Search	Key Word (KW) or Subject Heading (SH)	Terms	Results
#1	KW	Play OR preten* OR game* OR toy OR recreation (all fields)	13,928
#2	SH	Play OR imaginative play OR symbolic play OR games	1925
#3	KW	Train OR trains OR train set OR train track OR train play OR Thomas the tank engine OR Thomas and friends OR Hornby (all fields)	974
#4		1 OR 2	13,928
#5		4 AND 3	62
Note. For key words related to ‘Train’, the term ‘train*’ was not used as it resulted in many irrele-vant articles, largely related to the term ‘training’. Subject headings in the British Education In-dex were different to those used in PsycInfo due to database differences, and an analogous term for ‘railroad trains’ did not exist. Additionally, though there was functionality to set a limit to childhood; this removed many relevant papers and so was not used.