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The Effect Of One-Sided Arguments On Judgment

In his book, Thinking Fast and Slow, Daniel Kahneman writes about the dangers of only hearing one side of an argument:

The participants were fully aware of the setup, and those who heard only one side could easily have generated the argument for the other side. Nevertheless, the presentation of one-sided evidence had a very pronounced effect on judgments. Furthermore, participants who saw one-sided evidence were more confident of their judgments than those who saw both sides. This is just what you would expect if the confidence that people experience is determined by the coherence of the story they manage to construct from available information. It is the consistency of the information that matters for a good story, not its completeness.

I wonder if the tendency for one-sided arguments dovetails into the planning fallacy and/or illusion of control:

When forecasting the outcomes of risky projects, executives too easily fall victim to the planning fallacy. In its grip, they make decisions based on delusional optimism rather than on a rational weighting of gains, losses, and probabilities. They overestimate benefits and underestimate costs. They spin scenarios of success while overlooking the potential for mistakes and miscalculations. As a result, they pursue initiatives that are unlikely to come in on budget or on time or to deliver the expected returns—or even to be completed.

Still curious? I found this research study on the subject, which says “The results indicate that people do not compensate sufficiently for missing information even when it is painfully obvious that the information available to them is incomplete.”