Permalink
Fetching contributors…
Cannot retrieve contributors at this time
79 lines (50 sloc) 5.46 KB

Using external survey tools with psiTurk

With the magic of iframes and javascript window messaging, you can integrate external survey tools into your psiTurk experiment. This is possible as long as the survey tool allows custom javascript to be triggered.

Window messaging allows cross-domain messaging via javascript, without having to configure security settings on the server. MDN says it best:

"The window.postMessage method safely enables cross-origin communication. Normally, scripts on different pages are allowed to access each other if and only if the pages that executed them are at locations with the same protocol (usually both https), port number (443 being the default for https), and host (modulo document.domain being set by both pages to the same value). window.postMessage provides a controlled mechanism to circumvent this restriction in a way which is secure when properly used."

Three special steps to hook up your survey to psiTurk:

  1. Embed your survey as an iframe within one of your psiTurk pages or views.
  2. Add a message event listener to your psiTurk window
  3. Post a message from the survey tool to the window.top when the survey is complete. window.top will be your psiTurk window. Do whatever you want via javascript once you receive the expected message.

To tie the psiTurk data and the external survey data together, embed a unique id into the iframe url you load, and then record that unique url into your survey data. Don't forget to do this. If you forget, you won't know to who to connect your survey data. If you want to tie things both ways, post back your survey session id as part of the survey-complete post-back.

An example with Qualtrics

As of the time this documentation page was written, Qualtrics has an undocumented "feature". Qualtrics automatically posts a window message to window.top when the Qualtrics "end of the survey event" is triggered. For Qualtrics surveys embedded as iframes in psiTurk experiments, we can take advantage of this behavior. The Qualtrics-posted message contains your survey_id and the participant's Qualtrics-created unique session_id. You should already know the survey_id (because you just embedded a link containing this id), but the session_id is Qualtric's unique id for whoever just finished your survey. You can record that with psiTurk as unstructured data (see :ref:`recording-unstructured-data-label`) if you desire.

Don't forget to explicitly log the psiTurk unique id as embedded data within Qualtrics. See here for more about embedding data into Qualtrics surveys.

The posted message when they finish a qualtrics survey is a string that looks like this:

QualtricsEOS|<survey_id>|<qualtrics_session_id>

So you can do something like this on your psiTurk page:

// load your iframe with a url specific to your participant
$('#iframe').attr('src','<your qualtrics url>&UID=' + uniqueId);

// add the all-important message event listener
window.addEventListener('message', function(event){

    // normally there would be a security check here on event.origin (see the MDN link above), but meh.
    if (event.data) {
        if (typeof event.data === 'string') {
            q_message_array = event.data.split('|');
            if (q_message_array[0] == 'QualtricsEOS') {
                psiTurk.recordTrialData({'phase':'postquestionnaire', 'status':'back_from_qualtrics'});
                psiTurk.recordUnstructuredData('qualtrics_session_id', q_message_array[2]);
            }
        }
    }
    // display the 'continue' button, which takes them to the next page
    $('#next').show();
})

This code can be put on a page that has a link with id #next default-hidden via css which advances the participant to the next experimental page. Note that this code checks that the event is QualtricsEOS before continuing on. That's because Qualtrics posts other events to window.top, too. This code is only interested in the EndOfSurvey event.

Also notice that this code doesn't implement any security precautions. Normally it's good practice to check to see where a message is coming from before you act on it. For instance, it might check to verify that the message is coming from a qualtrics.com domain. But in this code, the worst-case scenario is that a tech-savvy participant somehow triggers that they completed the survey before they actually did. In that case, their survey data would be blank, and after visual inspection their assignment could be rejected.

What about not-Qualtrics?

If your survey tool isn't posting messages to window.top for you, just window.top.postMessage(<message>, <targetOrigin>) yourself. For instance, you might have javascript in your survey tool that does:

window.top.postMessage("all_done|<survey_session_id>","*")

Then just listen for that event back on your psiTurk page, as in the Qualtrics example above.