Frontal Alpha Asymmetry

What it is

Frontal alpha asymmetry is taken from electroencephalography. Because alpha power is usually read as an inverse index of cortical activity, relatively less alpha on the left is read as relatively more left frontal activity. The best-known interpretation of that difference is Richard Davidson's approach and withdrawal account, in which relatively greater left frontal activity accompanies approach-related affect and motivation and relatively greater right frontal activity accompanies withdrawal.

The interpretation is one reading of the measure. It is not the agreed reading, and the evidence for it varies with what is being predicted.

It sits close to Reverse Inference, Neuromarketing, The Replication Crisis, Preregistration and EEG Preference Prediction, and is best taken as one idea among several rather than a stand-alone rule.

In effect

In a 2019 meta-analysis, Kuper, Kackenmester and Wacker pooled 79 independent samples and about 5,700 participants to ask whether resting frontal asymmetry works as a marker of personality. It explained less than 0.4 per cent of the variance in extraversion and neuroticism, effects shrank after adjusting for publication bias, and the authors concluded that its validity as a personality marker is not supported.

In a 2019 review, Hakim and Levy listed hemispheric asymmetry among the promising features for predicting preferences from EEG, alongside event-related components, inter-subject correlations and spectral band powers. They advise showing that any neural measure adds predictive value beyond traditional methods.

The Why We Project uses the measure in its article on EEG neuromarketing as a worked case of a signal whose meaning needs to be checked before a feeling is attached to it.

What it does not say

It does not say that a brand can read approval or desire from the two sides of the scalp. The meta-analytic evidence on personality is weak, the link to emotion in advertising is an interpretation, and a pattern in an average of viewers does not describe one viewer. It is one input to a decision, to be weighed with other evidence.

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