Previous investigation on examining concurrence costs in secondary tasks following quick reactions indirectly found that speed-accuracy trade-off strategies by participants influenced results (Hendrick, 2008). The purpose of this study was to more systematically identify the strategies used by participants in order to examine its effect on RT performance followed by speeded and non-speeded secondary tasks.
Method
Participants (N=26) were tested on two days with 30 trials per condition each day with the order of conditions randomly varied. In response to a visual stimulus, they were asked to move their hand to a particular button as quickly as possible. In the secondary task conditions, participants then picked up a small object and pressed a second response button as quickly as possible (speeded) or at their leisure (non-speeded). After testing on day 2, participants were given a short questionnaire regarding the strategies they employed. RTs under the four conditions were compared: Control (simple RT), 2-choice go/no-go, and 2-choice go/no-go followed by a non-speeded secondary task and followed by a speeded secondary task.
Analysis/Results
There was a significant condition effect (p < .05) with simple RT the fastest condition overall (M=275 ms, SE=7.9 ms) and the non-speeded secondary task the slowest (M=423 ms, SE=16.0 ms). There was no significant difference between the go/no-go and the speeded secondary task conditions (M=377 ms, SE=9.8 ms and M=365 ms, SE=10.0 ms, respectively). When comparing RT based on the self-disclosed strategies in the speeded condition, there were no significant differences (p > .05). In the non-speeded secondary task condition however, RT did differ significantly based on the strategy used (p < .05). Participants who indicated that they focused on reacting quickly to the stimulus were significantly faster than those who indicated they focused more on leisurely picking up the object rather than on reacting (M=354 ms, SE=20.3 ms and M=449 ms, SE=16.0 ms, respectively). When reanalyzing the data for the eight participants who in fact followed the instructions (to react as quickly as possible), simple RT was still the fastest (M=256 ms, SE=4.9 ms), however there was no significant differences among the other three 2-choice conditions.
Conclusions
When controlling for strategies used by the participants, results support earlier findings that performing a secondary task (in this case speeded or non-speeded) did not delay the initial response. Since results did in fact vary across subjects, researchers can not assume that participants are always following the given instructions.
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