As well as being looked after by their parents most children experience some form of child care. Research into the effects of child care has produced mixed results but this could be because it has not taken into account children's temperaments*. Researchers at Birkbeck University in London studied 968 families at ten different locations across the U.S. They found that the effects of the quantity and type of child care were similar for all children. However, the effects of quality of child care were much more pronounced in children with a 'difficult' temperament. Low-quality child care led to more behaviour problems in these children than in children with an 'easy' temperament. High-quality child care though led to the children with 'difficult' temperaments having fewer behaviour problems than those with 'easy' temperaments.
Pluess, Michael and Belsky, Jay - Differential susceptibility to rearing experience: the case of childcare Journal of Child Psychology and Psychiatry April 2009, 50(4), 396-404
*For an explanation of the psychological concept of temperament see