1. Athey, C., Humour in Children Related to Piaget's Theory of Intellectual Development. Unpublished Master of Education Thesis, University of Leicester (1970).
2. Thinking;Bartlett,1958
3. The Identity of Man;Bronowski,1967
4. Displeasure and pleasure in relation to activity;Buhler,1928
5. The role of surprise in cognitive development;Charlsworth;Studies in Cognitive Development,1969