reactance

Telling you not to do it makes it attractive.

A 1977 study by Brehm and Weinraub found that restricting access to a toy increased its desirability to children.

The finding is attributed to the 1977 study 'Physical barriers and psychological reactance: Additional studies', rather than the 1966 book.

Prohibition is often the most effective marketing strategy.

Where this comes from

Study: Jack Brehm, 1966, A Theory of Psychological Reactance
What the check found: The 1966 work is the foundational theory, not the empirical study on toy desirability. That specific experiment was published later.
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.