Mere-Measurement Effect, Defined: When a Question Changes the Answer
The mere-measurement effect is the finding that asking people whether they intend to do something shifts whether they do it. Origin, evidence, and where it fails.
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Ask 40,000 Americans whether they plan to buy a car in the next six months, and more of them buy one than if you had stayed quiet: more than 35 percent more, in the sample later reviews describe. That result, from Vicki Morwitz, Eric Johnson and David Schmittlein (Journal of Consumer Research, 1993), gave the field the mere-measurement effect: asking someone about their intentions or predictions changes the odds that they act, with nothing else done to them. The question is the intervention.
What did the car survey show?
Market researchers had long surveyed people on whether they planned to buy a car or a computer and treated the answers as a forecast. Morwitz and colleagues, in a paper titled “Does Measuring Intent Change Behavior?”, saw that the survey might be moving the numbers it was meant to read. In the sample of more than 40,000 that later reviewers describe, people asked about buying a car bought at a rate more than 35 percent higher than people who were not asked. The result for personal computers was weaker.
Did asking people to predict get them to the polls?
A related result came from Greenwald, Carnot, Beach and Young in 1987 (Journal of Applied Psychology). Students were phoned and asked to predict whether they would register to vote or vote. All who were asked predicted yes, and their records, checked against official voter rolls, showed substantially higher voting than students who had not been called. The authors named that version self-prophecy.
Why would a question work?
The original explanation was that answering makes the attitude behind the intent easier to recall at the moment of choice. Later work added the idea that the thinking needed to answer overlaps with the thinking needed to decide. The effect is stronger when the behavior is easy to imagine and weaker when the question’s persuasive purpose is obvious.
Where does it break?
In 2003 Smith, Gerber and Orlich (Political Psychology) re-ran the voting experiment with 1,160 registered voters in a New England town and found no effect on turnout at low, moderate or high prior turnout. An unpublished 1988 follow-up by Greenwald and colleagues ran two Seattle phone experiments; the first showed no effect, plausibly because turnout was already high, and the second worked among voters with moderate prior turnout.
The effect has not been tested on waking up. The nearest tested analogy is the voting work, and the best reading of it is that asking yourself at night whether you will be out of bed at 6:30 may help a little for easy-to-picture, socially approved actions and is unlikely to rescue someone who has missed the same alarm many times.
A month of self-tracking that leaned on this effect, with a weekly screen-time report as the only audience, is logged in an experiment where Screen Time replaced a friend. To find out whether a nightly yes helps you, write the test down before it starts.
Related questions
Is the mere-measurement effect the same as the Hawthorne effect? No. The Hawthorne effect concerns people changing behavior because they know they are being observed, and its original data have been reanalyzed heavily. The mere-measurement effect needs no observer: a single question about intent, answered once, is enough to shift behavior later, and the proposed explanations are about memory and decision-making, not about being watched.
How big was the effect in the original car-purchase study? Later reviews describe Morwitz, Johnson and Schmittlein (Journal of Consumer Research, 1993) as a sample of more than 40,000 people in which asking about purchase intent raised actual car purchases over the next six months by more than 35 percent (as reported in later reviews).
Does the effect always replicate? No. A 2003 replication of the voter-prediction study by Smith, Gerber and Orlich (Political Psychology), with 1,160 registered voters, found no effect on turnout at low, moderate or high prior turnout. Reviews also report that the effect weakens when the persuasive purpose of the question is obvious and strengthens when the behavior is easy to picture.