Proactive and Reactive Response Inhibition across the Lifespan
All times in this figure are relative to the onset of the response window, which was 500 ms after the fruit started falling. The horse race model  assumes that a Stop process with fixed duration is set off as soon as the stop signal is presented. This process then catches up with the Go process only if the stop was initiated far enough in advance of the Go response. This might happen 1) if the Go process happened to be slow on that trial and/or 2) if the stop-signal was presented early. Confirming the first prediction, in stopFail trials (where the subject erroneously responds and thus fails to stop) the reaction times are on average faster than in Go trials, in both the Unprepared (A) and Prepared (B) condition. Confirming the second prediction, the later the stop-signal was presented (i.e. the later the fruit turned brown) the lower the chance of stopping successfully (C). Lastly, if the stop signal is presented close to the onset of the response window then the Stop process cannot catch up even with slow Go responses; this predicts that the average stopFail RT will go up with later stop signals, which is indeed the case (D). Error bars indicate 95% confidence intervals. White dots in A and B indicate population means.