Response biases in simple decision making: Faster decision making, faster response execution, or both?

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Factors

Background:

• Response bias in decision tasks leads to faster preferred responses.
• Sequential sampling models explain RT differences via evidence accumulation.
• Non-decision processes, like motor execution, may also contribute to response time biases.

Purpose of the Study:

• To investigate the roles of decision and non-decision processes in response time (RT) bias.
• To determine how response execution speed affects biased decision-making.
• To differentiate contributions of perceptual decision-making versus motor response factors to RT.

Main Methods:

• Two experiments were conducted involving directional choices (arrow stimuli) and a visual discrimination task (asterisk counts).
• Participants responded using joystick movements or keypresses, with varying stimulus probabilities and response requirements.
• Response times (RT) and accuracy were measured under predictable and unpredictable conditions.

Main Results:

• Motor execution times were significantly faster for expected stimulus directions compared to unexpected ones.
• Decision times were quicker for more probable stimulus classes.
• The bias effect on RT was amplified when both stimulus class and motor response were predictable.

Conclusions:

• Both decision processes (evidence accumulation) and non-decision processes (motor execution) contribute to response time biases.
• Anticipation of both stimulus and response enhances the bias effect on RT.
• Understanding these dual factors is crucial for explaining reaction time differences in biased choices.