Using Variables

Experiments Surveys & forms

Variables let you embed dynamic content anywhere in your trial file (feedback text, instructions, stimulus text, or form questions) by using the %variable% placeholder syntax.

Syntax

Wrap any variable name in percent signs:

feedback = You responded in %RT% ms.

At runtime Testable replaces %variable% with the actual value.

Built-in response variables

These are populated automatically from the current trial’s outcome:

Variable	Value
%response%	Participant’s response (text or button label)
%RT%	Reaction time in milliseconds
%correct%	1 if correct, 0 if not

Note

For button responses %response% stores the response position index (1-based), not the button label. For text input responses it stores the literal text.

Caution

In type = form trials, you cannot use %response% to reference a question on the same page. The referencing trial must be separated by a pageBreak. Place a pageBreak row between the question you want to reference and the row that uses its %response% value.

Historical trial variables

Reference outcomes from earlier trials:

Variable	Retrieves
%response3%	Response from trial file row 3
%response-1%	Response from the previous trial
%response[trialA]%	Response from the trial with label = trialA
%correct[trialA]%	Correct/incorrect from labelled trial
%RT3%	RT from trial file row 3

Aggregate statistics

Compute a summary statistic over a range of past trials:

Syntax: %variable.function[range]%

Functions

Function	Result
mean	Arithmetic mean (avg is a synonym)
modal	Mode
sum	Sum
min	Minimum
max	Maximum
count	Count of 1 values (e.g. number correct)
perc	Percentage of 1 values (useful for accuracy)

Range formats

Format	Meaning
[2,3,4]	Specific trial rows
[-4_0]	Last 5 trials (relative; 0 = current)
[-9_-5]	Trials from 10 back to 6 back

Examples:

feedback = Mean RT over last 10 trials: %RT.mean[-9_0]% ms
feedback = Accuracy: %correct.perc[-49_0]%%
feedback = You got %correct.count[1,2,3,4,5]% of 5 correct.

Participant details variables

These are automatically populated from the participant details form (if enabled):

Variable	Value
%id%	Participant ID
%gender%	Gender
%age%	Age
%education%	Education level
%handedness%	Handedness
%nationality%	Nationality
%customvar1%	First custom variable

URL parameter variables

Parameters passed in the experiment URL are automatically available as variables and are forwarded to outgoing redirect URLs. For example, if the experiment URL includes ?participant=P001, you can use %participant% in your content.

Path variables

You can also embed variables directly in URL path segments, not just query parameters. For example:

https://example.com/%age%/%nationality%/?id=%id%

If a 29-year-old participant from Chile with ID M1234 completes the study, the redirect URL becomes:

https://example.com/29/Chile/?id=M1234

This is useful when your external platform expects specific values in the URL path rather than as query parameters.

Defining your own variables

To define your own variables or build lists during the experiment, see Scripts.

Next steps

• Feedback: use variables in feedback text
• Generating Questions from Lists: use lists with variable syntax
• How to Inject Logic: use response values in conditions