Suggestion Contamination: How Language Shapes Perception

Definition

Suggestion contamination is the phenomenon by which subtle linguistic hints—even individual word choices—influence a person's thinking and memory without their conscious awareness. A coach's tentative suggestion, a paraphrased interpretation, or an embedded assumption in a question can alter how a coachee perceives their situation and remembers events, and these alterations are often permanent.

In the Book

Dunbar draws extensively on Loftus and Palmer's (1974) research on eyewitness testimony to explain how suggestions work in coaching. In their experiments, participants watched a film of a car crash. Different groups were asked slightly different questions: "How fast were the cars traveling when they bumped into each other?" versus "How fast were the cars traveling when they smashed into each other?" The group asked about "smashed" estimated higher speeds—a single word altered perception.

More striking: when asked later "Did you see broken glass?" (which wasn't in the film), participants who had been primed with "smashed" were far more likely to agree they had seen glass. The embedded assumption introduced by the question—that there was broken glass—created a false memory.

Dunbar illustrates this in coaching: when a coach says "What would you like to pay attention to?" the word "pay" metaphorically transforms the question into something the coachee experiences as costly and difficult, potentially evoking memories of school teachers forcing them to pay attention. She emphasizes that once a seed is planted through suggestion, people "cannot take a suggestion back"—even when told the suggestion was designed to influence them, people typically stick to their manipulated belief.

Paraphrasing is another insidious form of contamination. When a coach says "So what you're saying is…" and then uses their own words, they have introduced their interpretation, which subtly shifts the meaning. Rather than "It's too expensive," the coach paraphrases as "You can't yet see how valuable it would be," putting words—and thought patterns—into the coachee's mind.

Why It Matters

This concept explains why even well-intentioned coaches can unintentionally corrupt a coachee's thinking. It reveals that asking questions is not inherently non-directive; biased questions are a powerful form of influence. Clean Language questions are constructed specifically to avoid embedded assumptions and suggestions. Understanding suggestion contamination is why Clean Coaches repeat back the coachee's exact words rather than paraphrasing, and why they carefully craft questions to be free of the questioner's own metaphors and assumptions.