Children are famously bad at remembering to do things - for example, taking out the trash. What exactly is the developmental trajectory of the ability to remember and execute planned actions (known as prospective memory)? Although the effects of traumatic brain injury and old age on prospective memory are becoming elucidated, we have little idea how prospective memory comes to function in the first place. This is the topic covered by Kliegel & Jager's 2007 article in Cognitive Development.
Previous had suggested that even 2-year-olds might have some capacity for prospective memory, although only with highly salient and motivating stimuli (i.e., remember to get candy or icecream). Surprisingly, this previous work had showed that there were no developmental trends across the preschool years. A few other studies looking at preschool-aged children revealed developmental increases in PM across this timeframe, but are limited in their generality due to methodological problems (few subjects, failure of children to remember the goal or purpose of the tasks, or lacking control conditions).
To remedy these shortcomings, Kliegel & JÃ¤ger sequentially presented 10 pictures to each of 119 children (aged 2 to 6 years). The children had to name the pictures on each card. One picture out of every ten was a picture of an apple, which children had been instructed to place in a box. The box was placed behind half of the children, but was continuously visible for the other half (and therefore served as a memory aid). In addition, a real apple was placed on the table, as an additional memory aid. This process was repeated three times total, preceeded each time by a short filler task. Prospective memory was measured as the number of times children correctly put the apple card in the box.
As expected, prospective memory was signficantly better among those children who could see the apple & box relative to those who did not have this memory aid, but this had its strongest effect among the 3-year-olds. In contrast, the majority of the youngest group could not successfully recall the task instructions at the conclusion of the experiment, nor did they perform significantly above chance. Although 3-year-olds performed above chance, they were significantly worse than the older age groups on their prospective memory. Interestingly, none of the other age groups differed in prospective memory ability.
On the other hand, this result is somewhat ambiguous. For example, PM could appear not to improve between 3 and 6 because of ceiling effects (and indeed, 4 and 6-year-olds showed close to perfect performance on average). Another possibility is that PM could appear to show no change on this task despite differing in its underlying mechanism between these age groups.
Children, like adults, may have at least two PM strategies that do not necessarily differ in their resulting accuracy. In particular, monitoring strategies are thought to rely on vigilance and sustained attention, reliant on the prefrontal lobes. One might therefore expect that the an ongoing task would be more lengthened by a concurrent prospective memory task, even controlling for PM performance, as children get older. This could be an important direction for future work. Likewise, one might expect simultaneous trends in performance on tasks which rely on monitoring or active search strategies, such as AX-CPT.
Kliegel, M. & JÃ¤ger, T. (2007). The effects of age and cue-action reminders on event-based prospective memory performance in preschoolers. Cognitive Development, 22:1, pp. 1-148 (January-March 2007)