What is the Role of Repetitive Behavior in Child Development?

We’ve all seen babies wiggle and wave their arms and legs in the air. Infants engage in various repetitive, stereotyped behaviors such as kicking, waving, or rocking. What are stereotyped behaviors?  They are repetitive actions that are fixed in form and orientation[1]. The motions are simple: either flexion and extension of a basic muscle group or simple rotation around an axis. The motivation for these behaviors appears to be internal, not driven by an external stimulus. Instead, they are conducted for the sake of the movement itself. Parents encourage these movements by providing toys for banging, arm waving, and bouncing.

A study of the types of stereotypical behaviors in neurotypical infants from one month old to a year showed that all babies performed these behaviors[2]. The babies progressed through certain behaviors over time that was highly correlated with particular stages of neuromuscular maturation. Rhythmic leg kicking, for example,  preceded repetitive actions of the arms or legs. Hand and knee rocking preceded crawling. Finger flexing occurred just before an infant acquires the ability to grasp various objects.

The amount of repetitive behavior that an infant engages in depends on whether or not they are being moved in some way by a caregiver[3]. Infants that are rocked, bounced, or carried by a parent show significantly less stereotyped behavior than infants left alone in a car seat, high chair, or playpen. In scientific terms, stereotypy is inversely related to the amount of vestibular stimulation. Vestibular stimulation is stimulation of the hair cells in your inner ear that help you detect and adjust your own motion and balance.

Why do infants do this? Learning how to move takes practice! Scientists have theorized that repetitive behavior helps infants practice their motor skills, helping to make movement more coordinated, refined, and directed[4]. Whether this practice is essential for the brain, the nerve-muscle junction, or at the level of feedback between the sensory and motor system is unknown.

Older neurotypical children from the age of 2-4 exhibit other stereotyped behaviors, called ritualized behaviors. Ritualized behaviors occur most often at bedtime, mealtime, and baths, or when a transition is accompanied by normal fears or anxieties.[5] These include Insistence on Sameness (same story, same video, same clothes) and an obsession with things being Just Right (i.e., the cookie must be whole, not broken; toys must be arranged in particular patterns; clothing preference is based on how clothes feel)[6].  These types of behaviors also show a developmental pattern, with the onset of Insistence on Sameness occurring on average from 14 to 19 moths, while the onset for insistence on objects being Just Right occurring later, at 21 to 26 months[7]. The incidence of ritualized behaviors peaks at 2 to 4 years, with two out of three neurotypical children exhibiting these behaviors. The behaviors then decline in frequency, as the child matures emotionally and socially.

Why do toddlers do this? What is the developmental purpose of ritualized behaviors? Some have hypothesized that they are a way to help a child organize, accommodate, and eventually master the environment. Others propose that it helps children gain a sense of self-control and helps them regulate their internal emotional state[8].



References

[1]  Dantzer R (1986) “Behavioral, physiological and functional aspects of stereotyped behavior: A review and a re-interpretation.  J Anim Sci 62: 1776-1786.

[2]  Thelen E (1979)  “Rhythmical stereotypies in normal human infants.” Anim Behav 27: 699-715.

[3]  Thelen E (1980)  “Determinants of amounts of stereotyped behavior in normal human infants.” Ethol Sociobiol 1: 141-150.

[4] Symons FJ, Sperry LA, Dropik PL, Bodfish JW (2005). “The early development of stereotype and self-injury: a review of research methods.” J of Intellectual Disability Research 49@0): 144-158.

[5] Evans DW, Leckman JF, Carter A, Jeznick JS, Henshaw D, King RA, Pauls D (1997). “Ritual, habit, and perfectionism: The prevalence and development of compulsive-like behavior in normal young children.” Child Dev 68(10: 58-68.

[5] Ibid.

[6] Ibid.

[7] Ibid.

[8] Evans DW, Leckman JF, Carter A, Jeznick JS, Henshaw D, King RA, Pauls D (1997). “Ritual, habit, and perfectionism: The prevalence and development of compulsive-like behavior in normal young children.” Child Dev 68(10: 58-68.










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