(Please note, this is an updated version of a previously published post...)
Typically, when I look at a list of baby milestones for physical development, it reads something like this-
1 Month- Lifts head
2 Months- Holds head up
3 Months- Does mini push-up
Well, there’s obviously got to be more going on than that. What inside of baby is suddenly clicking to make this stuff happen?
The vast majority of all physical movements in the first three months of life are just reflexes, most with rather obvious evolutionary survival functions. In fact, human infants appear to have the least developed motor capabilities when compared to other vertebrate animals, making reflexes all the more essential. The first reflexes that parents are most likely to observe are the rooting and sucking reflexes, necessary for nourishment. Other reflexes ensure the proximity of the caretaker to the infant- the grasping reflex, the Moro reflex (this happens when baby is startled- he clenches his arms around his chest in an effort to hold on to his caretaker who would be holding him- demonstrating the evolutionary roots of baby-wearing), and even crying.
Around month 3, many of these reflexes start to diminish and are replaced by movements initiated by the infant, indicating increased strength and the ability to manage their muscles. However, these new movements do not only indicate increased strength of the muscle groups employed. The development of the musculoskeletal system is related to the development of the brain. As explained by the Russian psychologist Nikolai Bernstein in 1967, the movements require coordination. His work explained that the human body- composed of countless joints, muscles, and bones- is unable to control the movement of individual joints and muscles, thus the need for coordination between the separate components. Bernstein called this new field of study “biodynamics.” Beyond the many, many body parts involved in a movement, the central nervous system sends countless signals to initiate movement. Moreover, more than one signal can initiate the same movement or the same signal can lead to different movements, which Bernstein termed as redundancy. Given these findings, Bernstein concluded the human body has an infinite number of degrees of freedom, or the movement or rotation of various parts- imagine rotating your arm.
So, how does the human body learn to master these movements, given an infant’s starting point is based solely on reflexes? This question has been coined “Bernstein’s problem.” Various theories explain how humans develop to overcome Bernstein’s problem. In this look into infant physical development, I will explore the following major theories:
1. 1. Maturation (Neural Networks)
2. 2. Information Processing
3. 3. Direct Processing
4. 4. Dynamic Systems Approach
5. 5. Constraints Model
Crain, William. (2011). Theories of development: Concepts and applications. New Jersey: Prentice Hall.
Salkind, Neil. (2004). An introduction to the theories of human development. California: Sage Publications.
Sporns, Olaf & Gerald Edelman. (1993). Solving Bernstein's problem: A proposal for the development of coordinated movement by selection. Child Development. 64(4). 960-981.