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Ten Step Stroop Experiment

  • Overview
  • 1. Create an Experiment
  • 2. Add a Consent Form
  • 3. Add a Bot Check
  • 4. Set up a Branch Node
  • 5. Reject Unwanted Participants
  • 6. Set up a Randomiser
  • 7. Create Fixation Time Manipulation
  • 8. Add Two Stroop Tasks
  • 9. Preview and Commit
  • 10. Choose a Recruitment Policy


To link your tasks and questionnaires together and send them out to participants, you’ll need to use our experiment tree.

This walkthrough is designed to follow the Ten Step Task Stroop Walkthrough, so we recommend completing that first!

If you haven’t followed the task walkthrough, you’ll need to create a project before continuing this walkthrough. Click here for instructions.

If you have followed the task walkthrough, go ahead and open your Stroop project in a new tab and you're ready to start! You can find your projects here.

1. Create an Experiment

First, create a new experiment inside your project. New experiments come with a start node and a finish node. Nodes are the building blocks of Gorilla experiments: you can find a full list on our support pages, here.

2. Add a Consent Form

Most experiments start with a consent form. Gorilla has a pre-made consent form example, which we’re going to add here. You can of course also create your own questionnaire, or clone and edit our example.

3. Add a Bot Check

Next, we want to check that our participants are real people who are paying attention to our experiment! To do this, we’re going to use one of Gorilla’s pre-made bot checks: an easy visual search task, where participants have to click on the picture of a cat among many pictures of dogs. We’ve called this a bot check, but it also serves as an attention check for genuine participants. You can find more ready-to-use bot checks on our samples page.

4. Set up a Branch Node

Once participants have completed the bot check task, we want to branch them based on whether or not they answered correctly. Gorilla makes it easy to branch participants - you just insert a branch node! The bot check task is already set up to record correct answers, using embedded data, and it includes 2 questions.

All we need to do here is set up one branch for participants who got 2 answers correct, and another for participants who got less than 2 answers correct.

If you want to store any information during a Gorilla experiment to use later in the experiment, you'll want to use embedded data. You can learn more here.

5. Reject Unwanted Participants

If participants fail the bot check, they’re either bots or people who just aren’t paying attention. Either way, we don’t want them to take part in our experiment, so we’re going to use a reject node to reject them! If you reject a participant before they finish your experiment, you’ll get their participant token back so that another participant can use it. If you'd like, the reject node will also let redirect rejected participants to another webpage.

If you want to screen your participants in other ways, for example recruiting only over 50s, or only people who are bilingual, you can use the branch and reject nodes in the same way.

6. Set up a Randomiser

Now we’re happy that all our participants are genuine and engaged with our experiment, we’re ready to move on to the main part of our experiment, the Stroop task.

We’re going to investigate whether there are differences in performance between 2 versions of the Stroop task: one with a long fixation time, one with a short fixation time. To do this, we want to randomly assign each participant to one of two conditions, using Gorilla’s randomiser node.

7. Create Fixation Time Manipulation

We want to create 2 versions of our Stroop task, with different presentation times for the fixation cross. To do this, we need to set fixation cross presentation time up as a manipulation in the Stroop task. Use the Stroop task you created in the Ten Step Task Stroop Walkthrough.

To learn more about manipulations in Gorilla tasks, see our task builder FAQ, here.

If you haven’t completed the task walkthrough, click here for instructions on adding a pre-made Stroop task to your project.

8. Add Two Stroop Tasks

Now we’ve set fixation time up as a manipulation to our Stroop task, we want to add two versions of the same task to our experiment. One will have the default fixation time we set and one will have a longer fixation time.

9. Preview and Commit

And that’s our experiment completed! Time to preview it to check we’re happy, and then commit it.

Note: at the end of the preview, you'll have the option to download your data. We strongly advise that you check you're happy with the data you receive before starting to recruit participants.

10. Choose a Recruitment Policy

Once you’ve committed your experiment, you can send it out to participants. There are lots of different recruitment policies you can use in Gorilla, but we’re going to use the most straightforward: the simple link.

For more information about recruiting participants and collecting data, read our guide to recruitment and collecting data.

In order for participants to enter your experiment, you'll need to have purchased participant tokens. We offer different pricing options to suit everyone, from pay-as-you-go to department and institutional subscriptions. You can see our pricing page here.

If your university already has a subscription, you can see how to join a subscription here, and how to request tokens from your subscription here.

Once you've added tokens to your account, you're all ready to start recruiting participants. Happy experimenting!