Abstract: For the explanation of the mental processing of aesthetic experience and judgment, one mainstream view was called the fluency theory of aesthetic pleasure, which held that the ease with which stimuli were processed could induce positive emotions, and thus promoting positive evaluation. However, the conceptual development and empirical research in the past 20 years have shown that it cannot explain all aesthetic judgments, especially those complex phenomena related to aesthetic experience. The reason lies in two main aspects. On the one hand, empirical aesthetic evidence from outside the field of visual arts was rather scarce. On the other hand, it is doubtful whether the experiment results based on simple stimuli could be applied to communicative interactions with complex artworks. Furthermore, the idea that processing fluency directly influences aesthetic judgment is also questioned. In addition to aesthetic pleasure, the outcomes of aesthetic judgment also involve stronger positive reactions such as being moved, fascination, as well as more complex aesthetic emotions such as indifference, while little evidence showed that processing fluency led to intense positive reactions.
In recent years, researchers have emphasized the influence of expectation and epistemic motivation on the processing fluency of aesthetic judgment. On the one hand, aesthetic judgments depend not only on processing fluency itself, but also on individuals' expectations of fluency. Compared with other models related to expectation, the predictive processing frameworks (PPF) has a more general and detailed elaboration of lower-level perceptual activities, which allows for a better explanation of the psychological mechanisms of processing fluency. The contribution of PPF to the fluency theory of aesthetic judgment can be mainly reflected in two aspects: one is to help explain the psychological mechanism of processing fluency, the other is to provide a generalized view of fluency and its emotional function. In contrast to earlier theories of fluency, PPF offers a new explanation of the source and psychological mechanism of fluency, that the dynamics of stimuli fluency change as a function of the predictive model of the brain's current activation. In other words, the fluency of stimuli is not stable, but rather dynamically changes as a function of the perceiver's current expectations.
On the other hand, the challenge faced by early fluency theories in the field of aesthetics was that people sometimes appreciate unexpected, novel, and complex artworks. The fluency theory of aesthetic pleasure and PPF alone cannot explain this phenomenon because it is the same challenge that both face in the field of aesthetics. Therefore, for artworks with obvious disfluencies, the outcome of aesthetic judgment also depends on whether the perceiver is motivated to evaluate or reduce the disfluencies by further processing aesthetic stimuli, which inspires us to explain individuals' preferences for the fluency of stimuli from the perspective of epistemic goals by integrating the epistemic motivation model (EMM) in the field of cognitive motivation.
On the basis of incorporating insights from PPF and EMM, it is expected to revise and update the original hedonic fluency theory into a multi-model integrated fluency interpretation framework for aesthetic judgment. In general, the processing of aesthetic judgment involves two consecutive phases: an initial automatic phase and a subsequent control phase. The former of which is manifested in the influence of expectations on the experience of fluency and the perception of stimuli, and the latter of which is manifested in the shaping of epistemic goals on the perception of fluency and aesthetic response. Specifically, the expectations include not only expectation of aesthetic object itself, but also expectation of processing fluency. The epistemic goals include both directional goals and non-directional goals, all of which have the potential to influence how fluency is involved in aesthetic judgement and what specific effect it will have.
By integrating perspectives from PPF and EMM, the framework can better explain the contradictory and complex fluency effects in the process of aesthetic judgment. Importantly, the perspective of multi-model integration not only provides theoretical support to better explain the paradoxical and complex fluency effects in the process of aesthetic judgment, but also points out the direction for future empirical research in this field.

Key words: aesthetic judgement, processing fluency, expectation, predictive processing, epistemic goals