Software or wetware?

Our lives are full of memorable and important moments, as well as important items of information. The last few years have seen the proliferation of digital devices intended to support prosthetic memory (PM), to help users recall experiences, conversations and retrieve personal information. We nevertheless have little systematic understanding of when and why people might use such devices, in preference to their own organic memory (OM). Although OM is fallible, it may be more efficient than accessing information from a complex PM device. We report a controlled lab study which investigates when and why people use PM and OM. We found that PM use depended on users' evaluation of the quality of their OM, as well as PM device properties. In particular, we found that users trade-off Accuracy and Efficiency, preferring rapid access to potentially inaccurate information over laborious access to accurate information. We discuss the implications of these results for future PM design and theory. Rather than replacing OM, future PM designs need to focus on allowing OM and PM to work in synergy.