| In daily life, we need to select the desired information from hundreds of thousands of mass information and ignore irrelevant information becasuse of a limited processing system. Subsequently, the ignored material is subject to impaired processing. That is, one may have a slower reaction time or less accurate responding to previously ignored objects than to a new object. This phenomenon is known as negative priming (NP). A typical NP experiment often involves two consecutive displays labeled "prime" and "probe". In each display, targets and distractors are included, and the targets in probe display are identical or related to the distractors in prime display. Participants are asked to response to the targets in each display.It is generally believed that the presence of selective conditions in prime display leads to the occurrence of negative priming. However, some recent studies have shown that when the prime display consists of a single word (no choice and ignore), NP can also be triggered by manipulating some other conditions (e.g. the proportion of repeated trials, ignore instructions, consciousness of the primes, prime-target SOA), which challenges the traditional view on selective inhibition.The above-mentioned conditions suggest that it seems the top-down inhibitory mechanisms (expectation or ignored language) play a key role in triggering the negative priming. However, there are some obvious deficiencies in previous studies to explore this mechanism:it is unknown whether the expected strategies can play a role in manipulating the proportion of related trials in single-prime and only target paradigm; these ideas on the long enough prime-target SOA helpful to information of inhibition can not explain all of the relevant researches; when a brief prime is followed immediately by a pattern mask, the role on the top-down strategy (ignore instruction) in triggering single-prime NP has not been clarified. In current study, the materials of Chinese charaters are used, and participants are required to make a binary animate/inanimate judgment on a single target that was preceded by a semantically related or unrelated prime. We explore the influence of the top-down inhibitory process resulting from the expectation on the negative priming underlying the proportion of related trials in single-prime and only target paradigm; and verify the crucial role of the blank interval (ISI) between prime and mask or between mask and target in inhibitory formation with the constant prime-target SOA; and then examine the relative role of the bottom-up (triggered by ignore instruction) and top-down (resulted from mask) inhibition when ISI is located between mask and target.This study contains a series of ten experiments for three parts.The first part, using the single-prime and only target paradigm, manipulates the proportion of related trials which is less concerned previously and increases the quantity of the stimuli set, and then explores the features of the top-down inhibitory mechanism from expectations. It contains two experiments. In Experiment1, the proportion of related trials is set to20%and80%. Semantic negative priming effect is observed in20%condition, whereas the reliable positive priming effect is observed in80%. In Experimnet2, we manipulates further the quantity of the stimuli set based on the low proportion of related trials, and finds that only the small stimuli set can induce a reliable negative priming.The second part focuses on the influence of interstimulus intervals (ISIs) between prime and mask or between mask and target on inhibitory formation in the constant prime-target SOA conditions. It consists of five experiments, In all five experiments, a brief (16ms) and ignored single prime appeared at center, and followed by a mask (##), and then a single target appeared which entailed semantic categorization. An ISI could be inserted either between the prime and mask (Experiment3and7) or between the mask and target (Experiments4-6). The objective of Experiment3is to examine whether it is more conducive to the formation of inhibition when a blank interval (470ms prime-mask ISI) is inserted between prime and mask than no interval (0ms prime-mask ISI), thus triggering the negative priming effect. The results show that a significant negative priming effect is observed by inserting ISI, whereas a reliable positive priming effect is found without ISI. Experiment4is to examine whether the same interval as that between prime and mask in Experiment3inserted between mask and target (470ms mask-target ISI) is similarly more benificial to triggering negative priming than without ISI (0ms mask-target ISI). As the results, attenuation of activation is found in470-ms ISI condition, whereas the reliable PP is found in0-ms ISI as that in Experiment3. Experiment5focuses on whether prolonged mask-target ISI (700ms) is more conducive to trigger negative priming than short mask-target ISI (470ms). The results show that a significant negative priming effect is found in the long ISI, while the same pattern of result as that of Experiment4is observed. To verify the negative priming in long mask-target ISI condition is indeed caused by the lengthened ISI, rather than by the corresponding lengthened pime-target SOA, Experiment6continues to use the long mask-target ISI in Experiment5(In order to compare with the other condition in current experiment, it was called as the114-ms mask/700-ms blank) and compared it with the short mask-target ISI (700-ms mask/114-ms blank). It is found that a significant negative priming effect in the former condition as that of Experiment5, while does not in the latter. Because the results in Experiment3-6demonstrate that either ISI inserted between prime and mask or between mask and target, can lead to negative priming effect, just that shorter duration is required for the latter, Experiment7manipulates the variable length of prime-mask ISI (70ms,170ms,470ms) and explores whether negative priming can be observed in the shorter length of prime-mask ISI. The result is that NP is found only in470-ms prime-mask ISI condition as that of Experiment3.The third part explores whether the inhibitory effect is caused exactly by the top-down ignore instruction or the bottom-up mask when ISI is located between mask and target. In other words, that is to examine the relative role of these two inhibitions in triggering negative priming effect. This part is composed of three experiments. Experiment8continues to use the masking "##" as that of the second part without ignore instruction, and explores whether negative priming can only occur in weak activation of prime. A significant NP is observed in long ISI condition. But the result can not rule out that the inhibitory formation is affected by the ignore stratigies used by participants themselves. Experiment9uses a masking stimuli of greater density ("2") without ignore instruction too, and explores what is the pattern of results when prime is unconscious without ignore instruction. Non-significant negative priming is observed in two ISIs. Experiment10still uses "(?)" as a masking stimulus and compares the inhibitory effect both with and without ignore instruction. Only a significant NP is observed when there is ignore instruction.According to the study results above, we make conclusion as below:1. When the proportion of related trials is manipulated in single prime and only target paradigm, the inhibitory effects indeed result from the top-down expected strategies, instead of the default effect previously thought. Nevertheless, the implementation of inhibition relates to the size of stimuli set. Smaller stimulus set can trigger a greater inhibition, while the larger stimulus set can induce lower, or even can not induce it. This relates to the salience of prime’ feature caused by different sizes of stimulus set.2. Formation of inhibition depends on the length of ISI between prime and mask or between mask and target. But the required length of ISI is shorter when it is located prime and mask (strong activation) than between mask and target (weak activation). This supports our proposed viewpoints that long enough ISI is a prerequisite for the formation of inhibition, and that the remained existence of other interference information (prime or mask) will occupy cognitive resources and affect the implementation of inhibition. Simultaneously, this result also supports the viewpoints that the speed of inhibitory formation is faster when prime word is activated stronger than weaker.3. When ISI is located between mask and target, the inhibitory effect comes from the top-down ignore instruction. Unconscious masking strategy alone can not lead to NP, instead that NP is triggered by adding a top-down ignore instruction in unconscious condition. |
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