Prospective Memory

I've written at length about implementation plans in my book “Planning to Remember: How to Remember What You're Doing and What You Plan to Do”. Essentially, they're intentions you make in which you explicitly tie together your intended action with a specific situational cue (such as seeing a post box).

A new study looked at the benefits of using an implementation intention for those with low working memory capacity.

The study involved 100 college students, of whom half were instructed to form an implementation intention in the event-based prospective memory task. The task was in the context of a lexical decision task in which the student had to press a different key depending on whether a word or a pseudo-word was presented, and to press the spacebar when a waiting message appeared between each trial. However (and this is the prospective element), if they saw one of four cue words, they were to stop doing the lexical task and say aloud both the cue word and its associated target word. They were then given the four word pairs to learn.

After they had mastered the word pairs, students in the implementation intention group were also given various sentences to say aloud, of the form: “When I see the word _______ (hotel, eraser, thread, credit) while making a word decision, I will stop doing the lexical decision task and call out _____-______ (hotel-glass, eraser-pencil, thread-book, credit-card) to the experimenter during the waiting message.” They said each sentence (relating to each word pair) twice.

Both groups were given a 5-minute survey to fill out before beginning the trials. At the end of the trials, their working memory was assessed using both the Operation Span task and the Reading Span task.

Overall, as expected, the implementation intention group performed significantly better on the prospective memory task. Unlike other research, there was no significant effect of working memory capacity on prospective memory performance. But this is because other studies haven't used implementation intentions — among those who made no such implement plans, low working memory capacity did indeed negatively affect prospective memory performance. However, those with low working memory capacity did just as well as those with high WMC when they formed implementation intentions (in fact, they did slightly better).

The most probable benefit of the strategy is that it heightened sensitivity to the event cues, something which is of particular value to those with low working memory capacity, who by definition have poorer attentional control.

It should be noted that this was an attentionally demanding task — there is some evidence that working memory ability only relates to prospective memory ability when the prospective memory task requires a high amount of attentional demand. But what constitutes “attentionally demanding” varies depending on the individual.

Perhaps this bears on evidence suggesting that a U-shaped function might apply, with a certain level of cognitive ability needed to benefit from implementation intentions, while those above a certain level find them unnecessary. But again, this depends on how attentionally demanding the task is. We can all benefit from forming implementation intentions in very challenging situations. It should also be remembered that WMC is affected not only more permanently by age, but also more temporarily by stress, anxiety, and distraction.

Of course, this experiment framed the situation in a very short-term way, with the intentions only needing to be remembered for about 15 minutes. A more naturalistic study is needed to confirm the results.

Older news items (pre-2010) brought over from the old website

Why it’s so hard to disrupt your routine

New research has added to our understanding of why we find it so hard to break a routine or overcome bad habits. The problem lies in the competition between the striatum and the hippocampus. The striatum is involved with habits and routines, for example, it records cues or landmarks that lead to a familiar destination. It’s the striatum that enables you to drive familiar routes without much conscious awareness. If you’re travelling an unfamiliar route however, you need the hippocampus, which is much ‘smarter’.  The mouse study found that when the striatum was disrupted, the mice had trouble navigating using landmarks, but they were actually better at spatial learning. When the hippocampus was disrupted, the converse was true. This may help us understand, and treat, certain mental illnesses in which patients have destructive, habit-like patterns of behavior or thought. Obsessive-compulsive disorder, Tourette syndrome, and drug addiction all involve abnormal function of the striatum. Cognitive-behavioral therapy may be thought of as trying to learn to use one of these systems to overcome and, ultimately, to re-train the other.

[931] Lee AS, Duman RS, Pittenger C. A double dissociation revealing bidirectional competition between striatum and hippocampus during learning. Proceedings of the National Academy of Sciences [Internet]. 2008 ;105(44):17163 - 17168. Available from:

Brain's voluntary chain-of-command ruled by not 1 but 2 captains

Previous research has shown a large number of brain regions (39) that are consistently active when people prepare for a mental task. It’s been assumed that all these regions work together under the command of one single region. A new study, however, indicates that there are actually two independent networks operating. The cingulo-opercular network (including the dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex) is linked to a "sustain" signal — it turns on at the beginning, hums away constantly during the task, then turns off at the end. In contrast, the frontoparietal network (including the dorsolateral prefrontal cortex and intraparietal sulcus) is active at the start of mental tasks and during the correction of errors. The findings may help efforts to understand the effects of brain injury and develop new strategies to treat such injuries.
Dosenbach, N.U.F. et al. 2007. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, 104 (26), 11073-11078.

Planning is goal-, not action-, oriented

Studies in which monkeys were asked to perform a complex task involving several discrete steps have revealed that the brain's "executive" center, in the lateral prefrontal cortex, plans behaviors not by specifying movements required for given actions, but rather the events that will result from those actions.

Mushiake, H. et al. 2006. Activity in the Lateral Prefrontal Cortex Reflects Multiple Steps of Future Events in Action Plans. Neuron, 50, 631–641.

Time really does fly when you’re busy

We all know that time goes faster when we’re busy, but though scientists have long tried to prove a link between attention and time estimation, it has been difficult to design an experimental manipulation that only manipulates attention and not other, potentially confounding variables. But now, it seems, two researchers have managed to do it – and the finding is clear. Results showed that an attentionally demanding search task produced a large underestimation of time, and that as the amount of attention increased, so did the underestimation of time. Note that the study involved prospective estimates of time (participants knew in advance that they would be asked how long the task took), rather than retrospective.

Chaston, A. & Kingstone, A. 2004. Time estimation: The effect of cortically mediated attention. Brain and Cognition, 55 (2), 286-289.

More light shed on how episodic memories are formed

A rat study has revealed more about the workings of the hippocampus. Previous studies have identified “place cells” in the hippocampus – neurons which become more active in response to a particular spatial location. Activity in the hippocampus while rats searched for food in a maze where the starting and ending point was varied, has found that, while some cells signaled location alone, others were also sensitive to recent or impending events – i.e., activation depended upon where the rat had just been or where it intended to go. This finding helps us understand how episodic memories are formed – how, for example, a spatial location can trigger a reminder of an intended action at a particular time, but not others.

Suzuki, W. A. (2003). Episodic Memory Signals in the Rat Hippocampus. Neuron, 40(6), 1055–1056. doi:10.1016/S0896-6273(03)00806-7

Imaging confirms role of frontal lobes in planning

New research provides the first neuro-imaging evidence that the brain's frontal lobes play a critical role in planning and choosing actions.

Connolly, J.D., Goodale, M.A., Menon R.S. & Munoz, D.P. 2002. Human fMRI evidence for the neural correlates of preparatory set.Nature Neuroscience, 5 (12),1345–1352.

Role of prefrontal cortical regions in goal-directed behavior

Goal-directed behaviour depends on keeping relevant information in mind (working memory) and irrelevant information out of mind (behavioural inhibition or interference resolution). Prefrontal cortex is essential for both working memory and for interference resolution, but it is unknown whether these two mental abilities are mediated by common or distinct prefrontal regions. An imaging study found there was a high degree of overlap between the regions activated by load and interference, while no region was activated exclusively by interference. The findings suggest that, within the circuitry engaged by this task, some regions are more critically involved in the resolution of interference whereas others are more involved in the resolution of an increase in load.

Bunge, S.A., Ochsner, K.N., Desmond, J.E., Glover, G.H. & Gabrieli J.D.E. (2001). Prefrontal regions involved in keeping information in and out of mind. Brain, 124 (10), 2074-2086.