Dr Gareth Moore (B.Sc (Hons) M.Phil Ph.D) is the internationally bestselling author of a wide range of brain-training and puzzle books for both children and adults, including Anti-stress Puzzles, Ultimate Dot to Dot, Brain Games for Clever Kids, Lateral Logic, Extreme Mazes and The Ordinance Survey Puzzle Book. His books have sold over a million copies in the UK alone and have been published in 29 different languages. Helena Gellersen is doctoral candidate in psychology at the Memory Laboratory for the University of Cambridge. Her background is in cognitive psychology and neuroscience and she is involved in scientific behavioural research on learning and memory, focusing on individual differences in memory abilities, with a particular emphasis on healthy ageing and early signs of cognitive decline. She has had a number of papers published and in her spare time she volunteers for a student-run think tank on global health.