Wednesday, 3 October 2012

Priming Denialism

The concept of priming in psychology refers to the unconscious effect that a stimulus can have on future behavior. For example, one study looked at the effect that holding a hot or cold beverage before an interview would have on that person's opinion of the interviewer1. The stimulus in this situation is the hot or cold beverage and what they found was that the temperature translated almost directly into our metaphorical way of assessing the behavior of the people we meet; that is, after holding a cold drink people were more likely to interpret their behavior as cold and unwelcoming, whereas holding a hot drink people were more likely to interpret their behavior as warm and welcoming. As the researchers describe it, this is like "holding warm feelings towards someone" and "giving someone the cold shoulder".

Recently, a classic experiment in priming by Bargh, Chen, and Burrows2 was called into question by Doyen, Klein, and Pichon in their paper: "Behavioral Priming: It's All in the Mind, but Whose Mind?"3. The original study looked at the effect that including "old" words in a language task has on the speed at which subjects leave the lab following the experiment, so the expectation was that if a list of words a subject was asked to memorise included words like "old", "grey", or "bingo" (among others) then the participants would walk slower as they leave the room. Doyen, however, suspected that subtle behaviors of the experimenters may have affected the behavior of the subjects and so they attempted to replicate the study with a stricter methodology to rule out a number of possible confounds.

To do this, Doyen gave a set script to all 10 'experimenters' which they were to repeat to the subjects taking part in the study. The interesting twist in this study was that Doyen told half of the 'experimenters' that they should expect their subjects to walk slowly, and the other half that they should expect their subjects to walk more quickly. The 'experimenters' were given stopwatches to time the speed of the participants (as was done in the Bargh experiment), but there were also infra-red sensors that gave a more objective and more accurate measure of the walking speed.

What was found was that the expectation of the experimenter appeared to affect the speed of the subject; that is, in groups where the 'experimenter' expected the subjects to walk more slowly, they recorded the subjects walking slowly, and in groups where the 'experimenter' expected the subjects to walk more quickly, they recorded the subjects walking more quickly. So the behavior of the subjects appears to be a result of the behavior of the experimenters, and not a result of the priming - as the original studies suggested. To explain this, we can look at what is termed the "Clever Hans" effect.

This was originally termed when a horse in 1907 was suggested to have the ability to count - his owner, the audience, and scientists at the time all seemed to accept that when its owner asked him a mathematical question, the horse (Hans) could correctly tap his hoof on the ground a number of times that represents the correct answer (so if the answer is "three", the horse would tap its hoof three times). It wasn't until psychologist Oskar Pfungst tested the horse that it was discovered that, even unbeknownst to the owner, the correct answer was being given by the subtle cues accidentally exhibited by the person asking the question. In simple terms, what was happening was that the owner asked the horse a question, and this was the cue to start tapping its hoof. The owner would then, through excitement or anticipation, behave differently when the horse got closer to the correct answer (for example, leaning forwards, raising eyebrows, clasping fists, and so on), this would be the cue for the horse to stop tapping its hoof.

The debate over whether this study showed a true methodological flaw or whether it was flawed in itself was something that Bargh and Doyen argued over, with valid and invalid points being thrown at one another in the commentary sections of journals. However, the important point that was taken away from the Doyen study, and one that is emphasised in Daniel Kahneman's "Thinking, Fast and Slow"4 where he suggests that there is a "train wreck looming" for priming research, is that there is a fundamental problem with the concept of priming and that the effect itself may not be real.

Ed Yong, a blogger who writes Not Exactly Rocket Science, has written some critical articles on priming and recently emailed psychologist Norbert Schwarz some questions relating to how Kahneman has characterised priming research and possible problems with it, and Schwarz has decided to make his answered public here: Response to Ed Yong’s Questions. On the question of whether the suspicions of priming are warranted, I think Schwarz gives a great response:
There is no empirical evidence that work in this area is more or less replicable than work in other areas. What distinguishes this work from other areas is solely that some of the findings are more surprising to lay people than findings in other domains. Unfortunately, the surprise value of the findings has sometimes been in the foreground of the publications (and has always been in the foreground of popular reports). This gave some particularly surprising individual findings an iconic status that far exceeds their empirical contribution to theory testing. It also focused the popular discussion on individual results and away from the convergence of a large body of evidence, including many findings that are not eye-catching, and the rather straightforward processes that underlie the surprising effects.
This created a context in which the concerns of a few sceptics, focused on one or two iconic findings, received more attention than either the critics’ slim empirical evidence or the relevance of the iconic findings warrants. You can think of this as psychology’s version of the climate change debate: Much as the consensus among the vast majority of climate researchers gets drowned out by a debate created by poorly supported and narrowly focused claims of a few persistent climate sceptics, the consensus of the vast majority of psychologists closely familiar with work in this area gets drowned out by claims of a few persistent “priming” sceptics. Their scepticism is based on isolated nonreplications of individual findings combined with a refusal to acknowledge the results of meta-analyses that count as conclusive evidence in any other area. Their critiques find attention because the findings they doubt are counterintuitive and of interest to a wide audience -- a failure to replicate a ten millisecond difference in a standard attention experiment would never be covered by you, Ed, or your colleagues. Hence, nonreplications in other domains of psychology rarely become the topic of public debate -- that people care in the case of “priming” studies is a tribute to those who put these phenomena on the map in the first place. While much remains to be learned about these phenomena, a response of broad doubt is incompatible with the available body of consistent evidence and its compatibility with related domains of knowledge (as Kahneman’s “Thinking, fast and slow” documents).
Basically, the evidence for priming is, at this point, indisputable. To deny the basic processes of priming requires us to reject a number of core principles of psychology and to overturn such results would mean having to literally rewire the psychology textbooks. As such, I think it makes sense for Schwarz to compare denying priming to climate change denialism. Intuitively, this may seem like a strong claim but it seems to me that this 'resistance' we may initially feel is a result of a resistance of accepting that fields like psychology are comparable to "harder" sciences - so even if a finding is as solid as priming, there is still a belief that the result could be questioned or could be a mistake. 

It's an interesting response from Schwarz though and I look forward to seeing how this debate, and issue in general, pans out in the future.


1. Ijzerman, H., Semin, G. R. (2009). The Thermometer of Social Relations: Mapping Social Proximity on Temperature. Psychological Science, 20 (10): 1214–1220.

2.  Bargh, J. A., Chen, M., & Burrows, L. (1996). Automaticity of social behavior: Direct effects of trait construct and stereotype activation on action. Journal of Personality and Social Psychology, 71(2), 230-244.

3. Doyen, S., Klein, O., Pichon, C., & Cleeremans, A. (2012). Behavioral priming: It's all in the mind, but whose mind? PloS ONE, 7 (1), e29081.

4. Kahneman, D. (2011). Thinking, fast and slow. New York, NY: Farrar, Straus & Giroux.

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