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I do cryptic crosswords. On my first attempt, I usually finish about half the clues and get stuck. When I return to the crossword the following day, even if I haven鈥檛 been consciously thinking about it, I usually get a few more clues very quickly. But after half an hour at most, I become stuck again. What鈥檚 going on?

Melanie Green, Hemel Hempstead, Hertfordshire, UK

We pay 拢25 for every answer published in New Scientist. To answer this question 鈥� or ask a new one 鈥� visit newscientist.com/lastword. Terms and conditions apply.

This article appeared in print under the headline 鈥淕ive us a clue鈥�