Both people had to learn to use an interface for scheduling speakers on a calendar GUI. Roughly speaking, in the externalized condition, more problem constraint

Both people had to learn to use an interface for scheduling speakers on a calendar GUI. Roughly speaking, in the externalized condition, more problem constraints were identifiable through visual feedback, while these were absent and had to be inferred in the internalized condition. So, (in this paper), we're talking about planning versus relying on more external visual cues. Your WinZip versus tar example is apt, but it also introduces the issue of GUI versus CLI, which isn't addressed by the paper.