Social Proof
People look to others' behaviour when deciding, especially under uncertainty.
Definition
One of Robert Cialdini's principles of influence. In ambiguous situations people infer correct behaviour from what others are doing. The effect is strongest when the others are perceived as similar to the observer.
Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.
On this plate
Reach for this when
- Designing product pages, pricing pages and landing pages.
- Building review and rating systems.
- Reducing uncertainty at a decision point.
Common mistakes
- Fabricated or unverifiable proof.
- Proof from a dissimilar audience, which can reduce persuasion.
- Hiding negative reviews.
- Manufacturing activity notifications, which is fabricated evidence and is treated as such by regulators.
Forms that carry weight, strongest first
- Specific reviews from people identifiably similar to the reader, including the negative ones.
- Concrete usage numbers with a real denominator.
- Named customers with a stated use case, rather than a wall of logos.
- Aggregate ratings with the distribution visible, not only the average.
- Expert or editorial endorsement, when the source is credible to that audience.
Negative reviews increase trust
Products with only five-star reviews are read as filtered. Showing the distribution, and letting users read the critical reviews, consistently improves conversion relative to hiding them, because it makes the positive reviews credible.
Forms of proof, and what each is worth
| Form | Weight | Condition |
|---|---|---|
| Review with a visible distribution | High | Negative reviews are shown too, or none of it is believed |
| Named customer with a role and a result | High | Verifiable, and recent |
| Usage count | Moderate | Specific and current. Trusted by 10,000 teams reads as boilerplate |
| Logo wall | Low | Meaningless without saying what those companies actually do with it |
| Real-time activity notices | Low and falling | Widely faked, and readers have learned to discount them |
In practice
- i.
Reviews with visible distribution
EcommerceShowing the full star distribution and allowing users to filter to one-star reviews makes the average believable. Suppressing critical reviews makes the whole set suspect.
- ii.
Named customers over logo walls
B2B marketingOne customer with a stated problem and outcome outperforms twenty logos, because the reader can judge whether that customer resembles them.
- iii.
The perfect rating nobody believed
Why distribution mattersA product showing only five-star reviews converted worse than one showing a four-point-three average with the one-star reviews visible. Uniform praise reads as curation, and curation reads as concealment.
Local chart
PSY·006 · Region I · Grid A2
This entry and the entries it is stated to connect with. Each line is labelled with what the connection means.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
- [1]
Influence: The Psychology of Persuasion
R. B. Cialdini, Harper Business, 1984, revised 2021
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applies when you are designing
Applied through
Where this shows up as a concrete interface decision.
- Ratings and ReviewsPAT·020 · Pattern
Check your work
Review passes that test whether this was done properly.
- Design Ethics ChecklistCHK·010 · Checklist
- Ecommerce ChecklistCHK·006 · Checklist
Related concept
Connected closely enough to change how you apply this.
- Authority BiasBIAS·006 · Cognitive bias
- Framing EffectBIAS·003 · Cognitive bias