Saturday, August 10, 2013

Save Us From Misleading Press Releases

Exposure to subliminal cues can help us choose the apple instead of the cake. Or can it...  Let's take a look.

Our Brains Can (Unconsciously) Save Us from Temptation

Aug. 8, 2013 — Inhibitory self control -- not picking up a cigarette, not having a second drink, not spending when we should be saving -- can operate without our awareness or intention.

That was the finding by scientists at the University of Pennsylvania's Annenberg School for Communication and the University of Illinois at Urbana-Champaign. They demonstrated through neuroscience research that inaction-related words in our environment can unconsciously influence our self-control. Although we may mindlessly eat cookies at a party, stopping ourselves from over-indulging may seem impossible without a deliberate, conscious effort. However, it turns out that overhearing someone -- even in a completely unrelated conversation -- say something as simple as "calm down" might trigger us to stop our cookie eating frenzy without realizing it.

The press release states that overhearing a message of restraint in a background conversation might prevent us from reaching for a second piece of cake at the holiday party. What's the evidence for this?

A study by Hepler and Albarracin (2013) recorded EEG activity (brain waves) while 20 participants performed a "go/no-go" task that tests their inhibitory control abilities. The subjects responded every time they saw an "X" on the screen but refrained from responding when they saw a "Y". These target letters were preceded by a visual masking stimulus (&&&&&&) for 16.7 msec, a subliminal prime word for 33.4 msec, and then another masking stimulus (&&&&&&) for 50.1 msec. The idea here is to show the prime word very briefly and to "mask" conscious perception of the word.

The prime words were general action words (go, run, move, hit, start), general inaction words (still, sit, rest, calm, stop), and control stimuli (scrambled action and inaction prime words – e.g., rnu). One obvious hypothesis would be that exposure to the masked inaction words would make you better at inhibiting a response to "Y". The authors didn't exactly say that, instead predicting that the amplitude of the P3 component extracted from averaged EEG on no-go trials would reflect the engagement of unconscious inhibitory processes.

However, if behavior is unaffected by the masked inaction words, it ultimately doesn't matter what happens to the P3 component. There is nothing you can say about "resisting temptation" -- behavioral change is not the same thing as a change in the size of the P3 component. The latter may indicate that a subject's brain registered sit, rest, calm, or stop implicitly, but this neural activity wasn't enough to improve stopping ability.

And in fact, this is exactly what the study demonstrated. The masked primes had a modest effect on the size of the P3 wave to the subsequent no-go stimulus, which reached its peak at around 400 msec post-stimulus (i.e., less than half a second after the "Y"). The inaction primes were significantly different from the action primes, but neither one differed from the neutral condition.1

Fig. 1. (Hepler & Albarracin, 2013). Grand average waveforms at electrode Cz to correct no-go trials in Experiment 1. 

The authors interpreted this effect to indicate that inhibition processes were "engaged" by the subliminal primes.

However, the primes had absolutely no impact on how well participants could resist responding to the no-go stimuli [F(2, 38) = .00, p = .99]. Accuracy in the inaction prime condition was exactly the same as in the action prime condition. In other words, the study showed that Our Brains Cannot (Unconsciously) Save Us from Temptation.

Or as succinctly stated by Justin Kiggins on Twitter:

I did not intend to nitpick about the details of this particular study or to single out the authors. But the press release provided by the University of Pennsylvania Annenberg School for Communication is completely misleading (and poorly communicated).


1 This is somewhat problematic, because you'd rather see each of the experimental conditions differ from the control condition.


Hepler J, & Albarracin D (2013). Complete unconscious control: Using (in)action primes to demonstrate completely unconscious activation of inhibitory control mechanisms. Cognition, 128 (3), 271-9 PMID: 23747649

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At August 10, 2013 9:47 PM, Anonymous Anonymous said...

And even then, IF a inhibitory part of the brain were to be activated there is absolutely no guarantee it'd make it through to the decision cue being overridden by 'aw what the heck' signal.

At August 11, 2013 1:42 AM, Blogger Neuroskeptic said...

The Last Temptation of Cz

At August 11, 2013 4:11 AM, Blogger Unknown said...

I do intend to nitpick the study itself: a better interpretation of the data pattern than what the authors proposed might have been "hardly any differences in brain responses and behavior following unconscious priming using (in)action primes".
Doesn't Cognition have a policy of demanding effect sizes, by the way? All I see here is p values and non-significant r's.

Furthermore, labelling the P3 as "inhibitory" is a bit head-over-heels (Nieuwenhuis et al., 2005).

At August 11, 2013 7:19 AM, Anonymous Anonymous said...

I have never read a press release from an institution that wasn't misleading.

At August 11, 2013 7:51 AM, Anonymous Anonymous said...

I have not read the paper, but the word in the different conditions are not counterbalanced by design. Psycholinguists know well how tough it is to match two sets of words for lexical variables. It could just be a simple lexical effect on an overlapping N400, due to word sets that are mismatched along some variable that affects N400 amplitude. Even if it wasn't, the interpretation in the press release is totally bogus.
Good job Cognition, give ERP papers to reviewers who know nothing about ERPs and that's what you get. Nowadays, every idiot thinks they are experts with some technique just because they attended a 2-day bootcamp, if even.

At August 11, 2013 10:59 AM, Blogger The Neurocritic said...

Thanks for your comments. I was more concerned with the complete inaccuracy of the press release in this post than the details of the study, but here are a few specific thoughts...

Jona - I agree, it would have been nice if effect sizes were given (and actual values were reported for no-go accuracy). On the inhibitory front, there is some evidence that the no-go P3 is related to inhibitory processes, although this is disputed (as you noted).

Anonymous of August 11, 2013 7:51 AM - The action and inaction primes were matched for frequency, according to the authors. The participants saw each word about 50 times. There might be a difference in the negative wave occurring about 200 msec post-target onset (that would be about 283 msec post-prime onset), although I'm not so sure this is N400. The meaning of the action words does conflict with the goal of not responding on no-go trials (some more directly than others). That negative blip is slightly larger for action vs. inaction, but I'd expect action to differ from control (which appear to be non-pronounceable nonwords).

At August 12, 2013 2:15 AM, Blogger Unknown said...

Anonymous, the ERP methodology isn't badly done here, it's standard pre-processing in a fairly standard paradigm. (Of course, normal science isn't necessarily good science.)

Neurocritic: almost everything following a no-go stimulus is somehow "related to inhibitory processes" I would argue. Doesn't mean *the* P3 is inhibitory (it isn't).
Also, I think Anonymous meant to imply that the supposed P3 peak effect comes from a superimposed N400 (resulting in a reduced positivity) to the primes. (I don't think so.)

At August 12, 2013 10:56 AM, Blogger The Neurocritic said...

Jona - I just meant to say that the authors weren't completely off on asserting a relationship to "inhibitory control processes" based on the existing literature (although their formulation is rather vague). For instance, "the Nogo-P3 appears to be linked to inhibition of motor response" (Gajewski & Falkenstein 2013). Other researchers may disagree.

I wasn't sure what the overlapping N400 comment meant, given that there is no trace of a negative deflection overlapping with P3. And the other negative blip is rather early (and doesn't exactly behave like a no-go N2, either).


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