The Modify People IDs tool allows you to swap the unique person ID numbers assigned to each person when multiple people are tracked in a trial. Click and drag an ID and drop it onto another ID to swap those two ID numbers. This change to the IDs is immediately visible in the 2D and 3D views. You can also right-click on an ID to display a context menu with options for removing that tracked person or making it person 0. Note: removing a person cannot be undone (except by re-running Track People).