge on the role of informal influence hierarchies for team creativity and advance our understanding of how informal hierarchical relations and formal leadership processes can jointly shape important team outcomes.

History is replete with examples of powerful individuals who do not get along. A famous example of a conflict between two powerholders is the attempted coup by former chairperson and co-founder of Apple Inc., Steve Jobs, in 1985, against Apple's chief executive officer (CEO) of that time, John Sculley. There are, however, also numerous examples of powerholders who do seem to care for each other. A few years later, this same Steve Jobs, for instance, was very empathic towards Heidi Roizen, who, at that time, was the head of software company T/Make. When she told him, during a business call, that her father passed away, Steve Jobs responded: "Then why are you working? You need to go home. I'll be right over."When he arrived at her house, he sat with her for hours and talked to her about her loss (Guglielmo, 2012). These examples illustrate that high-power individuals may express empathy and compassion for other powerholders, but at times can find themselves caught up in power struggles as well. A question that these examples raise is under which conditions powerholders are compassionate and caring towards each other, and under which conditions they will compete.Although abundant research has examined the interpersonal consequences of power (defined as asymmetric control over valued resources; Magee & Galinsky, 2008), this work cannot answer the question raised above. We present a systematic review of the literature on power and its interpersonal consequences, which confirms that most studies examining the interpersonal outcomes

Chapter 1 General introduction Chapter 2 On the origins of informal hierarchy: The interactive role of formal leadership and task complexity Chapter 3 Informal hierarchy and team performance: The moderating role of performance alignment and dominance alignment Chapter 4 Informal hierarchy and team creativity: The moderating role of empowering leadership Chapter 5 General discussion References Samenvatting

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