Strong Teams: Not Who, but How
What really makes strong teams successful – and why the answer may surprise every leader
Google wanted to know exactly. Over a period of two years, an internal research team under the project name Aristotle analysed around 180 teams, more than 200 interviews and over 250 potential influencing factors to answer a seemingly simple question: What makes a team successful? The initial hypothesis was obvious – the best combination of skills, experience and personalities should make the difference. The results showed that factors such as individual characteristics and team composition alone did not reliably explain team performance. What mattered most was how team members worked together – particularly psychological safety, dependability, structure and clarity, as well as the meaning of the work.
For leaders who assemble, reorganise or lead teams through change on a daily basis, this is an uncomfortable but liberating insight. Uncomfortable because it shows that a team made up entirely of top performers is no guarantee of success. Liberating because it shifts the focus to something that can actually be shaped: the structure, composition and rules of collaboration. The following findings from several decades of team research show which concrete levers can be used – regardless of whether a team is being newly assembled or an existing team is being further developed.
Team Size: The Underestimated Lever of Leadership
Anyone who leads a team continuously makes decisions about its size – with every replacement hire, every new project and every restructuring. Team research provides concrete guidance on this. Psychologist J. Richard Hackman and his colleague Neil Vidmar found that team member satisfaction was highest with a group size of four to five people; as group size increased, dissatisfaction rose almost linearly. However, this does not allow for a universally applicable optimum of five to ten people in terms of performance, as the relationship depends strongly on the task and team context.
The reason lies in a simple calculation: with each additional person, the number of possible communication connections grows not linearly, but according to the formula n(n−1)/2. A team of five people creates ten such connections; with ten people, there are already 45, while with fifteen people, the number jumps to more than 100. Each additional person therefore means more coordination effort – time that is subsequently unavailable for the actual work. The well-known practical test of Amazon founder Jeff Bezos puts it succinctly: If a team can no longer be fed with two pizzas, it is too large.
How strongly team size actually affects innovation capability has been examined in a broad meta-analysis in the Journal of Applied Psychology, bringing together three decades of team research. The meta-analysis showed that team size alone is not a reliable predictor of innovation. Larger teams can bring additional perspectives and competencies, while at the same time coordination effort increases. Factors more strongly associated with innovation included a shared vision, support for innovation, task orientation and internal communication linked to an atmosphere of psychological safety. For leadership practice, this means that before filling an open position, it is worth asking whether the existing team can already meet the staffing need through clearer goals and better coordination. In times of tight personnel budgets, it pays to optimise the existing team before making a replacement hire.
The Ringelmann Effect: When Effort Becomes Diluted in a Group
In addition to pure coordination effort, there is a second, psychologically deeper reason why larger teams are not automatically more productive: so-called social loafing. This refers to the tendency to show less individual effort in a group than when working alone. The classic study on this is more than one hundred years old. French engineer Max Ringelmann had participants pull on a rope and measured the force they exerted. As group size increased, average individual pulling force decreased; however, the percentage figures frequently cited later should be interpreted with caution, as the historical study does not meet today’s methodological standards.
Two explanations are considered particularly plausible: diffusion of responsibility, because an individual’s contribution becomes less visible within the group, and the coordination effort itself, which consumes energy. Two very concrete levers emerge from this for everyday leadership. First: clearly defined sub-tasks with explicit responsibility instead of vague shared goals. Second: regular individual feedback rather than exclusively collective team evaluations. Both measures require little additional time, but they make each individual aware that their contribution is noticed – regardless of how many others work in the same team.
The Iceberg of Diversity: What Is Often Overlooked When Building Teams
A helpful image for the question of the right team composition is the iceberg. Only the tip is visible, around ten percent of its volume. The much larger part lies below the water’s surface and cannot be directly observed. Applied to teams, research distinguishes between surface-level diversity, meaning observable characteristics such as age, gender, background or educational qualification, and deep-level diversity, meaning personality, values, beliefs and motives that only become apparent over the course of collaboration. A widely recognised study examined how the influence of both levels changes over time. At the beginning of collaboration, visible characteristics dominate the image team members form of one another. The longer a team works together, however, the more these characteristics recede into the background – and the more personality, values and actual beliefs gain importance.
For leaders conducting an interview or putting together a project team, this means: Those who strongly focus on visible characteristics at first impression take into account factors whose importance can change over the course of collaboration. Asking targeted questions about values, preferred ways of working and motives during the interview provides an early first impression of this level.
How strongly different forms of diversity affect innovation capability is shown by a frequently cited study of 199 US banks. Higher levels of education and, above all, functional diversity were associated with greater innovation capability. By contrast, no comparably robust relationships were found for differences in age and organisational tenure. For the composition of a project team, this means: A deliberate mix of different professional backgrounds – for example, sales, technology and finance within the same working group – can provide an important foundation for innovation.
Personality: Why the Weakest Link Carries More Weight Than the Average
With deep-level diversity, personality moves to the centre. A well-established model for this is the Big Five model, with the dimensions openness to experience, conscientiousness, extraversion, agreeableness and emotional stability. A broad meta-analysis summarised which personality characteristics of a team are actually related to its performance. Conscientiousness and agreeableness were among the particularly relevant characteristics: teams with higher average levels of these traits tended to show better performance. However, the strength of these relationships depends on the particular team and task.
A second finding from the same line of research that is particularly relevant to personnel selection concerns not the average, but the minimum within a team – the so-called weakest-link dynamic. Particularly in highly interdependent teams, a single person with very low conscientiousness can impair the reliability of collaboration – for example, when tasks are not completed consistently, agreements are not kept or deadlines are missed. For hiring and promotion decisions, this leads to a simple but often neglected question: Does this person meet the necessary minimum level of reliability and willingness to cooperate – regardless of how impressive their CV may otherwise be? A technically brilliant but chronically unreliable team member often causes more damage than their technical contribution can compensate for.
It is also interesting how extraversion and openness affect team creativity: Both characteristics can be associated with creative performance in a team, especially when the team also believes in its own ability to solve the particular problem. For leaders, this means a double lever: Bringing extroverted, open people into the team is not enough on its own. It is equally important to delegate genuine decision-making authority so that a team can develop this confidence in its own abilities in the first place – an aspect that is particularly often underestimated when promoting someone into their first leadership role.
Too Much Talent: When Top Performers Get in Each Other’s Way
A common misconception is: The more talented people there are in a team, the better the result. A widely recognised study examined precisely this phenomenon in professional sport and found that above a certain proportion of top performers, team performance partially declined again. This was particularly observable in sports with a high degree of coordination, such as basketball or football. The authors explain this in terms of increased status and leadership conflicts: When several people simultaneously want to lead and push through their own ideas, internal competition increases at the expense of collaboration. A later study using a larger dataset from the NBA, by contrast, found no corresponding negative effect of additional talent and therefore questioned the general applicability of the original finding. The research evidence is therefore not conclusive.
For the composition of project or leadership teams, the practical core message nevertheless remains: Talent alone does not make a strong team. Those who reflexively bring together the most renowned specialists available for an important initiative, without clearly separating roles and decision-making processes in advance, risk precisely the kind of status competition that can paralyse top teams. A clear role and decision-making structure can help limit potential status and coordination conflicts.
For leaders who, over the course of their careers, increasingly take on responsibility for leading teams of specialists, it is therefore worth taking a deliberate look at the type of task: The more closely the individual contributions within the team need to interlock, the more important a clear distribution of roles among top performers becomes. For tasks that can be divided more strongly into independent individual contributions – such as parallel client mandates in consulting – a high proportion of top performers is much less likely to have a negative effect.
Faultlines: The Invisible Fracture Line Within the Team
The term originally comes from geology: A faultline is a fracture in rock, a crack beneath the surface that remains invisible until the rock is put under pressure. In team research, the term describes an analogous phenomenon: When several differences between team members overlap along the same line, potential subgroups can emerge that, under certain conditions, have a divisive effect. The problem is not diversity itself, but the overlap of several differences along the same dividing line.
In everyday leadership, this often appears along very ordinary lines: between office and home-office employees, between long-standing and newly added team members, or between two departments that have been merged for a joint project. As soon as location, organisational tenure and working style overlap along the same line, a faultline can emerge. Research shows that such faultlines do not automatically have negative consequences. They become problematic especially when the potential subgroups are actually activated. A recent meta-analysis of 168 studies shows that activated faultlines are associated, among other things, with more conflict, less information exchange and lower team performance.
The good news: Leaders can reduce the risk of problematic faultlines. These include, among other things: first, overarching common goals that carry more weight than affiliation with one’s own subgroup; second, mixed and rotating collaboration that repeatedly creates new constellations across the presumed dividing line, for example through deliberately mixed pairs working on sub-tasks; and third, psychological safety, which allows all team members to contribute regardless of their subgroup. This brings us to the concept already mentioned, which the Google study referred to at the beginning identified as the most important of all success factors.
Psychological Safety: The Common Denominator of All Findings
The concept of psychological safety was already coined and empirically studied in the late 1990s by Harvard researcher Amy Edmondson. In a study of 51 work teams in a manufacturing company, the findings showed: Psychological safety – the shared belief that it is possible to take interpersonal risks within a team without being humiliated or punished for doing so – was closely linked to team learning behaviour, and this learning behaviour in turn mediated the relationship between psychological safety and actual team performance. Almost two decades later, the Google research team also identified psychological safety as the most important of the factors examined for team effectiveness. Reliability, structure and clarity, meaning in work and perceived contribution to the greater whole also played an important role.
This finding fits seamlessly with all the findings described above and at the same time explains how they work together. A team can choose its size as intelligently as possible – if members do not express concerns and differing perspectives, important information remains unused. Psychological safety can therefore help ensure that different perspectives, experiences and professional competencies actually feed into collaboration.
For everyday leadership, this leads to a concrete, immediately applicable catalogue of behaviours. Addressing one’s own mistakes and uncertainties openly instead of pretending to be confident signals to the team that fallibility is allowed. Actively inviting critical questions instead of waiting only for agreement shifts the norm from silent consent towards genuine exchange. And responding to a dissenting opinion with curiosity rather than defensiveness often determines within seconds whether a person will dare to say something again next time. These measures do not necessarily require an additional budget or reorganisation, but above all consistent behaviour from the leader in everyday practice.
Three Levers for Leadership Practice
The topics described above give rise to three concrete questions for leadership practice. First, team size: Is the team deliberately sized according to what the task requires, or has its size grown historically? Second, diversity: When making the next hire, are values, working style and the necessary minimum level of reliability also considered, rather than just professional competence? Third, psychological safety: Do all members of the team actually feel confident enough to ask uncomfortable questions – and what does the leader do to ensure that this remains the case or becomes possible in the first place?
Those who answer these three questions seriously turn their attention to some of the well-researched factors of successful teamwork. Because while many leaders focus their energy on attracting the smartest people to their team, research as a complete picture shows: The greater lever often lies not in who sits on the team, but in how the team works together – an insight that can be translated directly into leadership practice, entirely without additional budget or new personnel decisions.
For high performers who are on their way towards increasingly greater leadership responsibility, this represents an underestimated opportunity for differentiation. Professional excellence alone is becoming less of a differentiator at senior management levels – most candidates for leadership positions already bring it with them. Those who additionally understand how team size, diversity, personality mix and psychological safety interact, and can translate this knowledge into their own leadership practice, can use this knowledge strategically in their leadership practice.
About the Author
Dominique Giger is a leadership expert, speaker, and coach with over 18 years of international experience in transformation management, change management, and strategic corporate development.
She holds a master’s degree in computer science from ETH Zurich and combines scientific insights from neuroscience, psychology, and leadership with practical management experience from international corporations.
Her focus is on sustainable high performance: the connection between mental strength, healthy performance, and modern leadership.
As a speaker and author, she explores the topics of mindset, transformation, resilience, and leadership in an increasingly complex work environment.
In her podcast “Y-SHIFT: The Next-Level Mindset & Transformation Podcast,” she regularly shares insights into the world of modern psychology, neuroscience, and leadership development.
Learn more about this topic in Episode 39 of her podcast: How Do You Build a Successful Team? The Science Behind Team Size, Diversity, and Collaboration.
YouTube: https://youtu.be/ZwuL9tRrEbQ
Apple Podcasts: https://podcasts.apple.com/us/podcast/folge-39-wie-baut-man-ein-erfolgreiches-team-auf-die/id1801021329?i=1000786525379
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