Clocking perceptual processing speed: From chance to 75% correct in less than 30 milliseconds

Area of Science:

• Neuroscience
• Cognitive Science
• Decision Making

Background:

• Studying the neural basis of choice behavior is crucial.
• Traditional methods struggle to separate perceptual judgment from motor response timing.
• Reaction times (RTs) are influenced by confounding sensory and motor factors.

Purpose of the Study:

• To develop a novel task to precisely measure the timing of perceptual judgments.
• To overcome limitations of previous reaction time (RT) studies.
• To investigate the temporal dynamics of choice commitment and underlying neural mechanisms.

Main Methods:

• Designed a new task to isolate perceptual judgment from motor execution.
• Introduced a "tachometric" curve to analyze the unfolding of perceptual judgment over time.
• Measured psychophysical and neuronal responses in monkeys performing a color discrimination task.

Main Results:

• The "tachometric" curve's slope reflects perceptual difficulty and capacity, independent of motor execution.
• Monkeys achieved accurate color discrimination in less than 30 milliseconds.
• Established a novel metric for correlating psychophysical and neuronal response time courses.

Conclusions:

• The new method accurately quantifies perceptual judgment timing.
• Choice commitment can occur very rapidly, within tens of milliseconds.
• This approach opens new avenues for studying choice behavior and neural correlates across diverse conditions.