We propose a new way of eyes-free interaction for wearables. It is based on the user’s proprioceptive sense, i.e., rather than seeing, hearing, or feeling an outside stimulus, users feel the pose of their own body. We have implemented a wearable device called Pose-IO (Figure 1) that offers input and output based on proprioception. Users communicate with Pose-IO through the pose of their wrists. Users enter information by performing an input gesture by flexing their wrist, which the device senses using a 3-axis accelerometer. Users receive output from Pose-IO by finding their wrist posed in an output gesture, which Pose-IO actuates using electrical muscle stimulation. This mechanism allows users to interact with Pose-IO without visual or auditory senses, but through the proprioceptive sense alone.
Figure 1: The main components of Pose-IO, the wearable device the enables Proprioceptive Interaction to take place.
We developed three simple applications that demonstrate symmetric proprioceptive interaction, where input and output occur through the same limb, as well as asymmetric interaction, where input and output occur through different limbs. In a first user study, participants using a symmetric proprioceptive interface re-entered poses received from Pose-IO with an average accuracy of 5.8° despite the minimal bandwidth offered by the device. In a second, explora- tory study, we investigated participants’ emotional response to asymmetric proprioceptive interaction and the concept of the user’s body serving as interface. Participants reported to enjoy the experience (mean= 4.6 out of 5).
Figure 2: (a) Proprioceptive interaction allows users to interact eyes-free based on their sense of proprioception alone, allowing this user to rewind a video, while maintaining eye contact with his audience. (b) The user is wearing our proof-of-concept bracelet called Pose-IO. (c) It reads input by sensing the same wrist’s flexion using an accelerometer and (d) it sends output to the user by actuating the user’s wrist using electrical muscle stimulation.
What is proprioceptive interaction?
Figure 2 illustrates the concept of proprioceptive interaction. Proprioceptive interaction allows for input and output by posing one of the user’s limbs, here the user’s wrist. Users enter information by performing an input gesture, here flex- ing their wrists inwards. The device senses this using its accelerometer. Users can perform such a gesture eyes-free, as their proprioceptive sense informs them about the position of their wrist. Users receive output from a proprioceptive interface by finding their body posed in an output gesture, here again the wrist. Also, they perceive this eyes-free by means of their proprioceptive sense.
Figure 3: Symmetric proprioceptive interaction revolves around the pose of one of the user’s limbs, here the wrist.
The interaction shown in Figure 3 is of the “purest” form in that input and output occur through the same limb, here the wrist. This “symmetric” interaction results in a particularly intuitive interaction. However, proprioceptive input and output may also occur through different limbs, e.g., when the application requires more input than output or more output than input. We call this asymmetric proprioceptive interaction, which is depicted in Figure 4.
Figure 4: In an asymmetric proprioceptive interaction, input and output occur through different limbs.