The Developmental Trajectory Of Left-side Bias In Faces And Chinese Characters Processing:Evidence From Behavioral And ERP Study

Faces and Chinese characters are common visual stimuli in our daily life,and both are expert stimuli.Previous studies mainly focused on the inversion effect and composite effect.Since the left-side bias effect of faces and Chinese characters was discovered,many foreign researches have discussed the development trajectory of the left-side bias effect of the faces.These researches found that the left-side bias effect of the faces first emerged in 5 years old),and the mature age is different in different tasks,at the latest at the age of 11 to reach adult levels.However,left-side bias effect of Chinese characters is only studied in adults,and the developmental trajectory of the left-side bias effect for Chinese character is unclear.At the same time,there are multi-dimensional similarities between Chinese characters and faces in visual processing.Most importantly,the brain mechanism and development of the left-side bias effect of faces and characters are still unclear.Therefore,this study first adopted a classical simultaneous presentation paradigm to investigate the developmental trajectory of the left-side bias effect of faces and Chinese characters;and then uses EEG technology to further explore the neural mechanisms and development of left-side bias effects of faces and Chinese characters.In this study,there are two experiments to investigate the behavioral and neural mechanisms developmental trajectories of the left-side bias effects of faces and characters.Experiment 1,a classic simultaneous presentation paradigm was used to explore the developmental trajectory of the left-side bias of faces and characters,the participants included Grade 2,Grade 4,Grade 6,and university students.Experiment 2 firstly adopted the sequential matching paradigm to examine the neural mechanism of the left-sided bias effect of faces and Chinese characters for undergraduate,the purpose was to examine the validity of the research paradigm and reveal the relevant EEG components of left-side bias processing;then the Grade 2,Grade 4,Grade 6 children were selected to investigate the developmental trajectories of neural mechanisms of the left-side bias of faces and characters in the sequential matching paradigm.This research found:(1)Experiments 1 and 2 found that there are significant left-side bias effect for faces and Chinese characters in the Grade 2,Grade 4,Grade 6 children and university students.This result showed that the left-side bias effect of both faces and Chinese characters is stable,and the left-side bias effect of Chinese characters emerges from about one year learning experience of Chinese characters.(2)The results of the simultaneous presentation paradigm show that the left-side bias score of Chinese characters is significantly higher than that of faces,and the bias scores on response time of Chinese characters are significantly slower than that of the faces,which indicates there are different processing characteristics for left-side bias effect in Chinese character and face processing.(3)The left-side bias scores showed no significant difference between the participants of Grade 2 and the other participant groups,indicating that the left-side bias of Grade 2 reaches an adult-like level in behavior index in both the simultaneous presentation paradigm and the sequential matching paradigm.(4)The EEG results of the adult participants indicated that the amplitude of N170 and N250 activated by the original faces in the pairing condition of left-side chimeric face with original face were significantly larger than that in the pairing condition of right-side chimeric face and original face,while for Chinese character task,there are significant differences in the amplitude of N170,P200 and N250 component between the two pairing conditions.This shows that the left-side bias effect of Chinese characters and faces are both related to the early cognitive processing process.(5)The EEG results of the children found that,the second grade participants had significant difference in the amplitude of N1 component for two chimeric faces in the face tasks,the fourth grade participants had significant difference in the amplitude of VPP component for two chimeric faces in the face tasks,the sixth grade participants had significant difference in the amplitude of N2 component for two chimeric faces in the face tasks;For the Chinese character tasks,different grades participants showed different activation for the two chimeric Chinese characters on the N170,P200,and N250 components.These results show that there is different developmental trajectory of neural mechanisms in the left-side bias effect of faces and characters.In conclusion,this study found that the left-side bias effect of faces and Chinese characters was reached the adult-like level in Grade 2 by the behavioral experiment,the neural mechanism of the left-side bias processing is mainly related with the early cognitive process stage,and differences in development trajectory of the neural mechanism of left-side bias in faces and Chinese characters processing.