A Brief Introduction



Prospective memory is remembering to perform delayed intentions at an appropriate time or event in the future. Examples of prospective memory include: remembering to take medicine at night before going to bed, remembering to deliver a message to a friend, and remembering to pick up flowers for a significant other on an anniversary. Because a great deal of each day is spent forming intentions and acting on those intentions, it is no surprise that at least half of everyday forgetting is due to prospective memory failures (Crovitz & Daniel, 1984). 

Current research in the lab (with graduate student Francis Anderson) has also used experience sampling methods to show that thoughts related to planning and executing prospective intentions composes nearly 15% of all daily thoughts (see section below).

It is important to understand prospective memory not only because of the ubiquity of prospective memory demands, but also because prospective memory failures can be devastating. For example, aircraft pilots must remember to perform several actions sequentially prior to take-off and landing and failure to remember to perform any of these actions may result in injury or death. Although aircraft crew prospective memory failures rarely occur or lead to injury, Dismukes (2006) noted that almost 1/5 of major airline accidents can be attributed to prospective memory failures. Moreover, people who must remember to take medication depend upon their prospective memory for maintaining their health. In one survey (Nelson, Reid, Ryan, Willson, & Yelland, 2006), individuals who reported forgetting to take their blood pressure medication at least one time were significantly more likely to have a heart attack or die than individuals who did remember to take their medication. Because intention forgetting has the potential to be devastating, it is important to learn more about the strategies that improve prospective memory. To do so, a greater understanding of prospective memory must be obtained, with careful focus on how memories are retrieved. By understanding how intentions can be successfully retrieved, strategies can be formulated which will promote efficiency and functionality.

A central theme and the cause of major debate in the field has been understanding the mechanisms that allow prospective memories to be retrieved. The preparatory attentional and memory processes (PAM) theory argues that strategic, non-automatic preparatory processes must be engaged before the occurrence of a target event if one is to successfully retrieve an intention (Smith, 2003). Consequently, a prospective memory intention can only be successfully retrieved if the person engages in monitoring (scanning for the target event or maintaining the intention in mind) for his or her prospective memory cue. Furthermore, because monitoring is non-automatic and capacity-consuming, successful prospective memory should be associated with costs (slowing or errors) on the ongoing task.

Alternatively, the multiprocess theory (see McDaniel & Einstein, 2007 on publications page) argues that intentions can be completed not only via monitoring, but also by a relatively automatic spontaneous retrieval process. Introspectively, we experience this near-automatic process when memories “pop” into mind. Unlike the non-automatic preparatory processes that are required to monitor, the multiprocess theory argues that under appropriate conditions (see Einstein, McDaniel, & Anderson, in press, for conditions that encourage spontaneous retrieval) the appearance of a target can trigger remembering without incurring a cost on an ongoing task. Put simply, the idea is that an intention can be retrieved without keeping the intention in consciousness. For example, during a trip to the grocery store, simply seeing a jug of milk can cause retrieval of the intention that you are out of milk and need more! A major goal of research in this laboratory has been providing empirical support for the existence of spontaneous retrieval processes. In addition, we have been interested in the interplay between monitoring and spontaneous retrieval processes (Scullin, McDaniel, & Shelton, 2013) and in determining which factors lead an individual to rely on one retrieval mechanism over another (see McDaniel & Einstein, 2000).

Our Research


We are currently working on several lines of research in the lab, with the overarching theme of trying to better understand the underlying mechanisms of prospective memory, how those mechanisms play out in the real world, and how we can take that knowledge to improve people’s ability to perform intended actions.


As mentioned in the Brief Introduction, the multiprocess theory contends that intentions can be completed by both resource-demanding monitoring processes as well as relatively automatic spontaneous retrieval processes. Large amounts of evidence for this interpretation heavily rely on the presence or absence of costs to the ongoing task. To give a simplified example, take a typical prospective memory intention: remembering to stop by the grocery on the way home from work. If one is monitoring, searching for the right turn to the grocery store and maintaining the intention in mind, they might slow down their driving (i.e., show costs to the ongoing task), because they have fewer attentional resources to devote to the act. However, one could also be driving speedily along without any thoughts about needing groceries, notice the store, and spontaneously retrieve the intention.

The recently proposed delay theory, however, challenges this (fairly) predominant interpretation, and instead proposes that the costs seen to the ongoing task (which has been taken for monitoring) is in fact due to a strategic decision to withhold responding to allow more time for information regarding the prospective memory task to accrue. In the case of spontaneous retrieval, the information accumulation is so quick there is no need to initiate a delay. This theory has support primarily from evidence accumulation models (e.g., Diffusion models) and the work by Heathcote, Loft, and Remington (2015). In our own study, working within the same modeling framework, we created conditions that emphasized delayed responding or monitoring behavior, and compared these to a standard prospective memory condition to determine underlying mechanisms and the modeling behaviors they reflect (Anderson, Rummel, & McDaniel, 2018). Additionally, we have behavioral evidence from manipulating ongoing and prospective memory task accessibility that better supports the multiprocess theory than delay theory (Anderson & McDaniel, under review). See Francis Anderson’s page for references to these studies.

Hey buddy, why don’t we take it outside…the laboratory

Most prospective memory researchers introspectively assume that the topic is an important one, and that we spend a great deal of time and mental effort planning and remembering to execute intentions. We say that very thing in the Brief Introduction; however, other than a few studies like Crovitz and Daniel’s (1984), there isn’t a lot of research explicitly showing this. One such study used experience sampling methods to determine how much of our mental lives was devoted to thinking about the future (Gardner & Ascoli, 2015). They found that a considerable amount of time was spent thinking about the future, but their focus did not explicitly focus on prospective memory. Our own research takes a different methodological stance, but attempts to tackle some of the same basic questions. Most importantly, during a typical day, how much time do we devote towards prospective planning and remembering? Thoughts about the future (30%) were much more frequent than thoughts about the past (13%), though present-focused thinking was the most prevalent (55%). Of all thoughts, approximately 15% were directly related to planning and completing intentions. Further studies will attempt to use this methodology to better understand whether the prospective memory construct operates in the real world as it does in the laboratory.

For more information and updates on current studies, contact Francis Anderson at anderson.f@wustl.edu

First image: http://www.assignmentpoint.com/science/psychology/prospective-memory.html

Second image: https://paton.io/enough-with-the-post-it-notes-7eeb6cce0c07