Now, what were we talking about? Effects of topic reminders on discourse coherence in young and older adults

Objectives: Coherent speech remains focused on the topic at hand, avoiding irrelevant or tangential comments. Discourse coherence often declines with age and this has been linked to declines in cognitive control processes that regulate activation of knowledge and ideas. The present study tested whether external topic reminders could improve coherence by reducing reliance on internal control processes. Methods: 77 young and older adults produced spoken discourse in response to topic prompts. In the baseline condition, the topic prompt was removed when the participant began speaking. This was compared with conditions where a reminder was presented on screen, either throughout their response or only during the last 30 seconds. Results: Both age groups produced more coherent, topic-focused responses when they had access to a topic reminder. Late reminders had an additional proactive impact on participants’ speech, increasing its coherence even before the reminder appeared. This proactive effect was short-lived in the older group but more sustained in the young group. Discussion: When speaking, people must maintain the current discourse goal (i.e., intended topic), in order to prioritise relevant information and inhibit irrelevant ideas. Topic reminders boost activation of the discourse goal, reducing the need to maintain this through internal control. Furthermore, people proactively strengthened goal activation when they anticipated a later reminder, but older people were less effective at maintaining this throughout their response. Together, these results suggest that internal maintenance of discourse goals is less effective in older people, though they do benefit from external cues that support topic maintenance.