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Longitudinal studies

In certain experimental designs, you may want to compare participants’ responses at multiple points in time. In such a design, participants may respond to the same ROLEG experiment multiple times or take part in different ROLEG experiments that belong to the same study. If you want to compare responses at different times by the same participant, you need to know which responses belong to the same participants.

We recommend using the following procedure in order to make sure that the linking of longitudinal data to the correct participants is compliant with privacy regulations:

  • The experiments that make up the longitudinal study should be public but not active. This way, only people with a direct link to the experiment(s) are able to participate.
  • Create a unique password for each participant. It is recommended you use an actual word instead of number to prevent mistakes. You are allowed to store a list of participants’ email addresses and corresponding passwords for the experiments on the RU filesystem (on the U-drive for instance). Make sure to delete this list after linking the data.
  • Include a textfield block in each experiment that prompts the participants for their unique password, see the code below for a reference implementation.
  • Send the link of the experiments to each of the participants and instruct them to enter their unique passwords when prompted.
  • Once all participants have participated in all experiments, download the results files and link the respective participants’ responses using the value for the correct textResponse variable in the result files.
experiment {
    trial {
        stimulus {
            text = "This is part 1 of a longitudinal study. Please enter your unique password below."
        response {
            textfield {
                placeholder = "Enter here"

    // Rest of the experiment...
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