A variable valued attribute can change its value from trial to trial according to a specified selection algorythm.

Applies to

<defaults> <block> <trial> <namingtrial> <openended> <likert> <response> <instruct> <text> <picture> <video> <shape> <sound>

Syntax

or

or

or

or

or

Parameters

integer	An integer value.
selectionmode	One of the following values: Value Description noreplace Randomly selects without replacement. noreplacecorrect Randomly selects without replacement unless an incorrect response is given. noreplaceerror Randomly selects without replacement unless a correct response is given. replace Randomly selects with replacement. constant Selects a single constant value.
dependency	One of the following values: Value Description noreplacenot Randomly selects without replacement, reselecting the item if it matches the currently selected item of the specified stimulus or counter. replacenot Randomly selects with replacement, reselecting the item if it matches the currently selected item of the specified stimulus or counter. linked Selects the current item of the specified stimulus or counter.
stimulusname	The name of a stimulus defined elsewhere in the script.
countername	The name of a counter defined elsewhere in the script.
pool	A set of numbers representing the selection pool.

Remarks

Attributes with variable values can be assigned a randomly selected or predefined sequence of values. The attribute assumes progresses through the sequence with every new block or trial.

Examples

The following text stimulus is displayed, from trial to trial, in a sequence of four positions along the upper-left to lower-right diagnal of the screen:

<text vicepresidents>
/ items = vicepresidentitems
/ select = linked(presidents)
/ hposition = sequence(0, 25, 75, 100)
/ vposition = sequence(0, 25, 75, 100)
</text>

The following trial pauses for a randomly selected duration ranging from 50 to 1000 milliseconds:

<trial unpredictable>
/ pretrialpause = replace(50 - 1000)
/ stimulusframes = [1 = target)
</trial>

The following block timeouts after 5 seconds on the first run, 4 seconds on the second run, and 3 seconds on the third:

<block moutains>
/ trials = (1-10=reactiontest)
/ timeout = sequence(5000, 4000, 3000)
</block>