Is your baby twitching in her sleep? Don't panic. Resist the urge to pick her up, to hold her limbs down, or to play whackahand. Contrary to what you may think, the baby isn't beginning to wake up, or flailing in her dreams. Recent research suggests that she might actually be learning what arms and legs do, and figuring out how to use them together.
This is not a new idea. 40 years ago, a paper in Science first investigated the prime purpose of "dreaming sleep" in newborn human babies. The authors, scientists from the New York State Psychiatric Institute, found that a baby spends about one third of its existence in rapid eye movement (REM) sleep with continuous muscle contractions (that is, twitching). The high levels of brain activity recorded during this time led them to propose that the purpose of these jerky movements is development.
The idea gained traction in the early 2000s, when Swedish scientists studied newborn rats and showed that spontaneous muscle twitches can help improve the spinal cord's vital withdrawal reflex (the one that kicks in when we accidentally touch fire). A decade later, roboticists at the Swiss Federal Institute of Technology Zurich took a computer simulation of a developing system of muscles and nerves, and fed it random contractions. The circuitry that developed turned out to look astonishingly like the reflex circuitry in mammals. Which suggests the twitches might not just be improving our reflexes, but actually be creating the reflex system in the first place.
In a recent review in Current Biology, University of Iowa professor Mark Blumberg gives us more reasons to believe that twitching is vital to development. His team used high speed video to monitor newborn rats, and found surprising patterns in their seemingly chaotic limb movements. If, say, a pup brought one of its shoulders towards its body, then it was highly likely to flex the elbow of the same limb next. These coupled movements suggest that they are learning increasingly choreographed motions, possibly developing coordination for the complex movements required for adult life.
So the next time your baby starts to flail his little arms or beckons you in his sleep don't wake him up. You might be interrupting a vital learning process!