three categories. First, cells may exhibit individual sensing and individual migration (Fig. \[models\]A). Here, each cell can perform gradient sensing and migration individually, although the precision may be low. When many such cells are placed in a group, the group migration can be enhanced and focused by local interactions between the cells. Even if each individual cell has low sensory and migratory precision, the precision of the group as a whole is high due to the interactions. Collisions act to average over the errors in individual cells’ noisy measurements, thereby decoupling group behavior from single-cell properties. This mechanism is often termed “many wrongs,” and it is successful at explaining how group migratory behavior emerges from individual agents that act independently [@simons2004many; @coburn2013tactile]. As discussed later, the failure of a communication-blocking therapy could act as proof that a “many wrongs” method of collective migration is at work in tumor cell invasion.

![image](fig3.png){width=".75\textwidth"}

Second, cells may exhibit individual sensing but collective migration (Fig. \[models\]B). In this mechanism, each individual cell senses its own local environment, and tight mechanical interactions result in the emergent directed motion of the entire group. This mechanism is applicable to the collective migration of connected clusters of cells. 