Experiment recruitment: Why people don’t turn up

If you have run experiments with people as part of your research, you’ll know that recruiting participants can be a tough job. Even trickier is maximising the likelihood that those participants will actually show up to their assigned slot. It’s no fun to wait all day for participants that never arrive.

In the past year, I have run two experiments where I’ve had to recruit student participants. In the first, a pilot study (which is like a smaller, practice, dress-rehearsal style study), lots of people signed up, but quite a few failed to turn up to the session. In the second, I put a number of plans in place to make sure that didn’t happen again. SPOILER: Those plans worked pretty well.

And so, I am presenting you with two posts, which will hopefully prevent any of you from sitting in an experimental room alone and participant-less. Today’s post will look at what stops people from turning up to experimental sessions. The next will give some advice on what you can do about that.

Why don’t people turn up?

When a participant doesn’t arrive for your study, a number of potential reasons swirl through your head. Are they late? Did you give them the wrong time? Has something awful happened? The first time I had two no-shows in a row, I wondered if some sort of portal to another world had opened up outside of the building. This was probably overly dramatic.

In reality, it seems like there are two main reasons for why people fail to come to experimental sessions:

1. They forget

It’s easy to forget something if it isn’t written down in the place where you need to see it. Even if it is written down, the piece of paper may be lost, or the online calendar may not synchronise properly. These things happen. The blame for forgetting doesn’t fall solely on the participant’s side – if you (as the experimenter) don’t contact them to confirm their slot, they may never consider it a firm arrangement.

2. Something else comes up

Reasons for participating in experiments vary: Sometimes it might be purely out of interest, or altruism, but more often than not (especially with a student population), it’s because of the compensation that’s received after the experiment (usually vouchers or cash). But sometimes things will come up that are more important than that money.

Say, you’re going to get £7 for an hour. But then you realise that you’re late with your coursework. You need that hour more than you need £7. So you don’t turn up.

The problem with this is that it doesn’t take into consideration how important that hour is for the experimenter.  The room may only be available for a limited amount of time, and all the participants have to be seen in that time. Fewer participants mean that working with the data might be more difficult, and it may not be possible to use the tests you’d originally planned.

Why don’t people tell you they’re not going to turn up?

As an experimenter, I have no problem if someone wants to cancel their session. If someone gets in touch in advance, and says they will no longer be able to attend, there are zero hard feelings. I don’t even need a reason. Obviously, the more notice is better. That way you can arrange for another participant to come instead. It’s not great receiving a cancellation email or text two minutes before the allotted time. But you know what, it’s so much better than never receiving any correspondence at all. At least, then, you can do something with that experimental slot, rather than sitting, nervously, wondering if someone is going to arrive twenty minutes late.

So why don’t people just tell you they can’t make it?

1. They forget

Look, if they’ve forgotten the experiment was even happening, they’re probably not going to remember to let you know. However, if they remember at the last minute…

2. They are pretending it isn’t happening (out of sight, out of mind)

It’d be pretty embarrassing to forget about an experiment until the last moment. There is the worry that if you contact the experimenter, you’ll receive a message in return, rebuking you for your behaviour. It may seem easier to just pretend that it isn’t happening. Similarly, even if you have plenty of notice to cancel, you may be wrestling with your decision to do something else instead. It may feel like you’re letting someone down, and maybe you should still go to the experiment. But things slide, and you can’t make it. And by then, it’s too embarrassing to get in touch. And thus, an empty experimental slot is born.

Next time…

We’ll look at some methods I used to keep my experimental schedule as full as possible, and to minimise no-shows…