Reexamining the effects of speed-accuracy instructions with a diffusion-model-based analysis.

Area of Science:

• Cognitive psychology
• Computational neuroscience

Background:

• Understanding how cognitive processes adapt to task demands (speed vs. accuracy) is crucial.
• Previous research often assumed fixed parameters during speed-accuracy trade-off (SAT) manipulations.

Purpose of the Study:

• To investigate which parameters of the diffusion model change under speed and accuracy stress.
• To examine the role of across-trial variability in drift rate.

Main Methods:

• Applied the standard diffusion model to over one million responses from four large-scale experiments.
• Allowed all model parameters to vary freely between speed and accuracy conditions.
• Conducted a secondary analysis fixing across-trial drift rate variance.

Main Results:

• Boundary separation and non-decision time were the most affected parameters under speed stress.
• Drift rates showed minimal direct effects, but their across-trial variability changed, canceling out impacts on accuracy and response time.
• High-stress conditions also reduced drift rates, potentially due to restricted encoding.

Conclusions:

• Decision-making parameters, particularly boundary separation and non-decision time, are modulated by speed-accuracy instructions.
• Across-trial variability in drift rate plays a key role in maintaining accuracy and response time consistency.
• Severe speed stress may impair perceptual encoding, impacting multiple decision-making parameters.