In 1913, French engineer Maximilien Ringelmann conducted an experiment that predicted the problem of almost any large team long before the emergence of modern occupational psychology. He asked people to pull a rope—first individually, then in groups—and measured the total force. It would be logical to expect a group of eight people to pull conventionally eight times harder than one person. In practice, they do not: the more people there are in a group, the less effort each individual participant exerts on average.
There are two reasons, and they are distinct. The first is coordination loss: it is physically more difficult to synchronize the efforts of eight people than of one, and part of the energy is lost simply on coordinating movements. The second is motivation loss, which is more interesting for organizations: when an individual's contribution cannot be accurately measured against the group's overall result, people experience a decreased subjective feeling that their personal effort matters. This is not about laziness in a moral sense—it is a rational, albeit unconscious, response to diffused responsibility.
In companies, this manifests in committees, working groups, and large cross-functional projects. A team of ten people is formed for an important initiative—and intuitively it seems that this should speed things up. In reality, the opposite happens: the more people are formally responsible for the result, the fewer specific individuals feel personal responsibility for ensuring that the result actually happens.
The practical takeaway is not that large teams are unnecessary—sometimes a task objectively requires many hands. The takeaway is that group size alone does not generate productivity, but often consumes it—unless the effect is compensated for intentionally.
What helps:
making individual contributions visible rather than dissolving them in the group's overall result;
breaking large initiatives into smaller zones of personal responsibility with a clear owner;
keeping working groups at a truly workable size—usually significantly smaller than what one intuitively wants to gather "for the importance of the matter."