We show a stakeholder some wireframes and talk them through the features. Once they see them they begin to imagine the ways features will look and act based on similar products they have used.
While perfectly natural, this behavior is problematic – what we envision may be nothing like products this stakeholder has previously used. These assumptions your stakeholder makes will lead to you and your stakeholders having different expectations during product development.
You need to make artifacts as real as possible in order to elicit the most unbiased, unimpeachable feedback from users during research. You do not need to build a fully functioning product to validate your idea.You do need to eliminate or reduce the guesswork needed to understand how your product will work.