An experimental group is the group in an experiment that receives the variable being tested. One variable is tested at a time. The experimental group is compared to a control group, which does not receive the test variable. In this way, experimental groups are used to find answers in an experiment.
1 At around 9 months of age, babies begin to pull themselves up to a standing position. 2  By 10 months of age, a baby should be able to grasp objects with thumb and forefinger.
What age do babies first give a social smile Babies or infants usually start smiling for a purpose when they are six to eight weeks old as their muscles around the face begin to strengthen [6]. During this time, the babiesâ capacity to maintain an eye contact stabilizes with their brain gradually starting to develop.