Prospective memory (PM) refers to an ability to remember carrying out previously formed intentions in the future. The demand for performing PM tasks in everyday increases as children enter schools. The key cognitive processing to complete PM tasks successfully involves voluntary retrieval and execution of PM intentions when PM cues occur. There are three types of PM cues, namely time-based (e.g., attend a friend’s birthday party at 7 o’clock on Saturday evening), event-based (e.g., buy fruit when passing a grocery shop), and activity-based (e.g., ask parents to sign on homework when it is completed). The three types of PM cues vary in difficulty of retrieval and may be associated with different demands for attentional resources. Compared with typically developing children, children with Attention Deficit Hyperactivity Disorder (ADHD) are more forgetful and show inattention in daily activities, suggesting potential impairment in PM function. However, few studies have investigated PM in children with ADHD. Moreover, no study has directly compared performance in three types of PM cue conditions and characteristics of the cognitive processing.
In order to address this issue, Dr. Raymond Chan’s team from the Neuropsychology and Applied Cognitive Neuroscience (NACN) Laboratory, CAS Key Laboratory of Mental Health, Institute of Psychology, and his collaborators including Dr Ying Qian from Peking University Sixth Hospital, and Professor Yan-yu Wang from Weifang Medical University have investigated time-, event-, and activity-based PM in 28 children with ADHD and 28 typically developing children using the Fishing game. The Fishing Game adopts the classical dual-task paradigm, and the primary/ongoing task requires children to fish. At the same time, they need to pay attention to PM cues while fishing, and stop fishing to execute PM tasks when the PM cues appear. In the time-based PM cue condition, children need to feed the cat with fish every full minute. In the event-based PM cue condition, children need to feed the cat when they catch a special stripy fish. In the activity-based PM cue condition, children need to row a boat ashore when the game is over and when they observe a big fish bone. In this study, we also measured children’s intelligence and two types of attention functions (i.e., sustained attention and switch attention).
The findings showed that despite lower IQ and attentional deficits, children with ADHD exhibited similar level of PM performance as typically developing children, suggesting no signs of impairment in PM. Subsequent analysis indicated that type of PM cues had a significant impact on PM performance, and the patterns were similar in children with ADHD and typically developing children. Specifically, children in both groups showed the best performances in the activity-based PM task, followed by the event-based PM task, and the time-based PM task. This finding suggests that the ending of an activity as PM cues has certain advantages; children have more attentional resources for PM cues when an activity ends, and thus they are more likely to detect cues and retrieve intentions. However, both event- and time-based cues may need voluntary monitoring during the process of ongoing task. Since temporal cues are often more difficult to detect, they tend to demand higher level of monitoring, leading to worse performance.
It is worth noting that in the event-based PM condition, despite similar performance in PM task, children with ADHD exhibited worse ongoing task performance compared with typically developing children. This may reflect limited attentional resources in children with ADHD. When children with ADHD spend more attentional resources monitoring PM cues and completing PM tasks, they tend to pay larger cost on ongoing task performance compared with typically developing children.
Taken together, these findings suggest that children with ADHD have limited attention and experience difficulty in attending to both PM and ongoing task. Because children with ADHD showed best performance in activity-based PM cue conditions, parents and teachers may try to arrange PM tasks at the end of activities when they assign PM tasks. Under such circumstances, the ongoing task is over and children do not need to pay attention to it and are thus more likely to retrieve the PM intentions. Similarly, as children have difficulty completing time-based PM tasks, parents and teachers should consider replace temporal cues with event- or activity-based cues.
The study has been published online:
Yang, T.-X., Wang, Y.-Y., Wang, Y., Qian, Y., Cheung, E. F. C., & Chan, R. C. K.* (2019). Event-, Time- and Activity-Based Prospective Memory in Children with ADHD. Developmental Neuropsychology, 1-12. doi: 10.1080/87565641.2019.1695801
Yang, T., Chan, R. C. K.*, & Shum, D. (2011). The development of prospective memory in typically developing children. Neuropsychology, 25(3), 342–352. doi: 10.1037/a0022239