Abstract: Adults’ attentional bias toward infant faces plays a crucial role in forming early parent-child relationships. During interactions between adults and infants, infants express their physiological and psychological states through facial expressions. Adults, in turn, interpret these expressions to understand the infant’s needs. Previous studies have primarily focused on how infants’ positive or negative facial expressions influence adults’ attentional bias toward infant faces. However, the unique impact of neutral infant faces, which often convey ambiguous emotional signals, has been largely overlooked in attention processing studies. In fact, compared to neutral adult faces, neutral infant faces remain highly biologically relevant stimuli. Adults tend to pay close attention to them, demonstrating an attentional bias. This attentional bias, to some extent, helps caregivers avoid missing or misinterpreting crucial signals from infants, ultimately promoting infant survival.===Based on previous research, our studies further found a salient effect of the attentional bias toward neutral infant faces, that is, 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 influenced by the uncertainty in expressions. Although the salient attentional bias toward neutral infant faces has been confirmed, the attention processing course behind this effect and the impact of uncertainty in expressions remain largely unexplored. Therefore, this research primarily aims to outline the attention processing course and its neural mechanisms, which underline the salient effect of attentional bias toward neutral infant faces. Second, it seeks to reveal how the change of uncertainty in expressions influences the attention processing course and its neural mechanisms concerning the salient effect of attentional bias towards neutral infant faces. To achieve these objectives, this research designed two studies with a total of eight experiments.
The first study aims to shift the research focus from the overall attention bias toward infant faces in adults to analyze the different stages and components of the attention processing in the salient effect of the attentional bias toward neutral infant faces. Specifically, this study first investigates the temporal characteristics of different attention processing stages using eye tracking technology (Experiment 1) and its neural mechanisms using functional magnetic resonance imaging (fMRI) technology (Experiment 2). Then, within these attention processing stages, it further explores the unique performance of specific attention processing components using a dot-probe paradigm (Experiment 3) and their electrophysiological mechanisms using event-related potential (ERP) technology (Experiment 4). This study will help reveal the specific processes and mechanisms of dynamic attention processing in response to uncertainty in infant emotional expressions, deepening understanding of the parental brain and advancing the development of social affective neuroscience. Simultaneously, this study holds significant value in guiding the enhancement of the public’s ability to recognize and comprehend infants’ emotions, thereby optimizing parenting behaviors. It also provides a new approach and empirical foundation for designing intervention programs for parents struggling with forming early parent-child relationships, ultimately improving their parenting quality.
The second study aims to regulate the degree of uncertainty in expressions using the face morphing technique to further investigate how the change of uncertainty in expressions influences the attention processing of the salient effect of the attentional bias toward neutral infant faces. Specifically, under the condition where the degree of expression uncertainty is regulated, this study first investigates how the change of uncertainty in expressions influences the temporal characteristics of different attention processing stages using eye tracking technology (Experiment 5) and its neural mechanisms using fMRI technology (Experiment 6). Then, within these specific attention processing stages, it further explores how the change of uncertainty in expressions influences the unique performance of specific attention processing components using a dot-probe paradigm (Experiment 7) and its electrophysiological mechanisms using ERP technology (Experiment 8). This study will shed light on adults’ dynamic attention processing mechanisms in response to varying degrees of uncertainty in infant emotional expressions. This understanding will enrich knowledge of adult responses to infant emotional faces and the social adaptive implications of these responses. Simultaneously, a deeper understanding of how adults process infant emotional faces, especially those with uncertain expressions, can offer valuable insights for scientific parenting advice. This can help the public better comprehend and manage infants’ emotional responses, thereby improving parenting quality and fostering healthy infant development.
In conclusion, this research provides a fresh perspective for exploring how the degree of uncertainty in other types of emotional signals impacts the attention processing of human beings to these emotional signals. This not only expands theoretical understanding of emotional signal processing, but also offers insightful guidance for dealing with emotionally complex social situations such as interpersonal communication and conflict resolution in practice.

Key words: attention, social emotion, infant face, attentional bias, uncertainty in expression