The salience of the stop signal affects triggering and latency of response inhibition across species: findings from a Bayesian approach

Inhibitory control is the ability to suppress an ongoing response and can be assessed using the Stop Signal Task. In this task, participants respond as quickly as possible to a go signal, but on a minority of trials, a stop signal appears after the go signal, requiring inhibition. In the Stop Signal Task, response inhibition is measured by the Stop Signal Reaction Time (SSRT), which reflects the latency of the inhibitory process. The visual salience of the stop signal can influence SSRT. However, it remains unclear whether visual salience also affects the ability to trigger the inhibitory process. Indeed, classical methods for estimating SSRT do not account for trigger failures, that is, trials in which the inhibitory process is not triggered. As a result, SSRT estimates may be inflated and furthermore it remains unclear whether observed effects reflect changes in inhibitory latency or differences in the ability of triggering the inhibitory process. To address this issue in the context of salience effects, we applied a Bayesian model that estimates SSRT independently of trigger failures and also computes their probability on humans and monkey data. We found that a more salient stop signal led to a faster SSRT and easier triggering of inhibition (lower probability of trigger failure), highlighting the importance of stop signal detection in response inhibition. Furthermore, this effect was consistent across species, suggesting that non-human primates provide a valuable model for studying the neural basis of inhibitory control.