Paper presented at the NordiCHI 2020 conference.
Algorithms are present in many of our everyday activities. However, there is generally low awareness of their presence among users, and there are various conceptualizations to define them. Additionally, algorithms are often both complex and opaque. These characteristics raise challenges when applying co-design activities to the interaction design of algorithms. We argue that researchers can overcome these challenges by developing sensitizing activities: activities that foreground the presence of algorithms, thus raising algorithmic awareness and a shared understanding, without influencing their initial experiences and expectations. We share how we applied sensitizing activities in two case studies: sensitizing interviews, and diary studies together with two-phase workshops. We share our experiences applying these techniques to overcome the challenges of low algorithmic awareness and multiple algorithmic understandings of participants. Finally, we offer recommendations for researchers and practitioners when applying sensitizing activities in this design context and invite further methodological discussion on this challenging topic.