One of our current projects in the lab is the StressBot, a friendly console that can read heart activity through the Pulse Sensor to understand whether or not a person is in the physiological state of stress, and then offer coaching exercises and feedback to reduce stress through breathing exercises. We’ve been continuously testing our setup with research participants to try to create an interface that’s clear and accessible to anyone in our studio who might approach the device.
Since the last time we posted about this project, we have learned much more about correlating stress to heart rate. Joel Murphy, the creator of the Pulse Sensor, has helped us understand IBI (Interbeat Interval, or the time that passes between each heartbeat) and released some code that helped us grasp ways to map heart activity to stress. We have been using IBI measurements and the amplitude function Joel created to assign a specific value for stress, allowing us to measure whether it is relatively high or low.
Most of our previous prototypes focused on trying to match a visual pattern with the heart rate. This proved to be very complicated, and worst of all, stressful. We also found that having one’s eyes closed is often the best way to achieve a state of relaxation. After a few iterations, we discovered that audio feedback the best way to provide helpful feedback to a person who is trying to relax. This allows the person to close his or her eyes, and focus on finding a constant tone rather than something visual. The image above shows the first trial involving mapping the amplitude of the heart rate to the amplitude of a sine wave, and the IBI to the frequency of the sound. The upper most waves are showing the sound and the lower most wave is displaying the heart rate signature.
Below you can see the various explorations of mapping the same sound wave that is being altered by the user’s heart rate to another visual cue. The concentric circles show a rippling effect based on the IBI change, and the droplets are another way of visualizing the same sonic effect. The user in this case is trying to reach uniformity in pattern, either through the distance of the concentric circles or the distance and shape of the drops.
Below you can find the latest iteration of the interface. Using the screen and physical enclosure, the device acts as a coach character to help people know how to approach it and use the interface. It helps engage users with their bio signals, while providing the bot with the signification of the IBI state and a visual cue to ensure them that they are on the right track. Although the project is not complete, we are getting close! Our next steps involve experimenting with parameters, and doing more user testing.