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Stop Signal Task output

sibylle.petersen — Sun, 31 May 2015 14:44:27 GMT

Dear all

I plan to use the Stop Signal Task in one of my studies. I have looked at the script in the task library and the paper by Verbruggen et al., 2008.

I am very unsure how to interpret the output. If anyone could briefly respond whether my ideas about how to interpret these values are correct (see below) I would be very grateful.

Thank you and have a good day

Sibylle

expressionsp_rs:p respond if signal?
expressionsssd: delay stop signal?
expressionsssrt :covert latency of the stop process?
expressionssr_rt: mean signal respond reaction time?
expressionsns_rt: reaction times no-signal trials?
expressionsns_hit: percentage hits no-signal trials?
expressionsmiss: percentage misses in no-signal trials?
expressionsz_score:probability to inhibit
expressionsp_value: probability to inhibit

RE: Stop Signal Task output

Dave — Sun, 31 May 2015 14:44:27 GMT

Sure. If you look at Verbruggen et al. (2008), p. 482, you'll find:

The following variables are estimated or calculated:

- mean p(respond|signal),
- mean SSD,
- SSRT,
- mean signal-respond RT,
- no-signal RT,
- percentage of correct responses on no-signal trials, and the
- percentage of missed responses on no-signal trials.

[...] will also calculate a

- z score and the corresponding
- p value

to indicate whether each subject inhibited significantly more or less than 50% of the time.

These correspond to

- expressions.p_rs
- expressions.ssd
- expressions.ssrt
- expressions.sr_rt
- expressions.ns_rt
- expressions.ns_hit
- expressions.miss
- expressions.z_score
- expressions.p_value

in the order given. The variable names follow those in the original program by Verbruggen et al.