Why reminders work at first and then fade

Remembering to do something at a certain time, without being prompted, is called time-based prospective memory. Studies of adults and of children with ADHD have found a difficulty here ^{1 2}. Reminders are the obvious fix, and in experiments they work very well. The trouble is what happens over the following weeks.

What the evidence says

The difficulty is specific. In a computerised task with 25 adults with ADHD and 25 without, those with ADHD did as well as others when a cue in front of them triggered the task, and much worse when they had to act at a particular time ¹. A systematic review of research in children found the same split ². In a separate study of adults with ADHD on a more complex task, the difficulty showed up mostly at the planning stage, not in carrying the plan out ³.

Reminders help. In one experiment, forgetting fell from about 45% with memory alone to about 5% with an external reminder ⁴. In a survey study of 112 people’s real-life plans, setting a reminder predicted following through ⁵. In an experiment with a texting task due days later, explicit reminders did better than implicit ones ⁶.

Then the effect wears off. In a six-week study of 44 adults, the effect of walking prompts was large at first and shrank over time ⁷. In a brain-imaging study of computer security warnings, seeing the same warning again and again reduced the brain’s response to it ⁸.

Volume makes it worse. In one study, 15 smartphone users received an average of 63.5 notifications a day, and more notifications were associated with worse mood ⁹. Across about 790,000 notifications from 278 people, only 15 to 25% of non-message notifications led to opening the app ¹⁰. Even useful notifications were dismissed more often when they felt like an interruption ¹¹, and in an experiment a phone notification alone lowered performance on a demanding task ¹².

What we don’t know

Almost none of this was tested in adults with ADHD. In the one ADHD trial we found, weekly text reminders may have led people to log in to a programme sooner, but did not increase how many modules they finished or how often they used the strategies ¹³. Getting someone to look is not the same as getting the thing done.

Things to try

• Keep fewer reminders. If most alerts are ones you ignore, the one that matters gets ignored with them.
• Make the reminder say what to do. Explicit reminders did better than hints ⁶.
• Change what it looks or sounds like from time to time, so it does not fade into the background ⁸.
• Prefer a choice to a command. In an online experiment on messages encouraging people to eat more vegetables, offering a choice improved how people rated the programme, while softer wording made no measurable difference ¹⁴.
• Make the plan visible without an alert, on a wall, a lock screen or a widget. This follows from the finding that cue-triggered remembering holds up better than time-triggered remembering ¹. It has not been tested directly.