In the beginning of a project, the plan is laid out by someone. Often times, a product manager or an executive make the plan and communicate in a way that leaves some key assumptions unstated. Without explicit statement, people naturally close the gaps and make their own assumptions. It’s call closure and everyone in the world does it.
You might say that people are supposed to ask questions and make sure they have a consistent set of assumptions. Unfortunately, this rarely happens for multiple reasons. First, people don’t want to appear stupid and planning sessions often encourage people to sit and listen rather than really dig into the details. Not many people have the guts of Tom Hanks in “Big” when he said, “I don’t get it!” Second, people don’t even realize they are filling in the gaps invisibly in their head.
See illustration below:
At first, you don’t notice the divergence in assumptions. After time the chasm widens. The gap grows quickly until you start arguing about some detailed decision. Arguments start sprouting up all over when the realization comes that core assumptions have been different all along.
Clearly this is a bad outcome. But what can you do? It’s way too late to go back to square one. For me, the only time to solve this is at the early stage. Designers should make early storyboards that go into detail about the whole product. They don’t need to be 100% right, but they need to lay down the gist of the story. You can’t just show part of the solution. You need to detail the whole thing, so assumptions are more clearly surfaced.
Lastly, when you realize their is a gap, try and have the conversation be about core assumptions and not about some feature. Figure out where the assumptions are different and you will be able to decide and move on.