SPRT is optimal in the sense that it minimizes expected decision time for any given accuracy level, and maximizes accuracy for a given decision time ( Wald & Wolfowitz, 1948). Bogacz et al. (2006) have argued that optimality may be a hallmark of human cognitive control, the ability to adapt information processing from moment to moment depending on current goals. According to this view, the DDM may provide a privileged framework to study such control processes, and offers an interesting departure point to approach decision-making in conflicting situations. Two properties are predicted by the DDM when task difficulty (drift selleck kinase inhibitor rate) is manipulated. Those

properties have so consistently been observed in both detection1 and choice experiments that psychologists have proposed them to be psychological laws. First, the Selleck NVP-BKM120 mean and standard deviation (SD) of RT distributions increase at approximately the same rate when drift rate declines. Empirically, the linear relationship between the mean and SD of RT distributions holds for a broad range of paradigms and generally leads to very high correlations for each individual (Pearson’s r > .85; Luce, 1986 and Wagenmakers and Brown, 2007; hereafter referred to as Wagenmakers–Brown’s law). Second, the chronometric function

predicted by the DDM when the two alternatives are equiprobable is an hyperbolic tangent function of these the following form: MeanRT=aμtanhaμσ2+Terwhere a, μ, and σ2 are respectively the boundary, drift rate, and diffusion coefficient of the diffusion process ( Ratcliff, 1978). Ter is the non-decision time. For a suprathreshold range of stimulus intensities, this function mimics Piéron’s law (see Palmer, Huk, & Shadlen, 2005, Experiment 3). Piéron’s law states that mean RT decreases as a power function of the intensity of a stimulus according to: MeanRT=αI-β+γwhere α is a scaling

parameter, I represents stimulus intensity, γ the asymptotic RT, and β determines the rate of decay of the curve ( Piéron, 1913). Although initially investigated in the context of detection tasks (e.g., Chocholle, 1940), Piéron’s law has proven to hold in choice experiments ( Palmer et al., 2005, Pins and Bonnet, 1996, Stafford et al., 2011 and van Maanen et al., 2012). In conclusion, Piéron and Wagenmakers–Brown’s laws are consistent with the diffusion framework, and may reflect a general tendency of human decision-makers to approach optimal behavior. Besides “simple” situations, one often has to make decisions in a multiple stimuli environment, only some of those stimuli being relevant for the task at hand. One source of paradigms designed to study such situations are so-called conflict tasks. Empirical findings in these tasks converge toward an apparent stimulus–response (S–R) compatibility effect.