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Do the dynamics of prior information depend on task context? An analysis of optimal performance and an empirical test.

van Ravenzwaaij D, Mulder MJ, Tuerlinckx F, Wagenmakers EJ - Front Psychol (2012)

Bottom Line: In this model, prior information or advance knowledge about the correct response can manifest itself as a shift in starting point or as a shift in drift rate criterion.These two mechanisms lead to qualitatively different choice behavior.Firstly, we demonstrate that optimal behavior for biased decision problems is prescribed by a shift in starting point, irrespective of variability in stimulus difficulty.

View Article: PubMed Central - PubMed

Affiliation: Psychological Methods, University of Amsterdam Amsterdam, Netherlands.

ABSTRACT
In speeded two-choice tasks, optimal performance is prescribed by the drift diffusion model. In this model, prior information or advance knowledge about the correct response can manifest itself as a shift in starting point or as a shift in drift rate criterion. These two mechanisms lead to qualitatively different choice behavior. Analyses of optimal performance (i.e., Bogacz et al., 2006; Hanks et al., 2011) have suggested that bias should manifest itself in starting point when difficulty is fixed over trials, whereas bias should (additionally) manifest itself in drift rate criterion when difficulty is variable over trials. In this article, we challenge the claim that a shift in drift criterion is necessary to perform optimally in a biased decision environment with variable stimulus difficulty. This paper consists of two parts. Firstly, we demonstrate that optimal behavior for biased decision problems is prescribed by a shift in starting point, irrespective of variability in stimulus difficulty. Secondly, we present empirical data which show that decision makers do not adopt different strategies when dealing with bias in conditions of fixed or variable across-trial stimulus difficulty. We also perform a test of specific influence for drift rate variability.

No MeSH data available.


Related in: MedlinePlus

Fixed difficulty (η = 0) in the free response paradigm. Minimum MRT is achieved when all bias is accounted for by a shift in starting point z. Bias β = 0.8, boundary separation a = 0.12. Top panel: Parameter combinations of starting point as a ratio of boundary separation z/a and shift in drift rate criterion vc that lead to the same fixed level of accuracy (90% for v = 0.2, 95% for v = 0.3). Bottom panel: Mean RT that corresponds to the parameter combinations of the top panel.
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Figure 6: Fixed difficulty (η = 0) in the free response paradigm. Minimum MRT is achieved when all bias is accounted for by a shift in starting point z. Bias β = 0.8, boundary separation a = 0.12. Top panel: Parameter combinations of starting point as a ratio of boundary separation z/a and shift in drift rate criterion vc that lead to the same fixed level of accuracy (90% for v = 0.2, 95% for v = 0.3). Bottom panel: Mean RT that corresponds to the parameter combinations of the top panel.

Mentions: Firstly we considered the following set of parameters: mean drift rate v = 0.2, boundary separation a = 0.12, and bias β = 0.85. The top-left panel of Figure 6 shows that an accuracy level of 90% may be achieved by a combination of shifts for starting point z and shifts of drift rate criterion vc. Again, both parameters exist in a trade-off relationship, such that higher values of z combined with lower values of vc produce the same mean proportion correct.


Do the dynamics of prior information depend on task context? An analysis of optimal performance and an empirical test.

van Ravenzwaaij D, Mulder MJ, Tuerlinckx F, Wagenmakers EJ - Front Psychol (2012)

Fixed difficulty (η = 0) in the free response paradigm. Minimum MRT is achieved when all bias is accounted for by a shift in starting point z. Bias β = 0.8, boundary separation a = 0.12. Top panel: Parameter combinations of starting point as a ratio of boundary separation z/a and shift in drift rate criterion vc that lead to the same fixed level of accuracy (90% for v = 0.2, 95% for v = 0.3). Bottom panel: Mean RT that corresponds to the parameter combinations of the top panel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351677&req=5

Figure 6: Fixed difficulty (η = 0) in the free response paradigm. Minimum MRT is achieved when all bias is accounted for by a shift in starting point z. Bias β = 0.8, boundary separation a = 0.12. Top panel: Parameter combinations of starting point as a ratio of boundary separation z/a and shift in drift rate criterion vc that lead to the same fixed level of accuracy (90% for v = 0.2, 95% for v = 0.3). Bottom panel: Mean RT that corresponds to the parameter combinations of the top panel.
Mentions: Firstly we considered the following set of parameters: mean drift rate v = 0.2, boundary separation a = 0.12, and bias β = 0.85. The top-left panel of Figure 6 shows that an accuracy level of 90% may be achieved by a combination of shifts for starting point z and shifts of drift rate criterion vc. Again, both parameters exist in a trade-off relationship, such that higher values of z combined with lower values of vc produce the same mean proportion correct.

Bottom Line: In this model, prior information or advance knowledge about the correct response can manifest itself as a shift in starting point or as a shift in drift rate criterion.These two mechanisms lead to qualitatively different choice behavior.Firstly, we demonstrate that optimal behavior for biased decision problems is prescribed by a shift in starting point, irrespective of variability in stimulus difficulty.

View Article: PubMed Central - PubMed

Affiliation: Psychological Methods, University of Amsterdam Amsterdam, Netherlands.

ABSTRACT
In speeded two-choice tasks, optimal performance is prescribed by the drift diffusion model. In this model, prior information or advance knowledge about the correct response can manifest itself as a shift in starting point or as a shift in drift rate criterion. These two mechanisms lead to qualitatively different choice behavior. Analyses of optimal performance (i.e., Bogacz et al., 2006; Hanks et al., 2011) have suggested that bias should manifest itself in starting point when difficulty is fixed over trials, whereas bias should (additionally) manifest itself in drift rate criterion when difficulty is variable over trials. In this article, we challenge the claim that a shift in drift criterion is necessary to perform optimally in a biased decision environment with variable stimulus difficulty. This paper consists of two parts. Firstly, we demonstrate that optimal behavior for biased decision problems is prescribed by a shift in starting point, irrespective of variability in stimulus difficulty. Secondly, we present empirical data which show that decision makers do not adopt different strategies when dealing with bias in conditions of fixed or variable across-trial stimulus difficulty. We also perform a test of specific influence for drift rate variability.

No MeSH data available.


Related in: MedlinePlus