Most "engagement" features are cosmetic. A product adds points, badges and streaks, sees a short-term lift, and a few weeks later retention is worse than before. That isn't bad luck. It's what motivation research predicts.
The spike, then the drop
Extrinsic rewards work in the short term: people will do more of almost anything to earn points. But when the reward is attached to something they'd have done anyway, it changes why they do it. The activity becomes about the reward. When the novelty of the reward wears off, the original reason has been crowded out, and people leave faster than if you'd done nothing.
Psychologists call this the overjustification effect. You can see its shape in the model below: switch on "points on everything" and watch the curve spike early, then fall below where it started.
People choose how they use it
People feel themselves getting better
How this is calculated
m = (0.35·autonomy + 0.40·competence + 0.25·relatedness) / 100
τ = 4 + 26·m days · floor = 0.04 + 0.30·m
retention(t) = floor + (1 − floor)·e^(−t/τ)
points on everything: early boost ×(1 + 0.25·e^(−t/4)), then τ ×0.6 and floor ×0.5 (the overjustification effect)
A teaching model based on self-determination theory, not a forecast. Real products need real measurement.
What people actually need
Self-determination theory identifies three needs that sustain motivation over time:
- Autonomy: people choose how they use the product, rather than being herded
- Competence: people can see themselves getting better at something that matters to them
- Relatedness: people feel connected to others through what they do
Products that support these needs keep people because they want to stay. Products that ignore them have to keep paying people with rewards, and eventually can't.
What to design instead
Start from one behaviour you want to change, not "engagement" in general. Then ask which need is missing:
- If people don't know what to do next, give them clear goals with real choice about how to reach them.
- If people can't see their progress, make growing skill visible, and tie progression to competence rather than time spent.
- If people feel alone, add social features only where connection genuinely helps.
Rewards still have a place, sparingly and as acknowledgement rather than payment.
No dark patterns
Streak anxiety, guilt-trip notifications and fake scarcity do move numbers for a while. They also erode trust, and trust is what retention runs on. We don't build them.