Abstract: Previous studies have found a salient effect of the attentional bias toward neutral infant faces, that was, the attentional bias toward neutral infant faces in adults was the strongest when adults viewed infant faces with different expressions. Meanwhile, this salient effect was affected by the uncertainty in expressions. However, it has not yet carried out an in-depth analysis of the attention processing course of this salient effect and the influencing mechanism of the uncertainty in expressions. Therefore, this project designed two studies with a total of eight experiments to address the above issues. Specifically, based on the different stages and components of attention processing, our team intends to adopt an analysis of the split time courses to first investigate the characteristics of attention processing course in the salient effect of the attentional bias toward neutral infant faces. Then, our team intends to adopt face morphing technique to regulate the degree of uncertainty in expressions, in order to further explore the effect of uncertainty in expressions on the attention processing course in the salient effect of the attentional bias toward neutral infant faces and its neural mechanism. The research in this project will help to reveal how the uncertainty in expressions affects adults’ attention processing course of emotional infant faces and its mechanism, and it is instructive to explore whether the degree of uncertainty in different types of emotional signals affects the attention processing course.