从字形到语义：跨语言Stroop效应的ERP研究

According to the influential dual-route model of reading (Coltheart, Rastle et al. 2001), there are two routes to access the meaning of visual words: one directly by orthography (orthography-semantic) and the other indirectly via the phonology (phonology-semantic). Because of the dramatic difference between written Chinese and alphabetical languages, it is still on debate whether Chinese readers have the same semantic activation processes as readers of alphabetical languages. In this study, the semantic activation processes in alphabetical German and logographic Chinese were compared. Since the N450 for incongruent color words in the Stroop tasks was induced by the semantic conflict between the meaning of the incongruent color words and color naming, this component could be taken as an index for semantic activation of incongruent color words in Stroop tasks. Two cross-script Stroop experiments were adopted to investigate the semantic activation processes in Chinese and German. The first experiment focused on the the role of phonology, while the second one focused on the realative importance of orthography. Cultural differences in cognitive processing between individuals in western and eastern countries have been found (Nisbett & Miyamoto, 2005). In order to exclude potential differences in basic cognitive processes like visual discrimination capabilities during reading, a visual Oddball experiment with non-lexical materials was conducted with all participants. However, as indicated by the P300 elicited by deviant stimuli in both groups, no group difference was observed. In the first Stroop experiments, color words (e.g., “green”), color-word associates (e.g., “grass”), and homophones of color words were used. These words were embedded into color patches with either congruent color (e.g. word “green” in green color patch) or incongruent colors (e.g. word “green” in either red or yellow or blue color patch). The key point is to observe whether homophones in both languages could induce similar behavioral and ERP Stroop effects to that induced by color words. It was also interesting to observe to which extent the N450 was related to the semantic conflicts. Nineteen Chinese adult readers and twenty German adult readers were asked to respond to the back color of these words in the Stroop experiment in their native languages by pressing the corresponding keys. In the behavioral data, incongruent conditions (incongruent color words, incongruent color-word associates, incongruent homophones) had significantly longer reaction times as compared to corresponding congruent conditions. All incongruent conditions in the Geman group elicited an N450 in the 400 to 500 ms time window. In the Chinese group, the N450 in the same time window was also observed for the incongruent color words and incongruent color-word associates. These results indicated that the N450 was very sensitive to semantic conflict-even words with semantic association to colors (e.g. “grass”) could elicite similar N450. However, the N450 was absent for incongruent homophones of color words in the Chinese group. Instead, in a later time window (600-800 ms), incongruent homophones elicited a positivity over left posterior regions as compared to congruent homophones. Similar positivity was also observed for color words in the 700 to 1000 ms time window in the Chinese group and 600 to 1000 ms time window for incongruent color words and homophones in the Geman group. These results indicate that phonology plays an important role in Geman semantic activation processes, but not in Chinese. In the second Stroop experiment, color words and pseudowords which had similiar visual shape to color words in both languages were used as materials. Another group of eighteen Chinese and twenty Germans were involved in the Stroop experiment in their native languages.The ERPs were recorded during their performance. In the behavioral data, strong and comparable Stroop effects (as counted by substract the reaction times in the congruent conditions from reaction times in the incongruent conditions) were observed. In the ERP data, both incongruent color words and incongruent pseudowords elicited an N450 over the whole brain scalp in both groups. These results indicated that orthography played an equally important role in semantic activation processes in both languages. The results of the two Stroop experiments support the view that the semantic activation process in Chiense readers differs significantly from that in German readers. The former rely mainly on the direct route (orthography-semantic), while the latter use both direct route and incirect route (phonology-semantic). These findings also indicate that the characteritics of different languages shape the semantic activation processes.

海洛因成瘾者决策障碍及其行为机制的研究----短视行为及冲动、强迫和药物在决策中的作用

Addiction can be investigated from the perspective of decision making. Addicts usually make incorrect decisions when facing drug-related cues or they are driven to drugs, resulting in repeated drug seeking and taking. The present study adopted temporal discounting as behavioral task and on the basis of the fact that heroin addicts discounted more steeply than health participants (addicts preferred to choose immediate but smaller reward, regarded as myopia) which was consistent with previous research, three questions was raised and being concentrated on in this study. The first question was whether the character of myopia would be revealed in a somewhat complicated task? We designed a card game in which the participants were tested whether they would play the trump card in order to win a trick but not the whole game. Addicts played the trump card significantly earlier than controls did, indicating they focused on immediate single trick but not the game. Moreover, the performance in the card game and temporal discounting correlated significantly, suggesting addicts would display myopic decision not only in simply task like temporal discounting but also in task more complicated and similar to daily-life decision. Secondly, the present study adopted various kinds of temporal discounting tasks. In previous research, temporal discounting gain task was usually adopted. In the present study, we also adopted temporal discounting loss task. In either gain or loss task, there are two delayed amounts. Results showed in each decision condition addicts made poorer performance compared with control but in larger amount condition, addicts actually improved their decision performance. Meanwhile, addicts did not show loss aversion due to their close discount rates in gain and loss task while for controls, the discount rates were much lower in loss task than those in gain task. Thus we demonstrated that addicts were insensitive to negative outcomes by the method of temporal discounting. Finally, we investigated three mechanisms which exerted impacts on decision making. We adopted Go/NoGo task to test impulsivity and found addicts commits more errors (higher impulsivity) than controls did. We also designed a behavioral task which could be used to test drug-related compulsive behavior on human participants. Results showed addicts produced stereotyped key-pressing behavior when presented with drug-related cues. Furthermore, it was found participants with higher impulsivity displayed poorer performance in decision making but addicts with higher compulsivity only made poorer performance in smaller amount decision and the correlation between compulsivity and decision making was relative weak. In order to investigate the role of susceptibility and effect of drugs, we adopted years of abusing heroin as the indictor and discovered addicts with longer history of heroin abusing made poorer performance in smaller amount condition than addicts with shorter history. Also, the earlier the addicts began to use drug, the worse they would do in the smaller amount decision. The results here indicated drug itself could exert impact on decision making in certain condition. The present study revealed three characters of heroin addicts from the aspect of decision making: (1) focusing upon current benefit due to they preferred to choose immediate gain and delayed loss; (2) showed no loss aversion compared with healthy participants (3) inability to inhibit inappropriate response particularly when facing drug-related cue. These characters contribute to the facts that addicts seek and take drugs repeatedly while ignoring the negative consequences caused by abusing drugs.