Vation of the stop response or stopping network (Verbruggen, McLaren, Chambers,Author Manuscript Author Manuscript Author Manuscript Author ManuscriptCognition. Author manuscript; available in PMC 2016 April 08.Verbruggen and LoganPage2014). In selective stop tasks, the selection can be quite difficult, especially when the signal mapping constantly changes. By contrast, in stop-signal and stop hange tasks with only one signal, selection of the appropriate action is very straightforward. Consequently, stopping will not interfere much with the primary task. The idea that selection demands are low in standard stop-signal and stop hange tasks is also consistent with the idea that most of SSRT in these tasks is occupied by afferent or sensory processes (Boucher et al., 2007; Logan et al., 2014, 2015; Salinas Stanford, 2013). One could even speculate that stopping in standard stop-signal tasks is a `prepared reflex’ (e.g. Hommel, 2000; Logan, 1978; Meiran, Cole, Braver, 2012). Several studies indicate that goal-directed actions may not require much control anymore once the task instructions are properly implemented: `the components of the task seem automatic, but the task itself is not’ (Logan, 1978, p. 57). In stop tasks with only one signal, stopping could be a prepared reflex due to the low signal selection demands. Once the task instructions are implemented (`IF signal THEN stop’), the stop process can be triggered easily by the presentation of the stop signal; consequently, stop processing and AZD4547MedChemExpress AZD4547 rule-based (or algorithmic) primary-task processing can occur in parallel without much dual-task interference (cf. Kahneman, 2003; Logan, 1979, 1988; Schneider Shiffrin, 1977; Shiffrin Schneider, 1977). We should point that capacity sharing can occur in stop-signal tasks with a single stop signal. The stop rate parameters depend on the discriminability, intensity, and modality of the stop signal (e.g. van der Schoot, Licht, Horsley, Sergeant, 2005), which could be interpreted as a capacity limitation (Logan et al., 2014). Furthermore, we have recently demonstrated that competition between visual signals in the go and the stop tasks influences stopping (Verbruggen, Stevens, Chambers, 2014), which is consistent with the idea that stimuli have to Tasigna chemical information compete for limited processing capacity. Thus, it seems that under certain circumstances, capacity sharing may also occur in simple stop-signal tasks. 3.4. Categorically different stopping strategies? Maybe not Our results are very similar to those observed in previous selective stop studies. As discussed above, two main selective stopping strategies have been proposed in this literature: the `Stop then Discriminate’ strategy (also know as the `Stop-Restart’ strategy; e.g. Aron, Behrens, Smith, Frank, Poldrack, 2007) and the `Discriminate then Stop’ strategy. To distinguish between these two strategies, researchers have relied on differences between nosignal RTs, signal espond RTs, and invalid-signal RTs. But our analysis indicates that such RT differences could be due to capacity sharing and the difficulty of the discrimination process. In other words, our study indicates that RT differences between the groups, subjects, or conditions in selective stop tasks could be quantitative (i.e. degree of capacity sharing) rather than qualitative (i.e. different strategies). This is not to say that strategies have no role in selective stop tasks. Many studies indicate that people use various strategies.Vation of the stop response or stopping network (Verbruggen, McLaren, Chambers,Author Manuscript Author Manuscript Author Manuscript Author ManuscriptCognition. Author manuscript; available in PMC 2016 April 08.Verbruggen and LoganPage2014). In selective stop tasks, the selection can be quite difficult, especially when the signal mapping constantly changes. By contrast, in stop-signal and stop hange tasks with only one signal, selection of the appropriate action is very straightforward. Consequently, stopping will not interfere much with the primary task. The idea that selection demands are low in standard stop-signal and stop hange tasks is also consistent with the idea that most of SSRT in these tasks is occupied by afferent or sensory processes (Boucher et al., 2007; Logan et al., 2014, 2015; Salinas Stanford, 2013). One could even speculate that stopping in standard stop-signal tasks is a `prepared reflex’ (e.g. Hommel, 2000; Logan, 1978; Meiran, Cole, Braver, 2012). Several studies indicate that goal-directed actions may not require much control anymore once the task instructions are properly implemented: `the components of the task seem automatic, but the task itself is not’ (Logan, 1978, p. 57). In stop tasks with only one signal, stopping could be a prepared reflex due to the low signal selection demands. Once the task instructions are implemented (`IF signal THEN stop’), the stop process can be triggered easily by the presentation of the stop signal; consequently, stop processing and rule-based (or algorithmic) primary-task processing can occur in parallel without much dual-task interference (cf. Kahneman, 2003; Logan, 1979, 1988; Schneider Shiffrin, 1977; Shiffrin Schneider, 1977). We should point that capacity sharing can occur in stop-signal tasks with a single stop signal. The stop rate parameters depend on the discriminability, intensity, and modality of the stop signal (e.g. van der Schoot, Licht, Horsley, Sergeant, 2005), which could be interpreted as a capacity limitation (Logan et al., 2014). Furthermore, we have recently demonstrated that competition between visual signals in the go and the stop tasks influences stopping (Verbruggen, Stevens, Chambers, 2014), which is consistent with the idea that stimuli have to compete for limited processing capacity. Thus, it seems that under certain circumstances, capacity sharing may also occur in simple stop-signal tasks. 3.4. Categorically different stopping strategies? Maybe not Our results are very similar to those observed in previous selective stop studies. As discussed above, two main selective stopping strategies have been proposed in this literature: the `Stop then Discriminate’ strategy (also know as the `Stop-Restart’ strategy; e.g. Aron, Behrens, Smith, Frank, Poldrack, 2007) and the `Discriminate then Stop’ strategy. To distinguish between these two strategies, researchers have relied on differences between nosignal RTs, signal espond RTs, and invalid-signal RTs. But our analysis indicates that such RT differences could be due to capacity sharing and the difficulty of the discrimination process. In other words, our study indicates that RT differences between the groups, subjects, or conditions in selective stop tasks could be quantitative (i.e. degree of capacity sharing) rather than qualitative (i.e. different strategies). This is not to say that strategies have no role in selective stop tasks. Many studies indicate that people use various strategies.