Less explored is the potential the effect could have in other contexts. There are some examples, such as a paper published two years ago by Sophie Parker showing that memory performance was enhanced when participants thought they'd taken a cognition-enhancing drug, even though they hadn't. However, this still has parallels with a medical placebo because of the use of a sham drug.
Now Ulrich Weger and Stephen Loughnan have gone a step further, by showing that a drug-free placebo intervention boosted the general knowledge performance of a group of students. Pub quizzes might never be the same again!
The researchers started by showing 20 participants the answer on-screen to several multiple-choice test items, just prior to the arrival of each of the questions (examples included Pi, and the painter of La Guernica). Next, the researchers gradually reduced the time the answers were presented, until they became completely invisible. This was to demonstrate the principle of subliminal presentation and laid the ground for the experiment proper.
For the real test, involving a new set of 20 questions, Weger and Loughnan told the same participants that for each test item, the correct answer would be presented to them subliminally beforehand, just as in the earlier demonstration. "We further advised them that although they could no longer consciously recognise what was written, their unconscious would still be able to pick up the correct answer," the researchers explained, adding that they told the participants to go with their intuition because "on some level you already know the answer". In reality, however, no answers were presented subliminally, just random letter strings. The researchers call this a "bogus priming method". Participants gave their answers via a paper sheet.
The key finding is that the test performance of the placebo participants significantly outstripped the performance of a control group of twenty students who undertook the test prelims, but were not told the answers would be shown to them subliminally during the test proper (average 9.85 correct out of 20 vs. 8.37 correct; a large effect size of d=0.813). The average age of the 40 participants was 20 years and there were 32 women. The priming placebo effect held when controlling for participant age and gender.
What was going on? The placebo intervention "cannot have expanded the individual's knowledge or storage capacities," the researchers said. "What is more likely to have happened is a weakening of inhibitory mechanisms that normally impair performance on a task - for example, self-incapacitating anxieties that previously taxed cognitive resources." The placebo might also have "primed a success orientation," the researchers said, which may have affected the participants' behaviour accordingly, including increasing their persistence.
Weger and Loughnan are excited about the possibilities their placebo approach might have for testing people's performance in situations where their anxiety might otherwise interfere with achieving their true potential. The real life benefits of this new test-performance placebo will likely depend on the duration of its effect, something the researchers plan to test in future research. Another issue for applying these findings in real life is whether the effect still occurs when people know the trick (at least one previous study has documented a placebo effect that can work without deception). The researchers are optimistic - "we speculate that even the one-off realisation to have skills and resources that the participant was not previously aware of can be a significant insight that may alter the individual's self-perception and self-talk."
Skeptics will no doubt be concerned about the small size of the sample in the current study and the narrow demonstration of the effect. There's clearly a need for replications! As Weber and Loughnan acknowledged, we also need to know more about the mechanisms underlying the improved test performance.
Weger, U., and Loughnan, S. (2013). Mobilizing unused resources: Using the placebo concept to enhance cognitive performance. The Quarterly Journal of Experimental Psychology, 66 (1), 23-28 DOI: 10.1080/17470218.2012.751117
--Further reading--Unleash the crowd within
Resilient, friendly people are more responsive to placebo treatment
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
- Thanks to Marc Brysbaert at Ghent University for the tip-off (he'd love it if you took part in this word association test).
- The journal publishers at Psychology Press are in the process of making this paper open-access.
- Thanks to Jon Sutton for the Mastermind moniker.