Signal-related contributions to stopping-interference effects in selective response inhibition

In our ability to selectively inhibit a subset of concurrent response tendencies, referred to as selective response inhibition, stopping-interference (SI) effects have been found and attributed to global inhibitory processes. In the standard stop-signal paradigm, the stop signal might not only signal stopping but also produce other effects simply by virtue of being an additional signal. Therefore, we investigated whether previously observed SI effects reflect not only selective response inhibition but also other effects caused by the appearance of the stop signal. In Experiment 1, we controlled for the possible extra influences of the stop signal and still found SI effects, allowing a more confident attribution of SI effects to global inhibitory processes. Furthermore, the extra signal affected the motor system, as revealed by a reduction in SI effects on response force after the improved control. Using the lateralized readiness potential, Experiment 2 showed that the extra signal affected relatively central motor processing. The findings thus advance our knowledge about the distinction between signal-related and motor-inhibitory effects in stop-signal tasks.