Reaction Time Interval And Task Difficulty Affect Consistency Sequence Effect

The environment is usually brimming with multiple sources of potentially relevant and useless information. Limited processing capacity of the visual system decide that there is impossible and no need to process all external information. A fundamental ability of the cognitive system is to maintain current goal representations in the face of distraction. Selective attention enables us to select task-relevant stimulus features while suppressing distracting information, alternative goals, and competing response tendencies. Selective attention plays an active role in maintaining and organizing mental activity, and it can also help human to adapt to the environment.Congruency sequence effects are a special phenomenon of selective attention. Congruency sequence effects refer to the phenomenon that congruency effects (conflict effects) depend on the congruency of the preceding trial. When the previous trial is incongruent, the congruency effects (conflict effects) will be weaker than for a previous trial which is congruent. By studying the congruency sequence effects in different tasks with kinds of stimuli, researchers study the mechanism of the effect. However, there has been a heated debate on the mechanism of congruency sequence effects. There are two main views:conflict monitoring hypothesis and feature integration account. The conflict monitoring hypothesis assumes that this sequential modulation is based on top-down cognitive control and suggests that more control is engaged after the detection of conflict. An increase in cognitive control is thought to result in stronger attentional biasing of information processing in line with current task. This interpretation of the congruency sequence effects has been termed conflict adaptation effects. The feature integration account explains the congruency sequence effects can be attributed to the operation of a feature-integration process without requiring top-down regulation. This feature-integration process will result in binding of features of the stimulus-response episode into a representation which is termed an event file. When some but not all features of the stimulus-response episode repeat from the previous trial, the repeating features automatically activate other features in the event file from the previous trial. These activated features compete with the current features and lead to longer RTs. When every feature repeats or alternates, there is no such problem, because no competing features are activated. This interpretation of the congruency sequence effects has been termed feature integration effects. In general, at least to some extent, congruency sequence effects can be attributed to bottom-up repetition effects. Which theory can better explain the mechanism of congruency sequence effects? The purpose of the current research was to investigate the temporal aspects of top-down conflict monitoring and bottom-up feature integration.To investigate the temporal aspects of top-down conflict monitoring and bottom-up feature integration, three experiments were conducted. In Experiments1-3, we used a Flanker task in which four different letters, mapped onto four response keys, could occur as targets and flankers. In Experiment1, we investigated the top-down and bottom-up sequential modulations with different RSIs. In the all RSIs conditions, a reduced Flanker effect after incongruent trials was obtained in the repetition trials. However, for complete alternation trials, sequential modulation of the Flanker effect was observed only in the200-ms interval condition. When the response-stimulus interval was50ms,200ms,750ms,1000ms,1500ms and3000ms, the sequential modulation of the Flanker effect was not observed. These results suggest that the top-down and bottom-up sequential modulations respectively contribute to the congruency sequence effects. More important, top-down sequential modulation may be sensitive to RSI. The aim of Experiment2was to investigate whether task demands could affect top-down sequential modulation mechanism. More specifically, we investigated the top-down control whether could be evoked by increasing task demands. The results showed congruency sequence effects occurred both in complete alternation trials and repetition trials when the response-stimulus interval was1500ms. The results suggest that adjustments of cognitive control are not only also sensitive to RSI, but also depend on task demands. The aim of Experiment3was to explore whether top-down control would disappear by decreasing task demand. More specifically, we investigated whether the congruency sequence effects could vanish in the complete alternation trials by decreasing task demands with200-ms interval. The results showed congruency sequence effects disappeared in complete alternation trials but persisted in repetition trials. The results of Experiment3are in good agreement with the results of Experiment2, which suggest the bottom-up sequential modulation is a basic lower level mechanism, and top-down control is a higher level mechanism and flexibly adjusted to task demands.In conclusion, we have shown that two modulatory sources can cause smaller congruency effects after incongruent trials. One process reflects top-down reconfiguration, which is triggered by the occurrence of conflict on an incongruent trial. Another source is a bottom-up process, caused by stimulus features and response features repetitions. More importantly, the bottom-up modulation may be a basic lower level mechanism, while the top-down control may act at a high level, being flexibly adjusted to RSI and task demands. In addition, the research has a certain reference value for the controversy that exists in previous studies...