Age Differences In Semantic Processing From The Perspective Of Contextual Prediction

Using event-related potentials(ERPs),this study attempts to find brain response differences between young and elderly adults when they engage in semantic processing in the presence of contextual information.According to the semantic processing theory,language users process messages either in an integrative manner or in a predictive manner.Integrative processing or bottom-up processing refers to processing in the course of stimuli presentation,while predictive processing or top-down processing refers to processing before information presentation.A number of previous studies suggest young adults prefer to adopt predictive processing in naturalistic reading settings,while their counterparts tend to use the opposite.However,consensus on this conclusion is yet to be reached.Based on the current research gap,three research questions are of interest here:(1)Are elderly adults equally competent in using the predictive processing mechanism?(2)Are elderly adults capable of inhibiting semantic irrelevant information though they suffer from cognitive degradations?(3)Will elderly adults display individual variability under the same experimental condition? This experiment features 1 × 3 design,that is,three different semantic fillings preceded by the same contextual information——semantically congruent,unrelated and incongruent fillings.(e.g.He spends all day long in the library,because he is a very hard-working/lively/lazy student.)First of all,as the research results turned out,elderly adults elicited the largest N400 effect and even prolonged the effect to 600 ms under the semantically incongruent condition,which was thought to echo the top-down processing mechanism.Before the presentation of visual stimuli,they had already anticipated what was going to appear.Therefore,when the presented word was beyond their expectation,they would have difficulty with integration.In contrast,young adults invoked P600 effect,a component considered to be associated with semantic monitoring and reprocessing in this context.Secondly,when elderly participants were processing semantically irrelevant information,they failed to distinguish it from the semantic congruent condition.That is why they didn't elicit any brain component,which might have something to do with the distribution of their cognitive resources.Expectedly,young adults had a moderate N400 effect,indicating their sensitivity to semantic irrelevance.Finally,after individual variation analyses,both age groups were found to have displayed two different brain response dominance,N400 response dominance and P600 response dominance.This result reflects the shortcomings that are inherent in grand average analyses,but it also entails further confirmation.These results demonstrate that elderly adults have preserved their abilities to process information predictively with the help of linguistic context,but it also depends on specific experimental tasks.When experimental tasks expect too much of them in terms of the distribution of cognitive resources,such as working memory,semantic integration and attention,they will fail to use the context efficiently.These study results will offer a general picture of elderly adults' predictive language processing ability to the whole society and also lay a solid foundation for conducting relevant aging research.As a new research method,individual variation analysis also hopes to provide a new perspective for future electrophysiological studies.