The movement behaviors of typically developing infant are characterized by many repetitions of actions as they explore different options for achieving a goal.

These repetitions vary from across time, with each repetition providing different sensory-motor linkages and error messages which allow for adaptation of the motor plan for subsequent actions.

Over time and with practice the infant will select  a few strategies which are most efficient, and reduce the use of the non-preferred strategies (reduce variability).

Variability is seen in the infant's earliest repetitive spontaneous movements, such as kicking and early reaching. 

A lack of movement variability is frequently identified in infants and children who have developmental delays or disabilities. Kyvelidou 2010

The general movement assessment is a widely used assessment of movement variability, also termed ‘variations’ by some researchers, in young infants.[20, 22]

Kyvelidou, A., Harbourne, R. T., & Stergiou, N. (2010). Severity and Characteristics of Developmental Delay Can Be Assessed Using Variability Measures of Sitting Posture. Pediatric Physical Therapy : The Official Publication of the Section on Pediatrics of the American Physical Therapy Association, 22(3), 259–266. http://doi.org/10.1097/PEP.0b013e3181ea75f1