Figure 2.

(A) Information processing during a Simon task as modelled by the Activation-Suppression model [e.g., Ridderinkhof (2002)]. The relevant stimulus dimension (color in the Simon task) is processed via the slow, indirect, processing route. Simultaneously, irrelevant stimulus location is processed via the fast, direct, processing route. Activation of the location-based response activation is inhibited by selective suppression (shown here in red), which facilitates execution of the correct, color-based, action. The selective suppression takes time to develop, which results in a relatively high proportion of fast erroneous (location-based) responses on incongruent trials, with near-perfect response accuracy when responses are slower as the inappropriate responses have been suppressed. These effects seen by plotting response accuracy as a function of response time in a Conditional Accuracy Function (CAF) as shown in (B). Furthermore, the interference on incongruent trials would be expected to reduce as unwanted responses are suppressed as RTs increase. This effect can be seen in the negative slope of a delta plot, as shown in (C). Delta plots can reveal individual and group differences in motor activation and suppression that cannot be seen in average measures of RT. Panels (B) and (C) were originally published in van den Wildenberg et al. (2010). Front. Hum. Neurosci. 4:222. doi: 10.3389/fnhum.2010.00222. Panel (B) was modified after Wylie et al. (2009), with permission from Elsevier. Panel (C) was modified after Wylie et al. (2010).