Brain Imaging & Analysis Center

usage: rwait id flg start duration

The RWAIT command in a ShowPlay stimulus list causes the stimulus presentation to pause until the subject has made a response. The response can be either a keyboard/mouse response, or a button box response.

The start time of the RWAIT command specifies when the pause should occur (relative to the most recent RESET command).

The duration of the RWAIT command can be used to specify a time-out interval. If the duration is 0, the pause will extend indefinitely until a response is made. If the duration is greater than 0, it specifies a time-out interval (in milliseconds). The pause will automatically end after the time-out interval even if there was no response. The response code returned after a RWAIT timeout is whatever value is specified in the “timout_resp” variable (default code is 127). Change that value if you want a different default (time-out) response. The sampling resolution for the response timout is specified by the “toutintrvl” variable (in milliseconds). By default TOUTINTRVL is 100, which means that the time-out pause will end within 100 ms of the specified time. Shorten the sampling rate if you need more accurate time-out control, but use the default value for greater efficiency if you don't need the extra resolution.

Note: It is usually a good idea to have a RESET command follow immediately after a RWAIT command, with the same start time for both the RWAIT and the RESET. That way, as soon as the pause terminates the clock is reset. Subsequent stimulus start times in the list will therefore be relative to the end of the RWAIT pause, facilitating flexible self-paced tasks.

For example,

"Press a button" 1 1 1000 0 -1 -1
rwait 0 0 1000 2000
reset 0 0 1000
"Press button 2" 2 1 0 0 -1 -1

This will tell the subject to press a button, then wait up to 2 seconds for a response. As soon as the subject responds (or after the 2 seconds), the subject will be instructed to press button 2.

See Also:
Paradigm parameter file, Stimulus table

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