Research On Cognitive And Neural Mechanisms Of Hierarchical Relationship Of Class Concept

Class concept is the cornerstone of people's everyday thinking activities, and hierarchical network structure formed by different levels of class concept is the internal psychological structure of people's basic knowledge of the world. People enrich their understanding of the world through learning continuously class concept and eventually improve their own knowledge system. Based on the hierarchical network structure formed by this class concept, people are constantly engaged in everyday classification, reasoning, problem solving, decision-making and other higher cognitive activities. Therefore, it is very important to explore how individuals process hierarchical relationship of class concept in order to further understand the processing mechanisms of a variety of higher cognitive activitiesSince Rosch et al (1976) proposed the processing advantages of the basic level class concept, researchers launched a series of studies and obtained a lot of research findings for the preference processing issue among class concept levels. But on the whole, there is big controversy among its results. Firstly, influenced by typical degree of experience and materials, the subordinate level of class concept also shows some processing advantages. Secondly, for typical materials and processing of different class concept hierarchy, there are two different processing preference orders:one is the processing order of "Basic-superordinate-subordinate" in which the basic level of class concept is in preference position; the other is the processing order of "superordinate-basic-subordinate" in which the superordinate level of class concept is in preference position. So far, there is little research on the second processing order with a single research paradigm. In addition, there are a handful of researches on the neural mechanisms of class concept hierarchical processing with the research paradigms beinglimited to "familiarity/novelty preference paradigm" and "rapid visual search task", and most of them concentrated in a separate discussion of some hierarchical class concept processing. Also, there is a lack of studies investigating the three kinds of class concept hierarchies of subordinate level, basic level and superordinate level in one experiment.This study attempts to discuss the impact of the three different levels of class concept on the tested class concept hierarchy processing preference with identical experimental materials, and to provide richer and more direct experimental evidence for class concept hierarchy preference processing effect. Therefore, this study explored cognitive and neural mechanisms of different hierarchical relationships of class concept in three different task paradigms (semantic masking task, semantic priming task and category-based reasoning task), by using the traditional behavior method and event-related potential (ERP) techniques with high time resolution.The whole studies are divided into three parts in details. The first part consists of Experiment 1 and 2 using behavioral method and ERP technique respectively, aiming to examine the recognition and neural mechanisms of hierarchical relationship among class concept in a "semantic masking task". In this task, different levels of class concept were used as priming words, masking words and target words. After presenting a priming word with a very short time (60ms), a masking word followed for 80ms, and finally the target word was presented. Subjects were asked to determine whether the target word was the same as the priming word. When judging the target word, subjects needed to take the priming word-related information, we speculate that different levels of masking words would affect the extracting of the priming word information. This study aimed to examine different class concept hierarchical relationship for subjects' behavioral responses and EEG responses in the semantic masking task, by changing class concept hierarchical relationship between priming words and masking words. The results of Experiment 1 are as follows:(1) The class concept hierarchical distance between priming words and masking words had different impacts on the semantic masking effect, that is, the closer the class concept hierarchy was, the better the masking effec wast, perhaps due to the higher "mental representation coincidence degree"; the more difficult to recognize the target words, the longer reaction time and lower accuracy was observed. (2) This study didn't show the expected class concept hierarchical direction effect. Specifically, there were no significant differences between the upper class concept masking the lower class concept and the lower class concept masks the upper class concept, only the basic level class concept masking superordinate level class concept had shorter response time and higher correct rate than superordinate level class concept masking basic level class concept. (3) The superordinate level class concept showed a certain processing advantage, that is, when the superordinate level class concept was used as masking word, it had better masking effect, with the longest response time and highest correct rate. The results of Experiment 2 were as follows:(1) For action results, when the target word was the subordinate level class concept, to take the subordinate, basic and superordinate level class concept as masking words, the use of subordinate level class concept masking subordinate level class concept had the longest reaction time and lowest accuracy, indicating that the masking effect was the best at this time, and recognition of the subject for the target word was the most difficult one. (2) For the EEG results, the main effects of the three experimental conditions were different reamarkably only at 300-400ms time window, when the target word and priming word were the same. In particular, the subordinate level class concept masking subordinate level class concept would produce more positive amplitude than the basic level class concept masking subordinate level concept and the superordinate level class concept masking subordinate level class concept, while there was no significant difference in the amplitude induced by the basic level class concept masking subordinate level class concept and the superordinate level class concept masking subordinate level class concept.The second part consists of Experiment 3, aiming to examine the recognition and neural mechanisms of hierarchical relationship between class concepts using "semantic priming tas k ". In this task, different levels of class concept were used as priming words and target words, successively presenting priming words and target words, the subjects were asked to judge whether target words belong to life categories. The present study aimed to discuss different class concept hierarchical relationships for the subject's behavioral responses and EEG responses in the semantic priming task, by manipulating class concept hierarchical relationship between the priming word and target words. Results were as follows:(1) The class concept hierarchical distance between priming words and target words had different impacts on the semantic priming effect, that is, the closer the class concept hierarchy, the better the priming effect, perhaps because of the higher "mental representation coincidence degree"; the easier the subject on the target words, the longer reaction time was obversed.(2) The subordinate level class concept had better effect on the superordinate level class concept, the priming from bottom to top had shorter reaction time and higher accuracy than the priming from top to bottom, which indicated that the semantic priming between class concept hierarchies had direction. (3) The superordinate level class concept showed a certain processing advantage, that is, when the superordinate level class concept was used as target word, it had the shortest response time and highest correct rate for the subject.(4) EEG results showed that, when the class concept hierarchical relationship between target word and start word was further, the more negative N400 amplitude was induced. When the subordinate class concept and superordinate class concept were target words, the class concept hierarchical distance effect just showed in N400 amplitude, nevertheless, when basic level class concept was target word, class hierarchical distance effect failed to be reflected.The third part consists of Experiment 4, aiming to examine the recognition and neural mechanisms of hierarchical relationship between class concepts using "category-based reasoning task". In this task, different levels of class concept were used as premises and conclusion items, successively presenting premise and conclusion items, the subjects were required to judge the possibility degree of sharing some attribution by conclusion items and premises. This research aimed to change the class concept hierarchical relationship between premises and conclusion items systematically, in an attempt to examine the cognitive and neural mechanisms of different class concept hierarchical relationships in category-based reasoning task. Results were as follows:(1) The class concept hierarchical distance between premise and conclusion items had different effects on the category-based reasoning effect, that is, the closer the class concept hierarchy, the easier the subject make judgment on the conclusion item,the shorter reaction time and higher affirmative judgment ratio was observed.(2) The reasoning from top to bottom (deductive inference) had shorter reaction time and higher affirmative judgment than the reasoning from bottom to top (inductive inference), which indicated that the category-based reasoning between class concept hierarchy had direction. (3) The basic level class concept showed a certain processing advantage, indicating no matter whether basic level class concept was premises or conclusion items, it had the shortest response time and highest affirmative judgment rate.(4) EEG results showed that, when the class concept hierarchical relationship between premised or conclusion items was farther, the more negative ERP amplitude was induced at 250-450ms time window.To sum up, different class concept hierarchical relationships affected the performance of subjects in the semantic masking, semantic priming, and class reasoning task, reflecting by behavioral data and EEG data, whether class concept hierarchical relationship is specific for relatively simple word recognition activity or relatively complex class confirmation activity or more complex reasoning activities, it had an impact. However, due to different requirements for each task, even with the same set of materials, the impact of class concept hierarchical relationships may be not fully similar. Taken together, the following conclusions could be drawn in this research:(1) Preference processing features between the class concept hierarchies will be affected by different task paradigms. In this study, even using the same set of experimental materials in three tasks, the processing advantages among class concept hierarchies in the three tasks had different performance, showing that the task difference is a factor that leads to preference processing debate between the class concept hierarchies. Different task requirements will affect the extraction of class concept representation and integration of different class concept relations, thus affecting subjects'responses.(2) Differences of cognition processing of different class concept hierarchies are presented mainly through the distance effect and direction effect. Distance effect is reflected in two aspects:First, among different levels of hierarchical relationships, the hierarchical distance between subordinateand basic level class concept is the minimum, followed by the distance between basic and superordinate level class concepts, while the hierarchical distance between subordinate and superordinate level class concepts is the maximum. Second, within the same level of hierarchical relationship, hierarchical distance between subordinate and subordinateclass concept is smaller than that between basic and basic level class concepts. Further speaking, the different class concept hierarchical distance will lead to the feature duplication numbers difference of both class concepts ("Mental representation coincidence degree"), the smaller the class concept hierarchical distance, the greater the "Mental representation coincidence degree". On the contrary, the greater the class concept hierarchical distances, the smaller the "Mental representation coincidence degree". Different "Mental representation coincidence degree" can affect subjects'performances in tasks based on class concept hierarchical relationship, due to different requirements for these tasks. Performance of action results is also different, but the EEG results patterm is relatively consistent, that is, the greater the class concept hierarchical distance, the more negative N400 amplitude was induced, the EEG composition is related to the integration processes of class concept hierarchical relationship. Direction effect means that the completion of three tasks needs the integration of hierarchical relationships between both class concepts. In one kind of class concept hierarchical relationship, two different directions ("from bottom to top" and "from top to bottom ") will be generated. Because of the difference of the three different tasks themselves in the study, the direction effects of class concept hierarchical relationships have their own characteristics and keep inconsistent.(3)Based on this study, we propose a model on class concept hierarchy processing termed "mixed reaction model of class concept processing", in an attempt to more accurately predict and explain phenomena in class concept hierarchical processing. In this model, the hierarchical processing of the class concept is divided into two processes (processing and reaction), and three stages (perception, representation and output).