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The embedded set procedure. Comment on Galbraith, MacCrimmon, and Steffy
1Department of Psychiatry, University of Maryland School of Medicine, Baltimore 21228.
The Journal of Nervous and Mental Disease
|December 1, 1988
Summary
The reaction-time crossover phenomenon is primarily influenced by slow reaction times in initial trials within short preparatory intervals. Uncontrolled preparatory interval durations also affect crossover, suggesting a need to revisit original methodologies.
Area of Science:
- Cognitive Psychology
- Neuroscience
- Psychophysiology
Background:
- The reaction-time crossover phenomenon, initially described by Rodnick and Shakow, is typically studied using the embedded isotemporal sets procedure.
- This phenomenon is indexed by reaction time differences between regular and irregular trials at a 7-second preparatory interval (PI).
- Previous research indicated that the magnitude of crossover at a 7-second PI is influenced by the duration of the preparatory interval immediately prior (PPI).
Purpose of the Study:
- To further investigate the influence of preparatory interval (PI) duration on the reaction-time crossover phenomenon.
- To analyze secondary data to understand the specific contributions of PPI durations to crossover effects within the embedded sets procedure.
- To provide additional evidence supporting the recommendation to return to the original Rodnick-Shakow methodology.
Main Methods:
- Secondary analysis of data from studies employing the embedded isotemporal sets procedure.
- Examination of reaction times to regular and irregular trials across varying preparatory interval (PI) durations (1, 3, and 7 seconds).
- Assessment of the influence of preparatory interval immediately prior (PPI) on reaction time crossover magnitude.
Main Results:
- The crossover phenomenon, as measured by the embedded sets procedure, is significantly affected by slow reaction times to the first trial in 1-second isotemporal blocks.
- Uncontrolled PPI durations across 1-, 3-, and 7-second embedded blocks partially contribute to the observed crossover effects.
- Reaction time variability is notably higher at the beginning of shorter PI blocks.
Conclusions:
- The embedded isotemporal sets procedure may not accurately capture the true reaction-time crossover phenomenon due to slow initial trial responses and PPI variability.
- The findings reinforce the need to reconsider the methodologies used for studying reaction-time crossover.
- Returning to the original Rodnick-Shakow method is recommended for more robust and reliable investigation of this phenomenon.