Inversion Effect Of Faces And Chinese Characters In Their Processing Mechanism-Behavioral And ERP Study

For about four decades, behavioral studies have revealed that picture-plane inversion dramatically impairs face recognition, which lead to the discussion of what its essence is. Some people think that the inversion effect is unique to faces, and this finding is regarded as evidence that the visual system uses special perceptual processing for faces different from the processing of other non-face objects. Though the selective face-specific areas in the brain have been found by the electrophysiological and neuroimaging studies, it's still an inconclusive discussion. Other people deem that faces are special, because subjects are required to make visual subordinate-level categorization that concerns expertise in the comparatively homogenous category, and that human beings are expert at discriminating faces at individual levels. Therefore, every category of visual stimuli would show inversion effect, if only people acquire the experise of such visual stimuli. So far, this issue is still the focus of argument.The unique character, Chinese character, has become more and more popular in the visual cognition. Every literate Chinese adult is an expert at discriminating Chinese characters that possess two-dimension features and have advantages over other words as an old type of hieroglyph. It has been found that there is word-specific brain cortex that is named Visual Word Form Area (VWFA) and has effective functions of processing languages. Such findings indicate that there should be anatomic and functional elements of processing Chinese characters. However, more studies focus on the semantic and speech research, the grapheme research is comparatively insufficient, because the effective experimental methods and paradigms are difficult to find, and especially for the research about the early visual processing of Chinese characters themselves.The present research tries to study the behavioral results of inversion effect of faces and Chinese characters so as to compare these two cognitive mechanisms. What's more, the electrophysiological research is also employed to explore the processing stages and features of the faces and Chinese characters further. In addition, such results can be used for reference to make more exploration and trials.The contextual priming paradigm was used in the present study, and the whole research consisted of two main parts: the behavioral study and ERP study. In the former study, four groups of subjects were induced to respond to the same comparison stimuli in two paradigms (faces vs. English letters, Chinese characters vs. English letters), two cognitive conditions (inversion vs. rotation), and two kinds of changes (configural changes vs. featural changes). The latter study, similar to the former, concerned ERP in which subjects were required to judge the orientation of the stimuli. At last, we compared the reaction time, ERP's latencies and amplitudes.Some main conclusions were drawn as follows:We found inversion effect not only in recognition of faces, but also in that of Chinese characters, and the subjects responded to the same stimuli in different ways according to the different contextual priming conditions. The two inversion effects were opposite, which definitely demonstrated that inversion effect of faces was independent of experimental paradigm, however, other stimuli could also show this effect, as long as they acquired the common configuration and were very familiar to the human beings who were able to possess expertise in such stimuli by long-term experience. Therefore, the inversion effect couldn't be regarded as the evidence that there was a unique processing stage for faces. By contrast, our results corroborated thoroughly the explanation of expertise hyhothesis for inversion effect.When we processed the up-side-down faces or Chinese characters, some certain strategies, different from that of processing upright stimuli, were employed, and the shift of the ways of cognitions might happen at an angle of 120 degrees. The regression results showed that there were nonlinear relationships between reaction times and angles. As a rule, the inversion effect only appeared in configural changes and was absent in featural changes, which indicated that inversion mainly impaired the processing of configural information, and such processing made senses in expertise system too.In the model of Bruce-Young, there should be a coarse visual categorization before direct visual processing, configural encoding, and analysis of expression and so on.P1 should be thought to represent an earlier face-specific processing stage as early as 100-120 ms following stimulus onset rather than simply reflect the low-level visual difference. What's more, it might partly concern configural processing. As for the Chinese character, the early perception stage might originate from P1, and have left advantages over right, which might be followed by the bilateral processing.N170 should not be considered as the face-specific component, neither the reflection of low-level visual difference between faces and non-face stimuli. It should be considered as the reflection of expertise.The inversion of the visual stimuli was likely to delay the laencies of faces and Chinese characters; however, the mental rotation might probably influence the amplitudes.To sum up, the cognition of faces and Chinese characters are both crucial social functions in our life, and our research made a meaningful attempt to compare the two important visual stimuli. It's believable that human beings will get more systematic understanding about their neurobiological bases and functions with the development of cognitve neuroscience, brain neuroimaging and electrophysiological technology.