AbstractDefining reaction time (RT) as the time from stimulus presentation to movement initiation is well-established. However, when using a go-before-you-know paradigm, participants respond to one of four potential targets before completing response selection and programming. Previously we tested if the presence of an auditory cue at movement onset would speed up performance in the go-before-you-know paradigm. Movement initiation was defined using a velocity threshold (30mm/s for 30msec). The target location and auditory cue were presented immediately following movement initiation. Therefore, the finding that the valid auditory cues led to shorter RTs was unexpected. Given the task characteristics, early stages of movement execution might have been captured within RT. Thus, the present research aimed to examine how to best define movement initiation with the go-before-you-know task where movement planning is completed during early movement execution. We re-analyzed the data using a new movement initiation velocity threshold of >15mm/s. We also analyzed the RT data recorded from the micro-switch. Although the re-analysis led to a significant loss of data due to the exclusion of faster movements, the results indicated no statistically significant effect of auditory condition on reaction time [F (2,18) =0.23, p= 0.80]. These results were consistent with the micro-switch data analysis [F (2,18) =0.09, p=0.91]. Consistent with Blinch and DeWinne (2019), mean RTs using a velocity threshold (251ms) were shorter than those recorded by the micro-switch (297ms). The go-before-you-know-paradigm facilitates examining response programming and selection in real-time, resulting in a need to critically examine how best to define movement initiation.
Acknowledgments: The Funding for this project was provided by Natural Sciences and engineering research council of Canada.