Discussion

For the first time, the present study explored age differences in prospective memory performance across the pre-school age-range in an age-standardized task procedure that explicitly equates ongoing task difficulty as suggested by Kvavilashvili et al. (2008).

Moreover, the effect of motivation on pre-schoolers’ prospective memory performance under laboratory control and given equal ongoing task difficulty was tested. The findings have several conceptual and methodological implications.

A first important finding was that indeed ongoing task performance was comparable across both age groups. This is in contrast to previous studies on prospective memory

performance in pre-schoolers which either found worse performance in at least main parts of ongoing task performance in the younger group compared to the older group (e.g., Guajardo

& Best, 2000; Kliegel & Jäger, 2007; Wang et al., 2008) or did not report ongoing task performance at all (e.g., Somerville et al., 1983). So far, as indicated by Kvavilashvili et al.

(2008) this pattern had constituted a general caveat to the existing literature on prospective memory performance in pre-schoolers, even though some studies presented initial

circumstantial evidence that performance differences in the ongoing tasks likely had not

caused the obtained age differences in prospective memory. For example, Wang et al. (2008) have argued that the same age effect on prospective memory performance appeared across several ongoing task conditions that placed more or less demands on ongoing task activities, and Kliegel and Jäger (2007) found age differences to remain even after partialling out individual differences in ongoing task performance. While these approaches deal with the problem of differential ongoing task difficulty and performance across age groups, the present study suggests one methodological approach that – at least in the present experiment –

succeeded in a-priori equating ongoing task difficulty. Extending early adult aging studies that have chosen a somewhat similar approach by generally allowing older adults more time or presenting them with less items (e.g., Einstein & McDaniel, 1990), the present approach utilizes the well-standardized and age-scaled diagnostic materials available for children. This allows for much more precise and fine-grained designing of age-appropriate ongoing task material in the study of prospective memory in children (see Zimmermann & Meier, 2006, for an alternative approach).

That comparable ongoing task performance may indeed be an important requirement for studying prospective memory performance in pre-schoolers is suggested by the finding of no general age effect in prospective memory performance in the present study. Across both motivational conditions younger schoolers did not statistically differ from the older pre-schoolers. This is in contrast to at least part of the literature as, e.g., Guajardo and Best (2000) as well as Kliegel and Jäger (2007) have reported reliable age differences for the two age groups studied in the present experiment. A potential explanation for the lack of a main effect of age comes from Kvavilashvili et al. (2001) and Wang et al. (2008). Those studies have demonstrated that task interruption seems to be an important factor influencing prospective memory performance in young children. Examining similar age groups as the present study, Wang et al. (2008) found that prospective memory was only reduced in younger pre-schoolers compared to older ones if the prospective response required active task interruption of the

ongoing task; in contrast, if the prospective response did not require active task interruption there was no age effect. The present study applied a task that did not require active task interruption of the ongoing activity and consistent with these previous two studies did not find a main affect of age. In this context, it has to be noted that although the prospective memory task itself can be considered as relatively low demanding, the children in the present study showed only medium to low performance levels. This might be due to the age-appropriate task material chosen for the ongoing activity phase that was originally constructed and standardized for a test to assess age-appropriate maximum performance levels in general ability. However, as ongoing task difficulty was not systematically varied but explicitly equated in the present study, this as to remain speculative at this point and awaits direct empirical testing.

Regarding the age effect, the present results, hence, largely dovetail with the previous studies on pre-schoolers’ prospective memory performance. However, they do not only replicate Wang et al.’s (2008) no interruption findings. Specifically, the observed age x motivation interaction revealed that – under specific conditions such as low motivation – younger pre-schoolers may indeed show severely reduced prospective memory performance even in a task that equates ongoing task difficulty. Or in other words, only in tasks that are sufficiently motivating may even young pre-schoolers perform as well as older pre-schoolers.

This finding is largely consistent to Somerville et al. (1983), where 2-year-old children performed in the high interest condition as well as 4-year-olds while the performance of the youngest was reduced in the low interest (long delay) condition. From a conceptual

perspective, the results may reflect that especially in younger children, where the cognitive resources required for successful prospective memory performance (such as attention and retrospective memory) are still developing, motivating or important tasks may help allocating the available resources to the task elements of interest.

However, the data also revealed a lack of an overall effect of motivational incentives.

This was mainly due to older pre-schoolers’ performance and could be seen as being in line with Guajardo and Best (2000) who found no significant effects of reinforcements given for accurate performance. However, Guajardo and Best reported this to occur for both age groups. One possible explanation for this inconsistency could be the way of manipulating motivation. Guajardo and Best externally rewarded correct performance in a computer-based task that itself may be seen as rather neutral. In contrast, in the present study, we directly asked the children to remember to execute an action that itself was internally more or less motivating. Alternatively, the presents children could get out of the magic box might have been of differential interest for the two age groups; although post-experimental observations of children and their presents argue against this. Furthermore, the statistical procedure used in the study might also be a factor contributing of missing overall effects of motivation and/or age, since nonparametrical procedures have relatively limited statistical power compared to parametric tests. Yet, due to the coding of the results, no parametric tests could be applied.

Nevertheless, future studies will have to empirically address these alternatives.