Feedback

Experiments

Testable can display feedback to participants after each trial. Feedback text is defined in the **`feedback`** column and can include dynamic variables that show the actual response, reaction time, or accuracy.

Two dependencies to know up front:

• Feedback runs only on test and practice trials. It never fires on learn, instructions, or form rows.
• Feedback based on accuracy (correct: / incorrect: messages) requires the key column: correct and incorrect are the result of scoring the response against key, so without it those messages never match.

Feedback in surveys

There is no out-of-the-box feedback for form rows. To react to a survey answer, use the if / then logic columns to route the participant to a follow-up screen; see How to Inject Logic.

Unconditional feedback

Set the feedback column to the text you want participants to see after every response:

feedback = Thanks! On to the next one.

Feedback by outcome

Write key: message segments, separated by semicolons, to show a different message depending on how the trial ended:

Key	When it appears
timeout: ...	No response was given before the responseWindow deadline. Only meaningful when the trial has a deadline.
[response]: ...	Participant gave that specific response (as it appears in results: a key token like a, a button number like 1)
correct: ...	Response scored correct against key
incorrect: ...	Response scored incorrect against key
bare text (no colon)	Catch-all, shown when nothing above matched

feedback = correct: Well done!; incorrect: Try again.; timeout: Please respond faster.

Segments are checked in the order of the table above (timeout first, then the specific response, then correctness, then the catch-all); the first match is shown, and if nothing matches the feedback screen is skipped entirely.

Caution

A trial that times out shows no feedback at all unless a timeout: segment is defined; the incorrect: and catch-all messages do not cover timeouts. Whenever a trial has a deadline, add a timeout: segment.

Per-response messages

Using the response itself as the key works with response labels too. For buttons Cat and Dog:

feedback = Cat: You chose the cat.; Dog: You chose the dog.

Feedback variables

Use %variable% placeholders in your feedback text. These are replaced with the participant’s actual values when the trial runs.

Variable	Value
%response%	The participant’s response
%RT%	Reaction time in ms
%correct%	1 if correct, 0 if incorrect

Examples:

feedback = Your reaction time was %RT% ms.
feedback = correct: Correct! You pressed %response% in %RT% ms.; incorrect: Incorrect.

Historical trial variables

You can reference responses 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 labelled trialA

Computed aggregate feedback

Display summary statistics computed over a range of trials:

Syntax: %variable.function[range]%

• variable: RT or correct
• function: mean (or avg), modal, sum, min, max, perc (percentage correct), count (number correct)
• range: a list [2,3,4] or a range [-5_0] (last 5 trials up to and including current)

Examples:

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

Note

perc gives the percentage as a number (e.g. 75), not a fraction. Append % after the closing % to display a percentage sign.

How feedback is displayed

feedbackTime: how long, and how the screen ends

A number is a duration in ms; the feedback shows for that long, then the trial ends automatically:

feedbackTime = 1500

With feedbackTime left empty, the feedback does not auto-advance: a NEXT button is shown, and the participant clicks it to continue.

feedbackOptions: where it appears

Value	Effect
(empty)	Feedback appears after the stimuli are cleared
center	Feedback is centred on screen
sameScreen	The stimuli and buttons stay visible under the feedback instead of being cleared

These two flags are the only options; anything else in the cell is silently ignored. To colour the feedback text, use the color column (see Other Visual Content).

Adding images to feedback

You can display images in the feedback column using HTML. First upload the image to your project’s Stimuli tab, then reference it:

feedback = <img src="stimuli/yourImageName.png">

For condition-specific image feedback:

feedback = correct: <img src="stimuli/correct.png">; incorrect: <img src="stimuli/incorrect.png">

Next steps

• Timing Parameters: control when feedback appears relative to trial timing
• Using Variables: full reference for all variable types