Serial Dependent Effects Of Stable And Changeable Facial Attributes

The serial dependent effect is a perceptual aftereffect whereby current visual-perceptual judgments are systematically biased toward the most recent visual experience.For example,an individual will tend to judge the current ambiguous face emotion as happy if they are first presented with a happy emotional face.Many previous studies have found this effect,not only low-level visual features(e.g.,grating orientation judgments)but also high-level visual features(e.g.,facial emotion judgments).The temporal variation features of human faces can be divided into stable ones(e.g.,facial gender and facial identity)and changeable ones(e.g.,facial emotion and eye gaze).A previous study found that there was an attractive serial dependence for stable attributes of faces(e.g.,gender)but a repulsive serial dependence for changeable attributes of faces(e.g.,emotion).However,recent studies have also shown that facial emotions have the same attractive serial dependence.In addition,the repulsive effect of facial emotions in previous studies was based on a small sample size.Thus,whether stable and changeable face attributes have the same encoding strategy and whether the underlying neural mechanisms differ is unclear.In the current study,we used psychophysical experiments and ERP techniques to address these questions.Both variant and invariable face attributes were manipulated,and participants were asked to judge different dimensional features of the same face simultaneously.In Experiment 1,facial stimuli were modulated along gender(male and female)and emotion(happy and angry)dimensions to produce a set of 25 stimuli,according to five levels for each dimension.Each trial started with the presentation of a fixation point lasting for 700-ms at the center of the screen,then test stimulus lasting for 250-ms.Next,a response screen appeared,participants were required to determine as quickly and accurately as possible whether the face was male or female and whether the face was happy or angry;In Experiment 2,using the same experimental paradigm to explore whether this effect persists in other changeable facial attributes.We manipulated the variable attributes of faces(eye gaze)and the invariant attributes of faces(gender)to further investigate.In Experiment 3,the same face stimuli were varied across both gender and emotion dimensions using a single-trial experimental paradigm.Subjects were naive to the experimental task prior to the experiment and only had to make one task judgement at a time to explore the stage of production of serial dependent effects on different face attributes;The Experiment 4 was based on a passive viewing experimental paradigm,recording brain responses of serial dependent effects on different face attributes using ERPs,the aim is to investigate whether behavioural deviations for different face attributes are related to EEG signals in the brain,further revealing the processing stages in which serial dependent effects occur.Results suggest that current perceptions of face gender and face emotion are systematically biased by previously perceived attributes,showing an attractive serial dependent effects(Experiment 1);For the eye gaze direction task,although there was no 1-back serial dependence effect,a positive serial effect was observed for the 2-back,which remained significant until the 5-back(Experiment 2).At the behavioural level,the serial dependence of gender and emotion was independent of decision making and working memory,and was driven by true perception(Experiment 3).At the neural level,previously perceived face information was reactivated at different time points,and neural signals of the attractive serial dependence on gender and emotion were found,suggesting that serial dependence on facial gender and facial emotion occurs at different stages of processing(Experiment 4).Overall,in the four experiments,the dual task judgment response for stable and changeable facial attributes found that there was a attractive serial dependent effects on different face attributes.these results extend previous research,it is demonstrated that stable and changeable facial attributes use integrated visual control mechanisms to maintain the stability of face processing.Furthermore,this serial dependent effect of attraction alters the appearance of facial attributes,acting at an early stage of visual processing.In addition,the results show the existence of partially overlapping neural mechanisms on different face attributes.