Signal-contingent studies involve the use of a signal after which the participants respond to questions. Signal-contingent ESM studies request participants’ reports at varying times each day. Signals can be given by a beeper or a notification on the phone. Not only the device but the intervals should be considered: fixed times, regular repeating times, random times, or semi-random times. Signal-contingent designs are great for measuring constantly changing variables, such as depressive mood or fatigue. However, studies should not last for more than 1-2 weeks as they might become too burdensome for the participants.
As signal-based studies depend on many factors, such as the frequency of signaling, the duration of the signals, and of course, the length of the study itself, we should go into detail and explain a little bit more about the signal-contingent method. First of all, researchers should consider the main aspect of each ESM study: their participants and response rate. Note that in studies where participants were signaled 1-2 a day, the response rate was around 95%. In comparison, studies with signals more than eight times a day showed that participants tend to respond less, with a response rate ranging between 60% and 80% (Conner Christensen et al., 2003). The duration of the ESM study is also crucial for the design and the planning of all signaling procedures. If your testing forms require more than 3 minutes, do not expect people to fill them out more than six times a day as you’ll easily reach the burden cap in ESM research.
Also, consider all plans for any statistical analysis you may compute. Snijders and Bosker (1999) suggest that one can compute a multilevel power analysis to predict the number of cases necessary to measure within-subjects variance. Do not forget that the statistical power of the ESM study is a major factor to consider.
Interval-contingent reporting requires participants to respond at certain times every day. In other words, interval-contingent studies require reports at the same time each day. This design is perfect for routine activities (e.g., how much water one drinks), or things that are easy to remember. As they don’t require too much time or effort, these studies usually last about 1-2 weeks. However, some researchers worry that such studies are focused on a particular context. Let’s say that you test participants only at 10 A.M. when they are at work. Subject A shows higher levels of depression, while subject B seems more relaxed. So here researchers might face a problem: Can we implement these findings into everyday life and family life, for example? Is subject A always more depressed? We can’t be sure, so instead of making fake generalizations, we should consider combined methods that might be helpful.
Note that daily diaries are a type of interval-contingent study, with answering questions once a day, mainly at the end of the day. This is a great option for asking reflective questions. Studies using daily diaries can last longer as they are not so demanding, they last even about 1-4 weeks. We’ll present a daily diary study at the end of the guide.
Event-contingent ESM studies require participants to respond to questions related to a certain event (for instance, smoking) (Moskowitz & Sadikaj, 2011). They are applied to social interactions, anger management, incidents of conflict, and stress. This ESM design is the most reliable option for special events, which are not frequent. Thus, these studies can last longer – from 1 week to several months. As events are unpredictable, signaling schedules are not needed. However, some researchers find it beneficial to signal participants just to remind them to respond (Cote & Moskowitz, 1998).
Continuous reporting involves monitoring research variables all the time. Although this method can be employed for studying some factors over short periods of time, it is generally used for physiological variables, such as heart rate or temperature. This design can require a lot from participants or can generate large amounts of data (especially when it comes to passive reporting, such as heart rate). Thus, studies that rely on this design usually last not more than a week.
As mentioned above, another alternative is to combine some of these schedules. For instance, one might combine event-contingent reports with a time-based schedule (Shiffman, 2007).
In a nutshell
To sum up, let’s present the pros and cons of the three main scheduling methods: event contingent, signal contingent, and interval contingent, as systematized by Fisher and March (2012).
Interval-contingent schedules can be conducted with simple technology. Paper-pencil or computer, this type of research allows the use of various reporting methods. Also, as participants know which times of the day they are expected to respond, they might find this method less frustrating when compared to other ESM studies. However, as mentioned earlier, as interval-contingent studies focus only on certain times, they might miss some crucial information about people’s feelings, behaviors, and experiences that happen at other times. A suggestion for researchers is to use a signal just as a reminder throughout the day. In addition, to avoid memory decay, have participants report morning experiences reported at noon, for example.
Signal-contingent reports capture momentary changes and experiences without memory decay and even ten signals per day might be used in signal-based ESM studies. However, the unpredictable side of the signaling methods might become too burdensome to participants, and also the presence of some kind of signaling technology can be ineffective and even unappropriated (for the workplace, for example). A suggestion for researchers: design the given signals by basing them on the time it takes for each variable to fluctuate.
Event-contingent reports focus on certain events and also eliminate memory errors. However, researchers have no control over the reporting methods. Let’s say that a participant decided to light a cigarette without reporting the event. How can you know about it? Well, a tip is to train participants to recognize which events should be reported and motivate them. As mentioned above, remuneration should be considered.