Institute for Language Sciences Labs


Recruiting adult participants

Last updated on 11 July 2023 by Iris Mulders

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This howto details how to go about recruiting adult participants in the ILS Labs. If you would like to participate in an experiment yourself, as a participant, see our website for participants.


Recruiting subjects on-line: Who can use the ILS adult participant database?

At ILS Labs, an ever-growing list of email addresses is available of people who have indicated that they want to receive invitations to participate in experiments at the institute. These participants regularly receive emails to sign up for experiments at the experiment homepage.

Use of this mailing list is limited to ILS experiments where participants are paid for participation. For issues surrounding participant payment, see this FAQ.

You can make use of our on-line subscription system, if

  • you are an ILS researcher, and
  • you have secured money to pay the participants, and
  • the type of participants you are looking for is available in the ILS participant database.

How many and what kind of participants are in the database?

Most of the people on the participant mailing list are students or recent graduates of the Humanities faculty. These are mostly non-dyslexic native Dutch speakers (we do have some dyslexics on the list though).

About 80% of the list is female. If achieving a gender balance is important for your experiment, you will need to take special measures. (About 90% of the participants who sign up are female, and male participants are more likely to not show up).

There are over 1000 participants on the list. The email addresses and any personal details the participants provide are, of course, confidential information.

The number of participants that can be recruited through the mailing list depends on various factors, – if you have strict exclusion criteria it’s more difficult to find people who meet your criteria of course, and vacation or exam time make it more difficult too. But for most experiments, recruiting up to 100 unique (mostly female) participants is fairly easy.

If you are looking for ‘special’ participants, like elderly people, or people with another language than Dutch as their native language, the ILS participant mailing list is not going to be useful for you; you will need to do your own recruitment. For special language groups, try Facebook, google groups, or specific hangouts (churches, expat organizations etc). For scheduling these participants, you can ask for a subscription form to be hosted on the ILS participant recruitment homepage (see below). But usually it is easier and more effective to convince people to participate through personal contact.

If you need to recruit infants for an experiment, contact Desiree Capel.

How does on-line subscription work for the participant

The experiment homepage gives an overview of all the experiments that participants can currently sign up for, as well as some general information. When participants are invited to sign up for a specific experiment, they receive a link to the subscription page for that experiment.

On the subscription form, the participant can pick a time slot and provide contact information and information required to determine whether they can participate in the experiment. The form always asks for name, phone number, email address, date of birth, native language, mono-/multilingual, biological sex, right/lefthanded, dyslexic/not dyslexic, and social role (student/not student).

The participant will get an automatic confirmation over email. In this email, they also receive a link where they can unsubscribe from the experiment as long as the time slot they subscribed for is still in the future; if they are logged in on the website, they get an overview of the time slots that they have subscribed for, or if they don’t have an account, they will receive a link that is valid for two hours where they can do the same. If they unsubscribe from your experiment, you will receive a notification over email.

Participants can also make an account on the system; the advantage of that for them is that they don’t have to repeatedly fill out information that we already have about them, and that they can easily see an overview of all the experiments they participated in (with a possibility to unsubscribe for timeslots that are still in the future).

Online experiments

This howto assumes that you will be running your experiment on location in the lab, but you can also use the recruitment system to recruit participants for on-line experiments. Contact Iris Mulders for more information.

What kind of information do you need to supply to make use of the on-line subscription forms

Provide this information about a week in advance, so that the timing of the invitations to participants can be coordinated with other experiments. Hashing out the details of your form (criteria) may take a few back-and-forths, too. The actual invitations to the participants will only be sent when you are 100% ready to run (see below), but this should not stop you from requesting the subscription form well in time.

Information required to create a subscription form

FEtC-H approval

Your experiment may need to be approved by the FEtC-H (Faculty Ethics assessment Committee – Humanities) before participants can be recruited. For more information, see the FEtC-H website.

Experiment details

This is the name that will be shown on the website. The more memorable, the better; the purpose is to give the participants something they can remember by whether they’ve already participated or not. Some imagery from a filler or practice item usually works well. Examples from past experiments: 'Sailors with painful necks', 'The doctor has pineapple'.
The standard amount is 10 euros per hour, usually with a minimum of 5 euros for experiments shorter than 30 minutes. See the howto Arrange money for participants.
Participants like to know what they can expect; please fill this field out in Dutch if you can!
Is your experiment run in person on location in the lab, or online?
Be exact!

Experimenter(s) details


One of the experimenters has to be the contact person for this experiment. This person's phone number and e-mail address will be provided in the confirmation message to the participants when they subscribe.
The phone number of the lab you will be testing in will also be added (except for K.13 and K.07, where incoming phonecalls will disturb the participant).

In addition, the contact will be able to put timeslots on the form and to view/unsubscribe participants.

Additional experimenters

Add details for any other experimenters here. They will have the same rights as the contact experiment leader, so they will be able to:

  • log in to the system
  • put timeslots on the form
  • view and unsubscribe participants
  • send reminders to participants from the system
  • create comments for participants

They will also receive an email from the system when a participant unsubscribes from the experiment (but not when they sign up).

The only difference with the main/contact leader is that additional experiment leaders' contact details will NOT be sent to the participants when they sign up for the experiment.

Participant criteria

What are the criteria the participant should meet in order to be able to participate in the experiment?
The standard criteria are listed below; the most usual option is selected by default. Change this selection if you want to divert from it.
At the bottom a text area is provided where you can list any other criteria.

NB: some (not many) of the Dutch participants on the list are early dialect speakers (from Limburg etc). They will be in the database as native Dutch speakers; if you want to exclude them and test only speakers of standard Dutch (whatever that may be), indicate so below in 'other criteria'.
Note: to avoid consent issues with underage participants, it's a good idea to recruit only participants that are at least 18 years old.
For example, you may want to exclude participants who participated before in a certain other experiment (please indicate name of the experiment and in which month and year it was run, if you can). Or you may have other criteria. Please fill this field out in Dutch if you can, and be very specific about the criteria - vague criteria confuse participants.
If you indicate that you want to run, for instance, 3 participants at the same time, every timeslot you add to the form will actually make 3 timeslots for that one time, distinguished by 'werkplek 1', 'werkplek 2', and 'werkplek 3'.

How does it work for the experiment leader

Your solisID will be added to the recruitment system (or if you don’t have a solisID, an account will be created for you); you will receive a confirmation email. You can then log in with your email address and your (solis) password on the login page.

Once your experiment subscription form has been created, you will receive another email. You can then put the time slots on your subscription form yourself.

After logging in, you will see an overview of your experiments:

Example overview of experiments (screenshot, click to enlarge)

Use of the system is self-explanatory for the most part; do read the information below for pointers on the most effective and constructive way to use it.

Adding a photo of yourself

You can edit your details through the ‘Verander profiel/Change profile’ link in the black top bar. If you want, you can also upload a photo of yourself. The photo will be shown on the subscription form for your experiments, and may increase participant awareness that you are a real person who will be sad when they don’t show up 😉

Adding timeslots

Clicking on the clock icon clock will take you to a page where you can add timeslots to your experiment:

Adding timeslots, example (screenshot, click to enlarge)

Pro tip: enter the timeslots by typing them in the Datetime field, rather than by using the pop-up calendar – it is much faster.

To remove a timeslot, click on the garbage can bin_closed following it.

Don’t forget to also reserve lab space in the reservation system for the times you want to run participants!

For most experiments, your time slots will be fully booked within a day or so, provided the invitation is sent out a few days before you start running. Do make sure to add about 10-15% more time slots than you need participants, to compensate for no-show participants. Send your participants a reminder the day before their appointment (see below), otherwise you can easily get 25% or more no-showers.

If your experiment will run for more than two-three weeks, don’t put all the timeslots on at once, but limit yourself to only the first two-three weeks. If you put all the timeslots on in one go, you will get a lot of no-showers for the later slots; also when you add new timeslots later on, this is the perfect reason to send a new invitation to the mailing list.

Opening your experiment for subscriptions

Once you have added the timeslots:

  1. Make sure that you have run a technical pilot of your experiment on yourself and that it is 100% ready to run, technically. Check your data to make sure the output is what you need for your analysis!!
  2. Make sure that you have run a behavioral pilot of your experiment on some others, and again, check your data and analyze it to make sure you have everything you need!! (NB: To pilot your experiment, you are expected to find your own pilot participants. If this is difficult for you, contact Iris Mulders to discuss the best solution. Also, if your pilot participants are likely to be on the mailing list, let them sign up on your subscription form to prevent them from signing up once you start running for real (or from signing up for a follow-up experiment). Contact Iris Mulders to discuss).
  3. Verify that the time it took your pilot participants to complete the experiment is what you said for the subscription form (if not, this – and anything else – can still be changed).
  4. Make sure that you have arranged for money to pay the participants, and have printed a sign-off list.
  5. Make sure that you have approval of the FEtC-H and your consent forms are printed, ready for the participants to sign.
  6. If you are running in the lab, make sure that you have reserved lab space for the times you intend to measure participants.
  7. Make sure that you have made any other arrangements you need to make to run your experiment.

If you are 100% ready to run participants, you can return to the experiments overview page, and click the experiment closure icon to open your experiment for subscriptions; the icon will change to a check mark . Your experiment will now appear in the list of available experiments on the Experiment homepage for participants. On that page, click on your own experiment form and double-check that your timeslots are correct (and that you haven’t, for instance, put in multiple timeslots for the same time if you didn’t mean to).

Send an email to Iris Mulders to indicate that you are ready for the invitation to the mailing list to be sent out. Ideally, the invitation is sent out two days before you start running, but if necessary the day before can work pretty well, too. Note that invitations are not sent out on Fridays or Saturdays (since participant response is approximately zero on those days).

Viewing participant info and sending reminder emails

Click on the participants icon to see an overview of the participants who have signed up for your experiment. You will receive an email when a participant unsubscribes, but not when a participant subscribes. The participant overview is how you track how many participants are subscribed.

In this view, you can sort the fields by clicking on the name of the field; you can also limit the view to only certain participants by typing in a search box at the bottom. For instance, if you type 2022-10-07 in the ‘Date & time’ field, you will only see the participants scheduled for October 7, 2022.

This is convenient for sending reminder emails; limit your view to only the participants who are scheduled for tomorrow, then check the boxes in the ‘reminder’ field for the participants you want to send a reminder email; click ‘send’ to send the reminders. The participant will receive an email noting the time, date and place you are expecting them, and the contact info for the main experiment leader, so they can contact you personally in case they need to cancel with less than 24 hours notice. Note that while an experiment can have multiple experiment leaders, the participant will receive only the contact details of the main experiment leader. If you need to switch roles midway through an experiment, contact Iris Mulders.

Bear in mind that the participant’s information is confidential. Do not use email addresses for your own purposes. Do not share emails or any other participant details with other people (not even your close colleagues!). Do not leave a page with the details open on a public computer, for instance a lab computer. Do not leave printouts lying around.

How to deal with no-show participants:

  1. Call or email them to let them know that you’ve been waiting for them (sometimes they don’t realize there’s an actual person waiting for them).
  2. Add a comment to the participant so I can take them off the list if they make a habit out of not showing up. In the participant list, click on the talk balloon in the field ‘Actions’ for the participant in question and add a comment. You can add other types of comments there, too (to indicate lack of effort for instance, or resistance to instruction. The participant will not see your comment).
  3. After you have emailed/phoned and added the comment, unsubscribe the participant: either with an automated email or without . There are two good reasons to be disciplined about unsubscribing no-show participants:
    1. it keeps your overview up-to-date; this is important if you (or your supervisor) will want to exclude the participants in this experiment from participating in a later experiment
    2. it opens up the possibility for the participant to subscribe for a different time slot (they can only be subscribed for one time slot per experiment)

If a participant shows up later after all (after you have already removed them), make a new timeslot and let them sign up for it right on the spot, so that your list of participants remains up to date.

If a participant unsubscribes themselves through the system less than 24 hours before you were expecting them, a comment will be added automatically for them.

Tips, tricks and factoids

  • Click on ‘CSV’ (top left) to save your participants to a .csv file. Treat this file as confidential information. Delete any participant info from it that you don’t really need.
  • When you have finished running your experiment, close the experiment for subscriptions.
  • Privacy feature: some time after your experiment has finished running, the participant’s contact details will be set to be invisible for you. If you need to see the contact details, for instance to invite them to a follow-up experiment, contact Iris Mulders. You will be asked to not contact participants who have unsubscribed from the mailing list in the mean time, or at least be extra careful and apologetic if you do need to contact them.

Up to contents

If you find mistakes in this page or have things to add, please send them to Iris Mulders.