AcademicJournal of Consumer Research, 2024

"Probably" and "I believe" persuaded more than "possibly" and "I guess"

Positioning & messaging

Reader Note:: This is the paper's cross-study conclusion rather than a single experiment's result. The wording it calls higher-likelihood suggests stronger odds — its examples include "probably," "I believe," "arguably" and "almost certainly" — against lower-likelihood wording such as "possibly," "I guess" or "it feels like." Outcomes varied by study and included product ratings, willingness to buy, article choice and seven-point persuasion scales. The paper's own explanation is perceived confidence: stronger wording made the speaker seem more certain, and mediation analyses in Studies 1, 3, 4A and 4B report that this perception fully accounts for the difference in persuasion. The paper gives no single pooled effect size across all studies, and does not say when the studies ran.
Evidence:: Experimental
Vendor interest:: None
Sample:: Six online experiments, mostly with Prolific participants; disclosed samples include N=15, 21, 111, 111, 400, 527, and 456, plus 3 independent coders in Study 1.

Good for

Backing budget and pricing decisions in similar situations.

Not for

Situations far from the one tested, without checking again.
This was measured in one market. It may not hold where you are.
The source never says when this data was collected. It could be considerably older than the publication date suggests.
This is an aggregated or average number that covers very different cases. Real results in a particular segment may differ.

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20%

chose the recommended article when the comment said “I guess this will be a great article” — against 63% for “I believe” and 63% for no qualifier at all