The Sunk Cost Fallacy

But we already talked about it and we went through all that..."

In my opinion (and based on my experience), the bias created due to a significant and prolonged investment in an idea, concept, or work is the trickiest. It creates a false consensus bias for the entire team as a collective entity. And when I say the entire team, I don't just mean designers. It includes upper management, product managers, and leaders of other teams as well.

I found myself caught in that trap. During those moments, I didn't know how to explain that phenomenon or whether such a concept as a phenomenon even existed. However, I thought that the whole team was under an illusion about a certain thing. It is very easy to slip in that direction.

So, what would be the ways to avoid this?

I assume (the mother of all misleads) that in a perfect scenario, you have another designer (or even a PM) who is familiar with and has essential background knowledge of the problem but has not made that significant investment in that particular case. They can jump in and bring a new, more realistic perspective.

And to what extent does even more frequent testing of the concept itself help? Without, of course, creating additional investment debt.