Brain mechanisms of persuasion: how 'expert power' modulates memory and attitudes

Abstract

Human behaviour is affected by various forms of persuasion. The general persuasive effect of high expertise of the communicator, often referred to as 'expert power', is well documented. We found that a single exposure to a combination of an expert and an object leads to a long-lasting positive effect on memory for and attitude towards the object. Using functional magnetic resonance imaging, we probed the neural processes predicting these behavioural effects. Expert context was associated with distributed left-lateralized brain activity in prefrontal and temporal cortices related to active semantic elaboration. Furthermore, experts enhanced subsequent memory effects in the medial temporal lobe (i.e. in hippocampus and parahippocampal gyrus) involved in memory formation. Experts also affected subsequent attitude effects in the caudate nucleus involved in trustful behaviour, reward processing and learning. These results may suggest that the persuasive effect of experts is mediated by modulation of caudate activity resulting in a re-evaluation of the object in terms of its perceived value. Results extend our view of the functional role of the dorsal striatum in social interaction and enable us to make the first steps toward a neuroscientific model of persuasion.

Figures

Fig. 1

Trial structure. During each trial of the encoding session (day 1), subjects were presented with the photo of a celebrity followed by the photo of an object (product). All stimuli were separated by varying ISI. Subjects were instructed to indicate whether or not they see a link between the celebrity and the object. The gradient bar represents the time when BOLD signal was modelled for each trials. On day 2, recognition memory and attitude towards the object presented in two separate sessions were tested. Finally, familiarity, physical attractiveness and perceived expertise of celebrities were measured (this step is not depicted here). A sketch of a celebrity and not a real photo as used in the study is presented in the figure due to potential copyright restrictions.

Fig. 2

Main effects of attitudes (SAE), memory (SME) and celebrity expertise (A) SAE on neural activation—the contrast of subsequently favoured versus not favoured objects (high vs low estimates of purchase incidence); n = 16. (B) SME on neural activation (parahippocampal/fusiform gyrus)—the contrast between brain activity to later successfully remembered objects (hits) vs forgotten objects (misses); n = 18. (C) Effect of perceived celebrity expertise on neural activation—the contrast of brain activity related to objects that followed experts vs objects that followed non-experts during the period following object encoding. Amg, amygdala; CG, cingular gyrus; DPF, dorsal prefrontal cortex; PHG, parahippocampal/fusiform gyrus region; STG, superior temporal gyrus region; Th, thalamus; R, right hemisphere.

Fig. 3

Persuasive expertise effects on attitudes and memory (A) The interaction of perceived celebrity expertise with SAE. The left panel depicts the interaction in the caudate nucleus. The right panel depicts the averaged fMRI signal for the left caudate nucleus cluster. The averaged fMRI signals for not favoured objects (with low estimates of purchase incidence) that followed non-experts (dark blue), favoured objects (with high estimates of purchase incidence) that followed non-experts (pink), not favoured objects that followed experts (yellow) and favoured objects that followed experts (light blue) are displayed. The averaged fMRI signals were calculated for all significant voxels within the cluster. The error bars depict standard errors of the mean. n = 16. (B) The interaction of perceived celebrity expertise with subsequent recognition memory (SME). The left panel depicts the interaction in the left hippocampus/parahippocampal cortex. The right panel depicts the fMRI signal for the left parahippocampal cluster. The averaged fMRI signals for subsequent misses (objects) that followed non-experts (dark blue), subsequent hits that followed non-experts (pink), subsequent misses that followed experts (yellow) and subsequent hits that followed experts (light blue) are displayed. PHG, parahippocampal cortex. n = 18.