undodraw attribute

The undodraw attribute specifies conditions in which any drawing on a given trial should be erased.

Member of

<trial>

Syntax

/ undodraw = [expression; expression; expression; ...]

Parameters

expression

One or more expressions, delimited by semi-colons. See help with expression syntax for more information.

Remarks

This parameter evaluates one or more specified expressions at the end of a trial. If the expressions evaluate to true, any drawing on that trial will be removed from the screen. This attribute thus provides a mechanism for a give task to allow participants to undo drawing mistakes (e.g., tracing to the incorrect target in the Trail Making Test.

Examples

The following trial erases a drawing if the participant clicks on an "undo" button placed on the screen.

<trial mytrial>
/ stimulusframes = [1=start, undo]
/ undodraw = [trial.mytrial.response == "undo"]
</trial>