Credit: Ana Bigio


Behavioral Science

MIT Sloan study finds task complexity impacts group efficiency


Two heads are better than one for more complex tasks

CAMBRIDGE, Mass., Sept. 21, 2021 – Is the saying true that two heads are better than one? Or do too many cooks in the kitchen spoil the broth? A new study by MIT Sloan School of Management Assistant Professor sheds light on this age-old debate. He found that the answer depends on the complexity of the task.

“The question of whether – and under what conditions – groups of interacting problem solvers outperform autonomous individuals can have real consequences. In a winner-take-all market, it can mean the difference between making profits and going out of business,” says Almaatouq. “Past research shows that it is advantageous to assign tasks to individuals or groups depending on conditions, but what are those conditions? That is what we looked at it in this study.”

Using his virtual lab platform, Empirica, Almaatouq conducted an online, large-scale experiment to test the hypothesis that the answer depends on the characteristics of the task. More specifically, he looked at the complexity of a task, meaning the number of components in a task and the nature of the interdependencies between them.

Almaatouq found that teams are far more efficient than individuals when it comes to complex tasks. However, individuals are more efficient at simple tasks. “We find that groups are as fast as the fastest individual and more efficient than the most efficient individual when the task is complex, but not when the task is simple,” he says.

This is likely because there are costs associated with teams, such as time spent talking to each other, social dynamics in which some members put forth more effort than others, and a tendency toward herd mentality, notes Almaatouq. However, there are also benefits of teamwork, where members can do parallel processing to divide and conquer different parts of a task.

The study revealed that while the cost of being on a team is fixed, the benefits of teams increase as the complexity of a task increases. If the task is simple, then the cost of teamwork is greater than the benefit. If the task is of higher complexity, then the benefits of a team surpass the costs.

“A challenge is that we lack precise language to compare tasks that are seemingly different from each other in terms of complexity. It’s hard to quantify and measure those differences. In this study, we used a task with known computational complexity that we can translate into human complexity. This allowed us to vary the complexity of the tasks in the experiment in an objective way to see how individuals and groups performed,” he explains.

The bottom line for managers, according to Almaatouq, is that the allocation of work should depend on the complexity of the task at hand and the way performance is evaluated. For example, if managers want to find a workable solution to a problem in the least amount of time, they should ask a group to solve the problem when the problem is complex – and ask independent problem solvers when it is simple.

Almaatouq is co-author of “Task complexity moderates group synergy” with Duncan Watts of the University of Pennsylvania, MIT Sloan PhD student Mohammed Alsobay, and Ming Yin of Purdue University.

About the MIT Sloan School of Management

The MIT Sloan School of Management is where smart, independent leaders come together to solve problems, create new organizations, and improve the world. Learn more at