Cheap Talk: When Words Are Free

How game theory explains when costless statements can still convey useful information, and when they are ignored because incentives differ.

Much of life involves talk: advice, promises, recommendations and warnings. Words cost nothing to say. So when should we believe them? Game theorists call costless, unverifiable messages cheap talk.

The key insight

In 1982, economists Vincent Crawford and Joel Sobel showed that cheap talk can convey information, but how much depends on how well the speaker’s and listener’s interests are aligned:

Fully aligned interests: the listener can trust the message completely. A friend telling you which road has less traffic has no reason to lie.
Partly aligned interests: messages convey some information, but only roughly. Advice may be vague.
Opposed interests: talk is worthless, since the speaker has every reason to mislead.

Examples

A salesperson saying “this is the best phone for you” has incentives to sell more, so buyers discount the claim.
A doctor recommending treatment usually has aligned interests with the patient, but fee structures can create conflicts.
Central banks use forward guidance, which is partly cheap talk, but their reputation for keeping promises makes it credible.
Job references from former employers may be vague when employers want to avoid conflict.

Making talk credible

Reputation: repeated interactions make lying costly in the long run.
Verification: if claims can be checked later, lying becomes risky.
Aligned incentives: fee-only financial advisers, paid by the client rather than commissions, may give more trustworthy advice.
Costly signals: when words are backed by costly actions, like warranties or deposits, they become more believable.

Why it matters

Understanding cheap talk helps you judge advice, marketing and promises by asking: what does the speaker gain if I believe them?

Two advisers

Two people recommend an investment product. One is a friend with no stake in your decision. The other earns a commission if you buy. Their words might be identical, but game theory suggests you should weigh the friend's advice more heavily.

Thinking free statements carry no information

Cheap talk can be informative when interests are aligned, or when reputation and verification make lying costly.

Key takeaways

Cheap talk means costless, unverifiable messages.
Crawford and Sobel showed its value depends on aligned interests.
Reputation, verification and aligned incentives make talk credible.
Always ask what the speaker gains if you believe them.