Fini Chiara, Fischer Maja, Bardi Lara, Brass Marcel, Moors Agnes
Department of Dynamic and Clinical Psychology, University of Rome La Sapienza, Rome, Italy.
Research Group of Quantitative Psychology and Individual Differences, KU Leuven, Leuven, Belgium; Centre for Social and Cultural Psychology, KU Leuven, Leuven, Belgium.
Neuropsychologia. 2020 Jun;143:107496. doi: 10.1016/j.neuropsychologia.2020.107496. Epub 2020 May 12.
Previous behavioral studies using stimulus-response compatibility tasks have shown that people are faster to carry out instructed approach/avoidance responses to positive/negative stimuli. This result has been taken as evidence that positive/negative stimulus valence directly activates a tendency to approach/avoid, which in turn, facilitates execution of instructed approach/avoidance behavior. In these studies, however, it cannot be excluded that the results reflect a purely semantic link between stimulus valence and instructed responses. According to this alternative interpretation, positive/negative stimuli do not elicit an approach/avoidance tendency, but instead they interact with the positive/negative valence of the instructed responses, and in this way, produce the observed compatibility effect. To circumvent this possible disadvantage of compatibility tasks, we used a novel method for the measurement of early action tendencies: TMS induced MEPs. In two experiments, participants were first trained to abduct the index finger to approach and the thumb to avoid. Then, they observed a series of positive and negative stimuli. Each stimulus was followed by a TMS pulse (at 400 ms post-stimulus onset) and MEPs were measured continuously on the muscles of both fingers. These observation trials were randomly intermixed with response trials, in which neutral stimuli were presented and participants were instructed to approach/avoid the stimuli. In Experiment 1, participants received clear visual feedback on the outcome of their response in the response trials. In Experiment 2, we omitted this feedback to test whether it was necessary for the effect to occur. The results indicated higher MEPs for the approach/avoidance finger after positive/negative stimuli in Experiment 1 but not in Experiment 2. Analyses on the data aggregated over both experiments suggest that the visual feedback was necessary for stimulus valence to elicit action tendencies. Taken together, the results are in line with the results of behavioral studies with compatibility tasks, suggesting that stimulus valence directly elicits specific action tendencies already at 400 ms but they indicate that clear visual feedback is necessary for this effect to occur.
以往使用刺激-反应兼容性任务的行为研究表明，人们对正性/负性刺激执行指示性的趋近/回避反应时速度更快。这一结果被视为正性/负性刺激效价直接激活趋近/回避倾向的证据，进而促进指示性趋近/回避行为的执行。然而，在这些研究中，不能排除结果反映的是刺激效价与指示性反应之间纯粹的语义联系。根据这种替代性解释，正性/负性刺激不会引发趋近/回避倾向，而是与指示性反应的正性/负性效价相互作用，从而产生观察到的兼容性效应。为了规避兼容性任务的这一潜在缺陷，我们采用了一种测量早期行动倾向的新方法：经颅磁刺激诱发的运动诱发电位。在两项实验中，参与者首先接受训练，食指外展表示趋近，拇指外展表示回避。然后，他们观察一系列正性和负性刺激。每个刺激之后都有一个经颅磁刺激脉冲（在刺激开始后400毫秒），并持续测量两根手指肌肉上的运动诱发电位。这些观察试验与反应试验随机混合，在反应试验中呈现中性刺激，并指示参与者趋近/回避这些刺激。在实验1中，参与者在反应试验中会收到关于其反应结果的清晰视觉反馈。在实验2中，我们省略了这种反馈，以测试这种反馈对于产生该效应是否必要。结果表明，在实验1中，正性/负性刺激后，趋近/回避手指的运动诱发电位较高，而在实验2中则不然。对两项实验汇总数据的分析表明，视觉反馈对于刺激效价引发行动倾向是必要的。综合来看，这些结果与兼容性任务的行为研究结果一致，表明刺激效价在400毫秒时就直接引发特定的行动倾向，但也表明这种效应的发生需要清晰的视觉反馈。
