Screener then branch

Ask one eligibility question up front and end the session for participants who do not qualify.

When to use it

Use this when eligibility can be settled by a single question and ineligible participants should leave before investing any time, for instance colour vision checks ahead of a colour task. Screening at the analysis stage instead wastes participants’ sessions and your recruitment budget, and relying on panel filters alone leaves you with no record of your own. Asking once and ending the session on a disqualifying answer keeps the sample clean at the door. If eligibility is already in the registration data, branch on a participant variable and skip the question entirely.

Trial file

type	content	head	responseType	responseOptions	required	if	then	stimFormat	stim1	keyboard	key	button1
form		Do you have normal or corrected-to-normal colour vision?	radio	Yes;No	1	responseCode=2	end
instructions	The colour naming task begins now.											NEXT
test								word	RED	r g	r
test								word	GREEN	r g	g
test								word	RED	r g	r

How it works

The opening row is a one-question form page: head asks the question, responseType radio renders it as radio buttons, responseOptions supplies the Yes;No choices, and required forces an answer before the page can be submitted. Form trials run conditional logic like any test trial, so the branching lives on the same row: if holds responseCode=2 and then holds end.

responseCode counts positions in responseOptions in the order you wrote them, so code 2 is No. A participant who picks it hits the end destination, which finishes the experiment on the spot; everyone else falls through to the next row and starts the task. Branching on the code rather than the answer text keeps the check stable if you later reword the choices, but remember the codes follow the written order, not the displayed one, if you ever add responseOptionsRandom.

Note the responseType value is matched case-sensitively: Radio would silently render display-only text with nothing to answer.

Variations

• Say goodbye before ending: point then at a label on a polite final screen instead of end; place that row last so the session finishes there naturally, and mind that a misspelled label silently continues to the next trial.
• Hand ineligible participants back to a panel: a then destination starting with https:// redirects immediately, with %%url_x%% placeholders filled from the study link’s query parameters.
• Screen on participant details instead of a question: an if such as %age%<18 compares the registered age directly, no form row needed.
• Branch several ways: pair ;-separated conditions in if with ;-separated destinations in then; one extra destination at the end acts as the fallback when nothing matched.