Bildnachweise

• Boy shouting
  
  • iStock photo, #3852295, 07-24-07 © David Hernandez

• Boy's room
  
  • iStock photo, #4785881, 11-27-07 © Galina Barskaya

• Baby in yellow shirt playing with blocks looking up surprised
  
  • iStock photo, #11793563, 01-23-10 © Nadezhda Kulagina

• many colour building blocks
  
  • iStock photo, #12632010, 04-14-10 © greg801