the design of many lifelogging user interfaces) that place, events, and people are stronger cues than time. 5 Other research has found that cues can trigger inferences about what must have happened in someone’s life, rather than genuine recollection23; for example, a photo showing us having lunch with friends may cause us to truly remember the event or simply lead us to conclude we must have been there. Finally, while recollecting the past is highly dependent on the kind of cues presented to people, for prospective memory ( memory for future events and intentions), the important issue is not so much the type of cue but rather when a cue is delivered, allowing an intention to be remembered at the right time and place. 24 This observation suggests that the capture of data (such as location or other contextual cues) might be used to trigger reminders rather than provide content to be remembered.

These observations run counter to much of the rhetoric surrounding lifelogging, where such phrases as “digital memories” and “experience capture” are often used. They show instead the importance of understanding the precise relationship between the cues we are able to capture through lifelogging technologies and the memory experiences they trigger, with clear implications for how we might design improved systems.

Support for the Five Rs. Most lifelogging proponents presume that the systems deliver benefits without being specific about what the benefits might be, assuming a one-system-suits-all approach. As we outlined earlier in the section on lifelogging benefits, the psychological literature distinguishes many different types of memory, each involving different retrieval processes. Thus, it is not simply a question of what the system captures but determining how such a system would be used. This determination depends largely on the type of memory being targeted or, more generally, the kind of benefit system designers hope to deliver to end users.

Many total-capture systems implicitly seem to address recollection, or remembering past personal experiences. It is well known in the psychological literature that there are strong connections between these autobiographical memories and visual images. 8 This

systems supporting
reminiscence and
reflection have
received far less
attention than
those supporting
recollection and
retrieval.

suggests that the interfaces for such systems should focus on images as the backbone of their design. In contrast, systems for retrieval need not be concerned with recollection, but rather with efficient ways of searching though large heterogeneous collections of data and so provide access to metadata that might support effective search. If system designers decide to support reminiscence, other kinds of factors become important (such as optimizing the sharing of data with others). Systems for reflection might be different still where abstraction is important, offering flexible and novel methods for viewing personal data in ways that might surprise, provoke, or educate users. Finally, designing systems to support remembering intentions need to focus on delivering timely cues in appropriate contexts if they are to provide effective reminders.

Applying such memory taxonomies is vital for designing effective systems. First, they clarify the aspects of memory the systems are trying to support; without such clarification it is difficult to know whether the systems succeed. Second, understanding the relevant psychological processes allows designers to create systems to better support the processes. Third, taxonomies can suggest new directions for exploration; for example, systems supporting reminiscence and reflection have received far less attention than those supporting recollection and retrieval.

Offloading and metamemory. Much of the lifelogging approach is motivated by the observation that human memory is fallible. Lifelog proponents argue we need to remove the memory burden from humans, offloading it to reliable and comprehensive external digital stores. These claims need careful scrutiny, as we calculate the costs associated with digital archives, even if they make it possible to store vast amounts of data. For example, the effort required to capture, create, and maintain some kinds of data can be prohibitive. Moreover, accessing data can be inefficient compared with exploiting “organic” human memory.

How, when, and why people exploit external memory tools has been studied extensively in the psychological subfield of metamemory, 6 which addresses people’s understanding of the strengths and weaknesses of their