In late summer I had the pleasure to talk to Antonia Hamilton. She is Professor of Social Neuroscience and heads a research group at UCL’s Institute of Cognitive Neuroscience. Our conversation was clouded by my dismay at having just come across the assertion that social priming doesn’t exist, when I had cited such effects on numerous occasions in the past. Apparently there had been a string of replication failures. But what Antonia said made me sit up with renewed interest.
AH: Social priming certainly can exist! But if you replicate a study and you don’t replicate the results, the important thing is to find out why. Just saying “We failed to replicate study X” is not good enough. It should be the beginning of an investigation. Yin Wang and I did this by looking at the effects of social priming on mimicry.
UF: As far as I remember, the idea originally was that we mimic more when we are primed to feel prosocial. Presumably this is because we are trying to show we are nice people by affiliating with other nice people and do the same as they do. The opposite should be the case with anti-social primes.
AH: But two studies done at the same time in different labs, one of them our own, got completely different results when testing this hypothesis. Continue reading Social priming – does it even exist?
UF: So rather than crying non-replication, you did something extraordinarily constructive.
AH: We looked at the literature on social priming and saw that there is a hidden factor. The prime, whether nice or nasty, had to be relevant to the Self. If it was just nice or nasty, this by itself did not lead to the effects originally reported.
UF: I see – mimicry is not born from our desire for affiliation, but from our desire to have a good reputation. But how do you make the prime relevant to the Self? Given that priming is supposed to happen at an unconscious level, you can’t just say “pay attention, this is all about you”, can you?
AH: Nothing like that! We stuck with a standard task, scrambled sentences, with either pro-social or anti-social content, which you had to complete. In one case the sentence was about other people (3rd person), for instance: “John gives Laura a warm and affectionate hug”, and in the other case it was about you (1st person); “You give Laura a warm and affectionate hug.” For a baseline there was also a neutral non-social version e.g. “A rainbow is made of 7 different colours”. Have a look at the left side of the Figure.
Now look at the right side of the Figure. After the slightly effortful task of unscrambling a batch of sentences, there is another task. You have to press a button with either your index or middle finger. If the number 1 appears, you lift your index finger, and if 2 appears you lift your middle finger. At the same time, you observe in the background a video of another person pressing a button. This could either be using the same finger, or a different finger from what you are asked to do. From previous work we know that people are faster when the other person is doing the same movement and slower if it is the opposite. This is a reliable difference in speed and is known as congruency effect. It tells us about the strength of the tendency to mimic another person’s actions.
UF: Fiendishly clever! You are using a trusted task, by which you can tell how strongly a person is induced to mimic. The question is, does this depend on the type of social prompt that the person received just before pressing the button? Let’s see the results.AH: As you can see in the figure, it does depend! There is a mild congruency effect after the participants have unscrambled and completed non-social sentences (the white bar). The effect is much stronger after being prompted by antisocial sentences in the 3rd person (the black bar on the left), and after being prompted by prosocial sentences in the 1st person (the grey bar on the right).
UF: Amazing that a subtle thing makes such a difference, reversing the congruency effect.
AH: We did another experiment where priming was done via cartoons and this had exactly the same effect. You were told that, after you had seen one cartoon, that you had to write down what happened from the point of view of the protagonist (1st person: ‘I am helping …`) or from the point of view of an observer (3rd person: ‘the white sphere is helping …’). The protagonists either helped (prosocial) or hindered someone (antisocial).
UF: Let me see if I get this right: social priming is about priming the Self for subsequent action? It is not about affiliation! That hypothesis would have predicted that mimicry is always stronger after prosocial content.
AH: The Self priming idea neatly explains a typical failure to replicate. This theory wins over the theory of Goal priming, e.g. affiliation. We mimic when we want to show that we are a nice, trustworthy person, and not like that nasty, anti-social other person.
UF: You also put people in the scanner while they did this experiment. What did you find?
AH: First, we replicated our behavioural results, which is an important indicator that they are robust. And the brain activity we see is entirely in line with the Self priming theory: we see activity in the medial prefrontal cortex (mPFC) that is known to be concerned with processing Self-relevant information. This is during the finger tapping phase when people are controlling the tendency to mimic. More importantly, we found that activity of this same region in the priming phase of the task, was related to the size of the behavioural priming effect. This was true in each participant, and so we can directly link mPFC to the behavioural priming.
UF: I can breathe a sigh of relief. Social priming does exist, and we can point to its specific neural basis. A pity that I so quickly became skeptical after reading about non-replications, but maybe this is itself an effect of social priming. What I’m speculating here is this: We have by now heard too often that our favourite effects can’t be replicated. This has put a dent into beliefs that we have held dear, clearly a Self-relevant sentiment. Just thinking of the concept of social priming made me feel dismayed!
AH: Maybe… In any case, it is time to get over simpleminded denigrations of social priming. It is far more satisfying to know why a replication has failed and which theory best explains diverging results.