The numframes attribute specifies the total number of vertical retrace frames making up the stimulus presentation sequence for a trial.
<likert> <openended> <slidertrial> <trial>
integer | A non-negative integer specifying the number of frames. |
In most cases, the numframes attribute need not be specified, in which case the number of frames is equal to last frame specified by the stimulusframes attribute. The numframes attribute is useful for extending the stimulus frames sequence beyond the frame at which the last stimuli are presented. For example, a task that displays a single stimulus on the screen for a certain number of retrace frames before allowing the subject to respond could use the numframes command to do so.
See How to Control Trial Duration and Inter-Trial Intervals for related information.
The following trial presents a single text stimulus on the screen for 20 frames before allowing the subject to respond.
<trial mytrial>
/ stimulusframes=[1=sometext]
/ numframes=20
</trial>