Living on the edge: strategic and instructed slowing in the stop signal task.

The stop signal task is widely adopted to assess motor inhibition performance in both clinical and non-clinical populations. Several recent studies explored the influence of strategic approaches to the task. In particular, response slowing seems to be a strategic approach commonly adopted to perform the task. In the present study, we compared a standard version with a strategic version of the task, in which participants were explicitly instructed to slow down responses. Results showed that the instructed slowing did not affect the main inhibition measure, thus confirming the robustness of the stop signal index. On the other hand, it apparently changed the nature of the task, as shown by the lack of correlation between the standard and the strategic versions. In addition, we found a specific influence of individual characteristics on slowing strategies. In the standard version, adherence to task instructions was positively correlated with compliant traits of personality. Despite instructions to maximize response speed, non-compliant participants preferred to adopt a slowing strategy in the standard version of the task, up to a speed level similar to the strategic version, where slowing was required by task instructions. Understanding the role of individual approach to the task seems to be crucial to properly identify how participants cope with task instructions.