To respond or not to respond? A model-based comparison between the processing of go, nogo, and neutral stimuli.

We analyzed the processing of go, nogo, and neutral stimuli by means of the interactions that arise when two stimuli are presented in temporal proximity. In Experiment 1, we tested four leaky, competing accumulator models of a flanker task with go and nogo targets and go, nogo, and neutral flankers. The models differed in whether they included a nogo-response code and thus a covert nogo response or not. Nogo flankers produced similar response conflict as incompatible go flankers, supporting a model with a nogo-response code. The best-fitting model had higher thresholds for nogo than for go responses and stronger lateral-inhibition gain between go-response and nogo-response codes than between go-response codes. We further explored the validity of the models by testing their predicted sequential effects in Experiments 2A and 2B. Consistent with the best-fitting model, RTs to a go signal were longer after a nogo signal than after a (different) go signal when the stimulus onset asynchrony (SOA) was long enough for responses to first signals (i.e., ≥ 1 s). However, when the SOA was too short for first-signal responses (i.e., ≤ 0.5 s) this difference was slightly reversed. This pattern of results was consistent with predictions of the best-fitting model after a change of the lateral-inhibition gain. We conclude that nogo stimuli and go stimuli are processed in qualitatively the same way and different from neutral stimuli but may differ in quantitative and strategically adjustable processing characteristics such as response thresholds and lateral inhibition. (PsycInfo Database Record (c) 2020 APA, all rights reserved).