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Locus of the intensity effect in simple reaction time tasks
Piotr Jaśkowski1, Marta Kurczewska, Agnieszka Nowik
1Department of Cognitive Psychology, University of Finance and Management, Warsaw, Poland. jaskowski@vizja.pl
Perception & Psychophysics
|December 15, 2007
Summary
Stimulus intensity affects reaction time by influencing early sensory processing, not motor responses. This study clarifies the timing of stimulus intensity effects on information processing in reaction tasks.
Area of Science:
- Cognitive psychology
- Neuroscience
- Human factors
Background:
- The precise location of the stimulus intensity effect within the reaction time (RT) process remains debated.
- Previous research yielded mixed results, particularly for auditory stimuli, possibly due to limited intensity ranges and task complexity.
Purpose of the Study:
- To investigate the locus of the stimulus intensity effect on information processing during reaction tasks.
- To clarify whether stimulus intensity impacts sensory or motor components of RT.
Main Methods:
- Three experiments were conducted using broader ranges of stimulus intensities and simple reaction tasks.
- Stimulus-locked (S-LRP) and response-locked (R-LRP) lateralized readiness potentials were measured as indicators of sensory and motor processes, respectively.
Main Results:
- Stimulus intensity significantly affected S-LRP onset, mirroring changes in RT across both visual and auditory modalities.
- The effect of stimulus intensity on R-LRP was minimal, suggesting motor processes were not directly modulated.
- S-LRP changes correlated with RT reductions, indicating an earlier processing locus.
Conclusions:
- Stimulus intensity primarily influences the sensory stages of information processing, preceding motor execution.
- The findings support the role of S-LRP and R-LRP in differentiating sensory and motor contributions to reaction time.
