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Parents need to be able to make evidence-based decisions with respect to their children. Whether this be in relation to music exposure or immunization, there is a need for reliable evidence. At a conference of child language researchers I recently attended, Elizabeth Kirk talked about the evidence for baby sign.
Baby sign has made numerous claims about its beneficial impacts on child development, including increases in IQ, reduced stress, better parent-child relationships, and earlier language acquisition. Unfortunately, this has been based on remarkably little evidence. A recent investigation found that claims on more than 33 websites were largely based on opinion pieces, not controlled research.
Opinions are easy to find on almost any topic (like where to put commas), and in favor of whatever viewpoint you may have. They have motivated good and bad education policies and religious wars alike.
What you want to know is what's the evidence...and how much does it weigh?
Experimental research on baby sign is difficult to find. The available studies are often difficult to reproduce.
This is where meta-analyses come into play. Meta-analyses are studies of studies, collecting together bodies of research and asking what is the weight of the evidence.
Science in practice is a bit like a committee--lots of speculative ideas with many, many motivations. If you really want to know what the committee believes, read the meta-analysis.
Several meta-analyses have now sifted through the research. These articles have basically found very little, if any, compelling evidence that baby sign helps normally developing children in any of the ways claimed above.
Why would it, really? Babies learn A LOT of stuff, much of it self-guided. I'm not sure what the mechanism would be for mommy forcing a child's hand into a strange shape turning them into a genius.
I think it's reasonable to point out that the children do learn to sign (a few words), which may help them to communicate. So it is not that baby sign doesn't teach kids to sign. Moreover, if interacting with your child is an alternative to keeping them in a closet, then you should baby sign.
Still, beware the Jabberwock. To claim that aspirin will solve marital problems when all it really does is cure headaches is overselling aspirin and ethically questionable. One might even ask themselves if they want to be involved with a product that uses marketing strategies historically associated with snake oil. I have a little snake oil in my cabinet, and it works fine for me. So I can understand if you are on the fence.
Let's lastly consider one of the biggest relationships researchers have come across so far in relation to baby sign: Maternal anxiety. One might reasonably ask if maternal anxiety goes down for mothers involved in teaching their kids baby sign. The evidence suggests it does not--it may even go up. Baby signers had higher anxiety than the non-signers.
It is generally true that people with higher aspirations are often less satisfied with their outcomes. This is true even when they do better than happier people with lower aspirations. Nor were the parents in this study randomly assigned. It may very well be that stressed or easily stressed people like to pile on stressors. I'm not sure if there is anything you can do about that except watch where you step.
I invite you to read the research yourself and come to your own conclusions.
Howard, L. E., & Doherty-Sneddon, G. (2014). How HANDy are baby signs? A commentary on a systematic review of the impact of gestural communication on typically developing, hearing infants under the age of 36 months. First Language, 34(6), 510-515.
Howlett, N., Kirk, E., & Pine, K. J. (2011). Does ‘wanting the best’create more stress? The link between baby sign classes and maternal anxiety. Infant and Child Development, 20(4), 437-445.
