The Integration Of The Two Parts In Two-face During Adaptation

The perception processing of face is one of the most important research fields in Psychology.Although many psychologists do many works in this field,there is no final conclusion in how faces processed.Nowadays,there are two main hypothesis supported by previous research,one suppose that each part of a face is processed independently,no integration occurred.The other says that parts are processed in an interactive manner.More importantly,most researchers only focus on the integration of the top and bottom faces,while ignoring the integration of the left and right faces.Most people’s faces are not symmetrical.Previous studies have found that cognitive systems can extract the average features of face and form a statistical summary representation.Therefore,for the asymmetrical left and right parts,is it independently represented such as "the left eye is large,the right eye is small",or represented as average of the left and right parts is also needed to be explored.In our study,we used the adaptation paradigm.The two-face(one half from one person and the other half from another)was used as an adaptor and the average face was used as tester stimulus to investigate whether the left and right parts of the two-face can be integrated into an average representation.Previous studies have found that adaptation to a face reduces our neural activities on that face.We expect that the N170 amplitude of the average face will decrease significantly after adapting to the two-face.In the first experiment,the individual face,the two-face and the average face were used as the adaptor,and the average face was used as the tester to examine whether the left and right parts of the two-face could integrate during the adaptation.Our experiment includes individual face-average face,average face-average face,two-face-average face three conditions.The average face is formed by averaging all the features of the left and right parts of the two-face.The ERP result shows that the N170 amplitude in the average and two-face condition were significantly larger than N170 amplitude in the individual condition,and the difference between the average and two-face conditions was not significant.That is,the adaptation pattern of these two conditions is consistent,reflecting the integration of the face perception during adaptation.And the two-face was integrated into an average face,because only people’s representation of the two-face and the average face were consistent,then a consistent aftereffect was observed.So it shows that the two-face is integrated during face perception,and the mechanism of the integration is averaging the two parts of the two-face.The result of Experiment 1 may not be due to the integration of the left and right parts,instead,it may because the two-face and the average face contain more same elements than the individual faces.In experiment 2,we use aligned or misaligned two-face as adaptor,and use aligned or misaligned average face as tester,to investigate if only the left and right parts of the aligned two-face can be integrated.The ERP result shows that the difference between the magnitude of the aftereffect of the aligned and misaligned conditions was significant.And the aftereffect in aligned condition was significantly greater than misaligned condition.Since the misaligned and aligned two-face contain the same elements,the effects of the same elements can be excluded.Compared to misaligned condition,the difference between the aligned and misaligned conditions reflects the integration of the aligned two-face.Both experiment 1 and experiment 2 found that the adaptation to the two-face will affect the neural response to the average test face.It shows that during the adaptation to the two-face,the nervous system integrates the asymmetry two-face into symmetry average face,and mechanism of the integration is to form a statistical summary representation during the adaptation.