4.2. ERPs
Extending reports of Tanaka et al. (2006) and Sommer et al. (2021), the N250 to target faces was larger in the second than in the first part of the experiment. The N250 has been related to facial representations at a certain level of abstraction (Wiese et al., 2021) and the increase across the experiment likely reflects the increasing build-up of these representations. Since our stimulus materials consisted of Asian faces and our participants were Chinese students, the results indicate the culture independence of this increasing face representations.
Interestingly, also the non-target elicited N250 increased from the first to the second half of the experiment. The non-target faces did not have to be explicitly identified at an individual level but only had to be rejected as not being the target face. These results go beyond findings of both the studies of Tanaka et al. (2006) and Sommer et al. (2021), which did not find such effects in the N250 amplitude to non-target faces. We presume that a crucial factor in bringing out the N250 effects to non-targets is the nature of these faces. In contrast to the previous studies, we had controlled the stimulus materials for distinctiveness and can therefore claim that the target face was of low-distinctiveness. Low-distinctive target faces are likely harder to recognize than high-distinctive target faces (e.g., Light et al., 1979). Therefore, it is possible that in order to detect the target face, our participants were forced to scrutinize the non-target faces more than the participants of the previous studies and therefore encoded them incidentally. Attention to a stimulus is a crucial factor in memory encoding.