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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