Placebo Validation of Information Treatment Mechanisms
RCTClinical Trial
Field experiments delivering informational disclosures risk confounding pure belief-updating channels with experimenter demand effects, Hawthorne effects, or simple attention shocks.
Picture this
Imagine giving a vitamin supplement to someone who already has perfect vitamin levels; if their health stays completely unchanged while deficient people improve, it proves the supplement works specifically by correcting deficiencies rather than through a placebo effect.
What the evidence says
Disclosing official supervisor salary to workers with accurate baseline beliefs produced no statistically significant change in household visits under either meritocratic (+1.308 visits; p = 0.608) or non-meritocratic (-0.968 visits; p = 0.608) promotion regimes, ruling out attention or demand artifacts.
- Who was studied
- N = 598 Community Health Workers who held accurate baseline beliefs regarding supervisor salary (250,000 SLL) across Peripheral Health Units in Sierra Leone.
- How
- Empirical placebo group comparison within a randomized information experiment, tracking performance changes among workers whose baseline salary beliefs equaled the truth.
What to do
Include pre-surveyed accurate-belief subgroups as empirical placebo controls when designing information intervention trials to rule out attention shocks.
From the source
"As a placebo check, we look at workers who correctly estimated PS pay at baseline and did not update their perception of pay progression in Tpay=1... Revealing the true PS pay has no statistically significant effect on their performance regardless of whether the system is meritocratic..."
Promotions_and_Productivity_The_Role_of_Meritocracy_and_Pay_Progression.pdf