Who benefits most? Exploring age effects of episodic future thinking and enactment encoding on prospective memory from childhood to middle adulthood.

Failures to realise delayed intentions (prospective memory, PM) are common in everyday life, yet little is known about how PM performance can be improved. Deeper encoding during intention formation has been proposed to strengthen memory representations and facilitate later retrieval; however, no study has systematically compared different encoding strategies from childhood to middle adulthood. To address this gap, we examined the effects of two encoding strategies - episodic future thinking (EFT; mental practice) and enactment encoding (EE; physical practice) - on PM performance across four age groups. A total of 373 participants were tested, including children (n = 90), adolescents (n = 96), young adults (n = 97), and middle-aged adults (n = 90). Participants were randomly assigned to an EFT, EE, or standard encoding condition and completed a novel computerised PM task. A significant main effect of encoding condition emerged. Overall, participants in the EE condition outperformed those in both the EFT and standard encoding conditions, with no evidence that this benefit differed by age group. Contrary to expectations, EFT did not improve PM performance relative to standard encoding. This unexpected finding is discussed in terms of cue focality and high ongoing task demands.