Considerations for using ERP methods
Mounting evidence shows that ERPs are valuable measurement method across different cognitive disciplines including social psychology (Luke, 2005). Our study review also shows that ERP studies provided additional information on semantic violations and schema violation. The ERP temporal resolution and direct manner puts it at an advantage over other neuroimaging tools such as fMRI , PET and traditional measurement methods such as behavioral and explicit measures, in that it provides online or real time changes in neural activity (Gratton, & Fabiani, 2001). Therefore it has become the most widely used tool to be paired with behavioral measures (Luck, 2005). Other additional factors that make ERPs a better a convenient method to use in general is that they are cheap, are not high maintenance, data is collected in an ecological position and it can be adapted to fit different experiment paradigms (Luck, 2005; Peterson, & Harmon-Jones, 2009; Luck, & Kappenman, 2011). This makes the ERP a convenient tool to use in social cognition. However, the ERP technique has a couple of disadvantages. The main disadvantage of ERPs is the low spatial resolution. Another major concern with using ERPs is the limited interpretation that the results can provide about psychological events involved because the relationship between ERP psychological activity and recorded potentials is not direct (Amodio et al., 2004; Dickter and Bartholow, 2010). Therefore the relationship may be more complex. Several researchers have also expressed concern over the different preprocessing steps used for ERP data as being the main contributor to the inconsistencies found in ERP results (Duncan et al., 2009; Rousselet & Pernet, 2011).
This review set out to discuss the role of N400 on incongruity especially in stereotypes violation. The results show consistency across a large body of literature. The N400 amplitude is larger for incongruent compared to congruent trials. One possible explanation for the N400 effect may be the difference in accessibility to associative memory by the congruent and incongruent condition (White, et al., 2009). The general interpretation of all these results is that we hold association between traits, ideas, beliefs and objects, people or groups. These associations are in our schema and therefore represent the stereotypes that we hold. Based on this, stereotypes can be defined as “specific class of semantic association sorted by memory” (Amodio, 2008; White et al., 2009; Wang, et al., 2010). Other researchers equate stereotypes to accumulated experiences or knowledge about the world (Contreras, Banaji, Mitchell, 2011). It follows that when we are presented with information that is inconsistent with the current association held in our mental frame, we find it difficult to make the new association (incongruent condition). This difficulty is caused by the fact that the new association is hard to retrieve from semantic memory. Using behavioral studies we can differentiate between the consistent and inconsistent association by looking at the time it takes to make the association in implicit tasks. However, sometimes the RT difference in the reaction between the congruent and incongruent condition is not significant or asymmetric across groups. The ERP technique is provides a more robust way to follow the time course for the processing steps needed to produce the difference in reaction times. Thus stereotype studies employ ERPs to get more insight about the mechanism underlying the accessibility of stereotypes, especially in N400 component which is also involved in integration of sematic stimuli and ease of retrieval of information from semantic memory (Kutas and Hillyard, 1984; Kutas, & Federmeier, 2000; Amodio, 2008; White et al., 2009; Wang, et al., 2010; Kutas,& Federmeier, 2011). Since N400 has been reported to be modulated by semantic information violation, difficulty of accessing information from semantic memory, then it should be modulated by the introduction of stereotypically inconsistent information or stereotype violation (Bartholow, et al., 2001). This means that N400 effect may reflect access to associative memory and also integration of information. Hence the N400 can be used as an index of stereotype incongruities.
The review showed that EEG is a potential tool in the research of stereotypes and that N400 could be used as a way to further examine the neural activities involved when processing stereotypes, Even though ERP is a valuable tool in social cognition, we suggest that multilevel approach would provide more valuable insight and control for shortcomings of each tool. Future studies should employ a multilevel approach to explore how stereotypes form, change, and influence behavior.