How to Inject Logic

Experiments Surveys & forms

Testable lets you add conditional branching to any trial sequence using the **`if`** and **`then`** columns. When the condition in `if` is met Testable executes the instruction in `then`; otherwise it moves to the next row.

Basic structure

Column	Value
if	A condition to evaluate
then	What to do when the condition is true

Both columns must be on the same row. If either is blank on a row, logic is not applied to that trial.

Conditions (if)

Condition	Matches when
correct	Participant responded correctly
incorrect	Participant responded incorrectly
RT > 500	Reaction time was greater than 500 ms
RT < 300	Reaction time was less than 300 ms
response = cat	Participant’s response text equals cat
responseCode = 2	Participant selected the second option

Negation

Prefix a condition with ! to invert it:

if = !correct

Combining conditions

Use & to require multiple conditions simultaneously:

if = correct & RT < 500

Partial string match

Use has() to check whether the response contains a substring:

if = response has(cat)

Multiple pairs

Separate multiple condition–action pairs with ; on the same row to evaluate them in sequence:

if = correct; RT < 300
then = end; +1

The first condition is paired with the first then value, the second with the second, etc.

Destinations (then)

Destination	Goes to
30	Trial file row 30
trialA	The trial labelled trialA in the label column
+2	Two rows forward from the current row
-1	One row back
end	Skip to the end of the experiment
screenout	Remove participant from the study (screener mismatch)
https://example.com	Redirect participant to an external URL

Caution

screenout is only triggered within the first 5 trials. Use it together with screener survey questions at the start of the experiment.

Labelling target rows

Use the label column (an organisation column) to give a row a name, then reference it in then:

label = startBlock2
...
then = startBlock2

This is more maintainable than hard-coding row numbers, which change when you add or remove rows.

Example: practice loop

label = practiceStart
...
if    = incorrect
then  = practiceStart

If the participant responds incorrectly they are looped back to the start of the practice block.

Example: adaptive study

if    = correct & RT < 400
then  = +3

If the participant was both correct and fast, skip 3 rows to a harder condition.

Next steps

• Screener Surveys: use then = screenout to exclude participants
• Using Variables: access responses in logic conditions
• Staircase Experiments: automated difficulty adaptation