Early Neural Markers of Implicit Attitudes: N170 Modulated by Intergroup and Evaluative Contexts in IAT

Abstract

The Implicit Association Test (IAT) is the most popular measure to evaluate implicit attitudes. Nevertheless, its neural correlates are not yet fully understood. We examined event related potentials (ERPs) in response to face- and word processing while indigenous and non-indigenous participants performed an IAT displaying faces (ingroup and outgroup members) and words (positive and negative valence) as targets of category judgments. The N170 component was modulated by valence of words and by ingroup/outgroup face categorization. Contextual effects (face-words implicitly associated in the task) had an influence on the N170 amplitude modulation. On the one hand, in face categorization, right N170 showed differences according to the association between social categories of faces and affective valence of words. On the other, in word categorization, left N170 presented a similar modulation when the task implied a negative-valence associated with ingroup faces. Only indigenous participants showed a significant IAT effect and N170 differences. Our results demonstrate an early ERP blending of stimuli processing with both intergroup and evaluative contexts, suggesting an integration of contextual information related to intergroup attitudes during the early stages of word and face processing. To our knowledge, this is the first report of early ERPs during an ethnicity IAT, opening a new branch of exchange between social neuroscience and social psychology of attitudes.

Keywords: N170; VPP; attitudes; contextual blending; dual valence task; implicit association test; indigenous participants; intergroup context.

Figure 1

N170/VPP and LPP topography and waveforms. (A) Topography maps of VPP component (a central vertex-to-frontal positivity, in red), and N170 component (a left/right temporo-occipital negativity, in blue). Butterfly Montage of average conditions shows both components. (B) Left : N170 (left and right collapsed ROIs) waveforms modulated by structural features of stimuli (faces vs. words); race of the facial stimuli (ingroup vs. outgroup) and word valence (positive vs. negative). Right : Examples of stimuli (ingroup and outgroup relative position faces; positive vs. negative words).

Figure 2

N170 waveform and topography. (A) Indigenous Participants. N170 Modulation based on ingroup-negative association and outgroup-positive association, predominant in the left hemisphere for words, and in the right for faces. Word and Face Topo Maps subtractions (Outgroup-Positive-minus-Ingroup-Negative). (B) The same results are shown for Non-indigenous participants. Notice the same pattern in both groups (except left-restricted lateralization of words in the non-indigenous group), only significant for the Indigenous participants.