Facial expressions are common social information in daily life. There are six fundamental expressions, among which the surprised expression is rather special, which can represent both sudden threat (e.g., car accident) and unexpected surprise (e.g., birthday party) events in our life. Accordingly, the valence of surprised faces is ambiguous, and the recognition to the valence of surprised faces can reveal the pattern and differences of individuals when they process the emotional information with ambiguous valence in their social life.

At present, most of the research materials about valence recognition of surprised expressions are derived from multiple standardized sets, and face materials are usually presented statically. In addition, experimental paradigms adopted by the related researches are very simple, that is, to present a face and ask the participants to select or rate its valence. Although the surprised face has no clear valence information, however, when it is presented without context, the individual will hold negative default interpretations, and positive interpretations may then require an additional regulatory process. If the surprised face is placed in the contextual information, the emotional context (e.g. statement, color and face) could induce the recognition of its valence, that is, surprised faces are identified as positive in positive context and as negative in negative context, and the induction is unconscious and automatic. In the non-emotional context, the increase of the cognitive load selectively alters the hand movement trajectory in indicating affective interpretations, whereas the subjective interpretations remain consistent across variable cognitive loads. And with the rise in stress reactivity, the subjects will hold a stronger negativity bias of surprised faces. In the meantime, some unpredictable non-emotional backgrounds exist in real life, which will cause individuals to hold negative interpretation when recognizing the valence of surprised faces. Besides, the interpretation of a particular facial expression is affected by individual differences. First, the age exhibits a positive trend when individuals recognize the valence of surprised faces. The older the age, the greater the percentage of the individual identifying it positive will be. Second, the processing methods have an effect on the valence recognition of surprised faces, individuals who fixated the mouth earlier exhibiting increased positive ratings. Lastly, personality traits also affect valence recognition of surprised facial expressions. Individuals with trait anxiety tend to have negative interpretation bias of surprised faces, while schizophrenics are not significantly different from the normal people in processing surprised faces and its context.

The valence recognition of surprised expressions has achieved considerable research results, whereas some defects remain. The following aspects can be considered to conduct the subsequent study. First, we should improve the validity of face materials. The ambiguity level of surprised face materials requires further evaluation and exploit more dynamic face materials to improve the ecological validity of experiments. Second, subjects with negativity bias can develop positivity bias by spending more time in the reappraisal of surprised faces. Future research should employ this method to provide new research perspectives for patients with negativity bias in psychiatry.