The Mechanism Of Self - Inhibition Of Negative Correlation Between The Object Level And The Response Level

The classical negative compatibility effect (NCE) is that viewers’responses to the targets show faster RTs and fewer errors when those targets are preceded by incompatible primes (i.e., cueing opposite responses to the targets), but delayed responses and more errors are observed if targets are preceded by compatible primes (i.e., cueing the same responses as the targets). The classical NCE paradigm presents a series of stimuli in sequence, containing prime, mask and target in which left or right pointing double arrows are used as primes and targets. The task requires participants to respond to the orientation of the target (left pointing arrow with left-hand response and right pointing arrow with right-hand response).The negative compatibility effect seems counterintuitive, and several hypotheses have been proposed to explain it. The most famous hypotheses contain the self-inhibition account and the object-updating account. The self-inhibition account hypothesizes that motor activation by a subliminal prime is automatic and produces an inhibition against the initial activation. In this view, inhibition occurs only if a mask terminates perceptual evidence of the prime and if the prime’s activation strength is sufficiently great that it triggers an inhibitory mechanism; the object updating account assumes that the NCE results from object-updating triggered by a perceptual interaction between prime and mask. It emphasizes that the NCE could only be observed with relevant mask (e.g., two overlaid opposite pointing double arrows). Furthermore, some researchers neutralize these two accounts and suggest that the NCE might originate from both object-updating and self-inhibition processes. However, there are three issues about these NCE accounts:1) whether object-updating and self-inhibition both play roles in producing the NCE. Two potentially influential factors are found in previous studies:these involve first, irrelevant masks (random vertical and horizontal lines) could not cease the perception of arrow primes, which may be lead to reduced NCE size. Second, relevant masks are not as relevant as in the classical NCE, which may be lead to ineffective object-updating;2) whether the object-updating related NCE originates from response code level. Odd number of response rule (e.g., only respond to left arrow) is often used to clarify this issue. However, these response rules may be violate the pre-condition of response code updating process, and thus the conclusion could not be suitable for explaining the classical NCE;3) whether the continuous or the threshold mechanisms dominate the self-inhibition triggered NCE. Two potentially influential factors are found in the previous studies. First, the strength of mask representation is smaller than that in the classical NCE paradigm, and thus object-updating account could give an alternative explanation for their results. In addition, the results might also be explained by the continuous mechanisms because the limited interval between mask and target. Second, primes are processed supraliminally in the study supporting the continuous mechanisms, which may be violate the precondition of self-inhibition, and could not directly query the threshold hypothesis.In order to investigate the above issues, the current study developed six experiments attaching to three series of research.The first study used novel type of numerical stimuli (comprising short lines of equal length, see figure2-1), in order to investigate whether object-updating and self-inhibition both play roles in producing the NCE. This type of stimuli could not only ensure that primes are effectively masked in the irrelevant mask condition, but also guarantee a completely relevant mask. Experiment1manipulated three within subject factors containing mask relevance (relevant versus irrelevant mask, in order to separate the processing levels of the NCE into object-updating and self-inhibition), prime/target compatibility (compatible versus incompatible) and three successive days (day1, day2, day3) in order to enhance the links between stimuli and reactions. In addition, Experiment1was blocked by the two levels of mask relevance for the aim of accelerating participants’acquisition of the stimulus-reaction (S-R) links. Results showed that a significant NCE was observed only in the relevant mask condition in early day, but both significant NCEs were observed in the two mask conditions in latter days. Results indicated that the NCE originated from object-updating when the S-R links were weak, but originated from self-inhibition when the S-R links were acquired. Experiment2manipulated the similar factors as in the first experiment, except that two levels of mask relevance were presented randomly (with equal probability) over trials in both blocks (again with equal probability) in order to confirm that the results of Experiment1were reliable and unaffected by the expectancy effects. Results of Experiment2was similar to the first experiment, which indicated that block design did not affect the pattern of the NCE, but only accelerated the acquisition of the S-R links. Thus, the conclusion of Experiment1was reliable.The second study used Arabic numerals as primes and targets, in order to investigate whether the object updating related NCE not only originates from feature updating, but also derives from response code updating. These stimuli could help us to separate the object-updating related NCE into feature updating and response code updating in two alternative responses. Experiment3manipulated three within subject factors:mask relevance (feature and response code relevant mask versus only response code relevant mask, in order to separate feature updating and response code updating) together with prime and target compatibility (compatible versus incompatible) that extended over three successive days (day1, day2, day3, again, in order to enhance the S-R links). Furthermore, a special rule (i.e., two alternative finger responses in right hand) was performed in order to diminish the impact of motor inhibition, and confirmed the effectiveness of the response code updating. Results showed that significant NCEs emerged only in the feature and response code relevant mask condition, but not in the other throughout three-day practice. Results indicated that the object updating related NCE only originates from feature updating. Experiment4was used to exclude an alternative explanation of Experiment3, that is, the S-R links might not be familiar enough to automatically encode the digits. Accordingly, Experiment4manipulated the same factors as Experiment3, but two-hand responses were performed to enhance the impact of the motor inhibition. Results showed that a significant NCE emerged in the only response code relevant mask condition in late day, which confirmed three-day practice was long enough to acquire the S-R links. Consequently, the conclusion of Experiment3was reliable.The third study used event related potential to investigate the inhibitory mechanisms of the NCE. The study imitated the paradigm, which has been used to support the inhibitory threshold hypothesis, but with some improvements. First, the strength of mask representation was controlled similar to the classical NCE; second, two different irrelevant masks were presented in succession in each trial to guarantee a subliminal inhibitory circumstance and meanwhile to reduce effectiveness of object-updating. Experiment5manipulated two within subject factors, containing prime/target compatibility (compatible versus incompatible) and density of prime background (0%,25%,50%, in order to reduce prime activation strength). Results showed that a significant NCE emerged in the0%density condition, but disappeared in the25%and50%density conditions. Results indicated that the NCE disappeared along with attenuated prime activation. This was supported by both the continuous subliminal inhibitory mechanisms and the inhibitory threshold hypotheses. Experiment6fixed the prime’s background at the density of25%, and manipulated ISI between mask and target (150ms,250ms,350ms) as well as prime/target compatibility to further test these two hypotheses. The behavioral results showed a marginally significant NCE in the150ms ISI condition. The electrophysiological results also showed that the lateralized readiness potential for compatible trials was significantly more positive than that for incompatible trials in the150ms ISI condition. In addition, the NCE size was significant smaller in Experiment6than in Experiment5. All of the above results favored the continuous subliminal inhibitory mechanisms hypothesis, that is, when the strength of the prime activation decreases, the following inhibitory process experiences time delays and substantial declines in strength.According to the results of the three studies, we concluded that:1. Object-updating in perceptual level and self-inhibition in response level can both contribute to the NCE. If the strength of the prime stimulus and response link is too weak to trigger the following inhibition, the object-updating in perceptual level make a greater contribution to the NCE; if the strength of the links is reinforced by practice, which exceeds the inhibitory threshold, both processing levels make contributions to the NCE, but self-inhibition in response level is primarily responsible.2. The object updating related NCE may primarily originate from the feature updating in the perceptual level rather than from the response code updating in the response level.3. The self-inhibition triggered NCE may be dominated by a continuous subliminal inhibitory mechanism rather than a threshold mechanism.