"Primed by expectations – why a classic psychology experiment isn’t what it seemed"

Primed by expectations – why a classic psychology experiment isn’t what it seemed
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To test that idea, Doyen repeated his experiment with 50 fresh volunteers and 10 fresh experimenters. The experimenters always stuck to the same script, but they knew whether each volunteer had been primed or not. Doyen told half of them that people would walk more slowly thanks to the power of priming, but he told the other half to expect faster walks. Again, he measured the volunteers’ speed with infrared sensors, but he also gave the experiments a stopwatch to take some back-up readings.

When Doyen looked at the data from the infrared sensors, he found that the volunteers moved more slowly only when they were tested by experimenters who expected them to move slowly. If Doyen relied on the experimenters’ own stopwatch-based measurements, things were even worse. The ones who anticipated faster walks measured faster walks. The ones that presumed slower walks found those too. Let that sink in: the only way Doyen could repeat Bargh’s results was to deliberately tell the experimenters to expect those results.
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Doyen’s study doesn’t show a radically new flaw, or one that’s unique to this branch of social psychology. We’ve known for over a century that scientists can very easily bias their own experiments, even in the most carefully controlled cases. “It’s a neat paper that re-emphasises some highly important and widely relevant warnings for everyone who might want to conduct experiments with people,” says Stafford. “Expectations – participants’ and experimenters’ – and inaccurate measurement can combine to give you biased results.” Ackerman adds, “It’s a lesson that behavioural researchers are all trained in, but one that bears repeating from time to time.”