Prospective memory is memory for actions to be performed in the future such as remembering to give a message to a friend, remembering to take medication, and remembering to turn off the oven. It has often been contrasted with retrospective memory, which is memory for past events such as memory for a list of words learned in an experiment, memory for the plot of a recently seen movie, and memory for the names of former teachers. Interestingly, until the last 15 years or so, nearly all memory research focused on examining retrospective memory.
Although there are potentially many interesting dimensions along which prospective memory and retrospective memory tasks differ, our focus has been in understanding the differences at retrieval. A characteristic of explicit tests of retrospective memory is that the experimenter at some point puts the participant in a retrieval mode (Tulving, 1983) and directs participants to retrieve previously experienced episodes. By contrast, prospective memory requires that at some point in the future, individuals remember to perform an action without being put in a retrieval mode by an external agent. A typical paradigm for studying prospective memory, for example, involves asking participants to remember to press a key whenever they see a particular target item in the context of an ongoing task (such as rating words for pleasantness). Here participants are not explicitly asked (e.g., by an experimenter) to search memory when the target event occurs. Thus, when a prospective memory target event is encountered, attention needs to be switched from seeing the item as an item to be rated to thinking about the item as a cue for an intended action.
My long-term colleague, Mark McDaniel, and I believe that we use multiple processes for prospective memory retrieval with some being relatively automatic and others more consciously controlled. The major goal of our research over the past 15 years or so has been to understand (1) what processes we use to remember to perform actions in the future, (2) how these processes can break down in important real-world situations (e.g., an air traffic controller forgetting to reroute an airplane), (3) how these processes are affected by normal aging.