Children in the older style walkers learned to sit and walk at a similar time to the no-walker group, but learned to crawl later, like the group in the newer walkers. So far as learning to sit and walk goes, then, it seems that if a child can see her feet while in the baby-walker, it has no discernable effect. The newer style walkers, which have large trays that prevent infants from seeing their moving feet and grasping objects around them, lead to greater delays in physical and mental development', says RV Burton. Even if there was a developmental problem with children not being able to see their feet, it could be easily solved by fitting a perspex tray. However, for the study's authors, the preferred solution is to ban baby-walkers altogether.
Walkers do seem to have an effect on crawling.
Both my daughters used walkers and neither of them crawled - ever. Other parents I know have similar experiences. If this study had been conducted by a group of people with no axe to grind they would probably have concluded, given their own evidence, that all infants scored within established norms, and if children using walkers were slower to sit up, crawl and walk, they would soon catch up. But because the study's authors wish to support the call for a ban on baby-walkers, they play up the differences between the groups studied to a degree that their research does not merit. The pervasive hatred of baby-walkers means that any crackpot theory now gets a hearing.