Rewards undermine kids’ intrinsic interest in an activity by convincing them that they are doing it for the reward and not becase the task is enjoyable in itself. Better to offer incentives strong enough to get children to perform the desired activity, but not so strong that they see the rewards as the only reason for doing it. Non-salient rewards are better ie prize offered, but not hyped up or displayed. Overjustification effect and minimal sufficiency (Mark Lepper) principle: start with rewards strong enough to entice initial participation but then dilute over time.
Helping kids internalize desired values involves helping them label their feelings. eg label kids as non-litterers rather than just making it a rule. Or point out how unpleasant it is to feel guilt, cf driving child to be more sneaky.
Labels matter – if they imply a fixed mindset or ability, eg you’re good at maths, then it can be a shock when things start to slide. Better to highlight growth, praise for effort, link effort to results.