Thinking about a one-way mirror

One-way mirrors are elements of films, TV shows and usability laboratories.

A one-way mirror (or a two-way mirror, depends on who you ask) is a permanent tool for interrogations, psychological experiments, focus groups and usability tests.

A one-sided mirror is a special piece of glass , illuminated on one side to allow people to be watched while on the other side of the glass.

This technology, in fact, is quite old and coming from the "transparent mirror" , patented in 1903.

Researchers once decided that a one-way mirror was necessary in the work, but in the past few years I have seen that companies are moving away from using it. Here are some of the advantages and disadvantages of a one-way mirror.

Benefits

• Overview: By observing from the right angle you can see the entire room in context and, thus, cover all relevant information, such as the participant’s emotional expressions and interaction with the curator. The overview is especially valuable when you observe the interaction of participants with physical objects (for example, setting up a TV) and their movement around the room.

  
  

• Low manufacturability: One-way mirror does not require much maintenance after installation (it does not require electricity, cables, converters).

  
  

• Cool looks: The reason for appearing in one-way mirrors in movies and TV shows is that they look cool! They were one of the main objects on excursions in the lab when I was working at Oracle. If you have a one-way mirror, you at least look like a serious researcher.

  
  
• Better than a room full of people: Watching through a one-way mirror is better than having a crowd of people crowding the room with a participant or looking over the participant’s shoulder. This is also a less distracting factor for the participant, as observers do not walk around and do not chat.

disadvantages

• Frightens off some participants: One-sided mirrors are hardly a tactful subject, but participants usually know their goals (they watch TV and movies too!). By some people, they are perceived as "frightening, nerve-killing, and uncomfortable." Such perceptions can influence the behavior of the participant , even though in order to understand the effects, if any, you need as much data as possible.

  
  

• Limits the view: It can be difficult to see the participant’s computer screen while behind the mirror. What is happening on the screen is the most interesting for observers in a usability testing session. Consequently, observers, ultimately, look at what is happening on the participant's monitor. Which can be sent to anywhere in the world. In fact, much of what you can get from a one-way mirror can be obtained with well-placed cameras and a direct stream from computer monitors.

  
  

• Requires a large allocated space: To work with a one-way mirror, you need a viewing room adjacent to the laboratory. This usually requires the allocation of large space, which in many urban areas costs substantial money.

  
  
• Increases noise and light pollution: Being close to the participants and watching them through the mirror means that the observers are forced to talk more quietly (no laughter and loud conversations) and keep the observation room in the dark. The absence of observers in the room with the participants reduces distractions, but not completely. Open doors, turned on computers and telephones generate light and allow participants to see the observers, which can create an awkward position for the participants and this will distract them.

Is it true that a mirror affects behavior?

Each research team must weigh the practical advantages and disadvantages of a one-way mirror. But one of the questions to consider is “To what extent does a one-way mirror really affect the behavior of participants and how much can it affect your research findings?”.

When we looked into the literature, we found a little discussion about how a one-way mirror affects behavior and some research into the effects of the mirrors themselves. After that, when the participants looked in the mirror, they began to look at themselves, which has consequences. We found that mirrors increase self-awareness, which leads to:

• Decrease "deceptions when solving puzzles" ; children were more altruistic
• Increased negative emotion reporting [pdf]

How a one-way mirror can affect data from usability tests, in-depth interviews or focus groups is still an open question. Interestingly, I did not notice the difference in behavior between participants in experiments with or without a one-way mirror. Jim Lewis, based on his experience, also speaks about the presence of a small influence, but he cited a memorable example:

For more than 200 people I watched in those years, I only once encountered a participant who was so nervous that we sent her home. There was also a guy who was learning how to work with a printer. His job was to feed folded paper into the printer (remember this?) And straighten it so that the information was printed in the right areas. He was so upset about his task that one day he pulled the paper out of the printer, crumpled it up and threw it into a one-way mirror (by accident, there was no curator in the room). This is the only time I can think about someone coming to think about the observers while working on the task. In most cases, participants came to be completely absorbed in their task.

One-way mirror, a mirror on the wall ...

In our laboratory at MeasuringU, we have a completely digital set of equipment and decided that we are against using a one-way mirror (its disadvantages outweighed its advantages for us). But if you have a one-way mirror (or you are thinking of installing one ), then here are some of the best practices based on the experience of other researchers :

• Do not pretend that the mirror does not exist. Better to tell about its existence and explain its use. And do not forget to give a chance for participants to contact you with a problem.

  
  

• Think when you are moderating a session from inside the laboratory, and do not represent the voice of God , even though you need more research to understand the effects, if any, of the location of the curator.

  
  
• Arrange the participants so that they do not sit facing the mirror. This will reduce the chance that they will peer into the mirror and will remind them less of what they are watching.