We need to talk about validity - A commentary on "Six solutions for more reliable infant research" from the viewpoint of an early executive functions researcher.

Considering measurement reliability and effect sizes is important for robust infant research and for optimising infant tasks to measure group-level effects or individual differences.Construct validity - making sure that we measure what we think we are measuring - is also important.A robust effect at the group-level may not always restrict reliability - it depends on the amount of true variation between infants.