Simultaneity and Temporal Order Judgments Exhibit Distinct Reaction Times and Training Effects.

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Psychophysics

Background:

• Sensory research extensively studies simultaneity judgments (SJ) and temporal order judgments (TOJ).
• A key question is whether neural events at early sensory stages or later, task-specific stages limit SJ and TOJ performance.
• Distinguishing these possibilities is crucial for understanding temporal perception mechanisms.

Purpose of the Study:

• To investigate whether the limits on simultaneity judgments (SJ) and temporal order judgments (TOJ) arise from early sensory processing or distinct, task-specific neural events.
• To differentiate the underlying neural mechanisms governing SJ and TOJ using a novel reaction-time (RT) measure and perceptual learning.

Main Methods:

• Developed a novel reaction-time (RT) measure within a perceptual learning paradigm.
• Utilized dual-stream Rapid Serial Visual Presentation (RSVP) displays with red-letter and black-number targets.
• Participants performed either SJ or TOJ tasks on stimuli presented in opposite visual hemifields.

Main Results:

• Simultaneity judgments (SJ) showed faster RTs for synchronized targets, while temporal order judgments (TOJ) showed faster RTs for asynchronized targets.
• These distinct RT patterns indicate task-specific decision spaces, not early sensory processing limits.
• Perceptual learning for SJ did not transfer to TOJ, and vice versa, further supporting distinct task mechanisms.

Conclusions:

• The findings provide novel evidence that distinct neural rules and task-specific decision spaces, rather than early stimulus-driven sensory stages, govern the limits of simultaneity and temporal order judgments.
• This challenges the notion of a unified early sensory limit for temporal perception tasks.
• The lack of training transfer underscores the specialized nature of the neural mechanisms underlying SJ and TOJ.