Tethering a foot to a mobile
Three to four months old, a baby lies in a crib. One foot is lightly tethered to a mobile overhead. At first there’s nothing special happening – kicks, pauses, the usual background chatter of an infant body exploring itself. Then, because the string is attached, a kick makes the mobile sway. The mobile swaying makes the baby notice.
Florida Atlantic University researchers set out to watch that notice land. The question is old – when and how do we learn we can change the world around us? – but the way they asked it is new. Instead of filming the baby alone, they filmed the pair: infant plus mobile, in three dimensions, and tracked how the two movements lock together.
Gisele Galoustian reported the work for Neuroscience News on September 18, 2023. The paper is “Meaning from movement and stillness: Signatures of coordination dynamics reveal infant agency” by Nancy Jones et al., published in Proceedings of the National Academy of Sciences. Funding came from the FAU Foundation and NIH’s National Institute of Mental Health MH-080838.
Motion capture finds the flip
The baby-mobile pairing has been used since the late 1960s. Historically researchers watched infant kicking and inferred learning from that side only. This FAU team is the first in about 50 years to measure mobile motion directly and to run a coordinative analysis across infant, mobile and their interaction.
With cutting-edge motion capture they recorded the experiment in 3D. Infants start as disconnected observers. Connect the foot and the mobile moves with every push. The researchers hunted for the moment the child recognizes causal power – the “aha!” that moves behavior from spontaneous to intentional.
J.A. Scott Kelso, Ph.D., senior author and Glenwood and Martha Creech Eminent Scholar in Science at FAU’s Center for Complex Systems and Brain Sciences, frames it as feedback. Movement makes the mobile move, the mobile moving feeds back to the infant, and at some threshold of coordination the baby recognizes the link and kicks more deliberately. That recognition shows up as a sudden jump in movement rate.
Aliza Sloan, Ph.D., lead author and postdoc in the Center for Complex Systems and Brain Sciences, built a detector for those jumps. The idea is to treat the birth of agency as a eureka-like phase transition in a dynamical system that includes baby, brain and environment. The system goes from loosely correlated to tightly coupled: mobile motion and tethered limb start moving together as the infant discovers the functional connection.
Analysis and modeling point to agency emerging from coupling, not from the baby in isolation. It’s the relationship between organism and environment that gives the experience of “I can make this happen.”
Stillness matters as much as kicks
The team expected action to tell the story. Pauses told it too.
Nancy Jones, Ph.D., co-author, professor in FAU’s Department of Psychology and director of the WAVES Lab, said the data made clear that active movements aren’t the whole picture. Motion and stillness both carry information for an infant mapping its place in the world.
A full coordinative analysis of baby motion, mobile motion and their interaction shows emergence of agency as a punctuated self-organizing process where meaning lives in movement and in stillness. Kelso described it as action in the midst of inaction and inaction in the midst of action. Those rhythms, he argued, jointly form a baby’s conscious awareness that it can make things happen, intentionally.
That view comes from Coordination Dynamics, Kelso’s framework for how living systems coordinate, from cells up to societies, and how function arises. Here agency is treated as an emergent property of the functional coupling between organism and environment, not a pre-made mental module switched on at birth.
Babies discover agency on different timelines
Not every infant found the connection at the same pace. The data showed distinct clusters in when and how strongly bursts of activity appeared. Some babies locked in quickly with sharp, frequent kicks; others took longer, with smaller, more tentative bursts.
Those patterns suggest different behavioral phenotypes of agentive discovery. The team notes the method could provide a way to flag infants who might benefit from early support, opening a preventive window that didn’t exist before.
It’s a reminder that variability is normal. The average story is useful, but the timing and shape of discovery differ from baby to baby, and that difference is measurable.
A 50-year-old setup gets new eyes
Why revisit a classic paradigm? Because fundamental questions about purpose haven’t gone away. Where does purpose come from? How do humans make sense of their relation to the world and realize they can effect change? Those puzzles have engaged thinkers from Isaac Newton to Charles Darwin to Erwin Schrödinger and Niels Bohr.
Goal-directed action shows up in the first months of life, so FAU used young infants as a natural window into how spontaneous movement becomes purposeful. The study doesn’t claim newborns have a mature sense of self or use “I” the way adults do. It does show the seeds of agency – a sense that actions change the world – can be detected within weeks of birth when conditions allow exploration.
For parents, the result matches lived experience: babies aren’t blank slates. They’re alert, responsive, already negotiating what happens to them versus what they make happen. For developmental science, it offers a concrete, measurable foothold on a question that has long resisted quantification.
The “aha!” moment is real enough to time, to track, and to study. For the baby in the crib, it probably feels like a small triumph. For science, it’s a clear signal that agency begins as a dance between body and world, with movement and stillness both leading.
