According to Steinar Brandslet
Of the 12 children who participated in the course that the researchers studied, 11 managed to stand on their own for more than 15 seconds by the end of the sessions. The 12th baby also managed to stand for a good 8 seconds. Instructor Snorri says this is a common experience.
“On average, the children were 4.3 months old when they learned to stand without support. The youngest was only 3.6 months old,” says Sigmundsson. He points out that once the babies learn to stand, they don’t forget how.