Toddlers show leg preference early on, say researchers
University of Haifa study shows evidence even during crawling
Which leg a toddler prefers to use, which reflects dominance of one brain hemisphere over the other, was thought to become clear relatively late. In the past, it was assumed that babies’ brains are symmetrical in structure and function until the age of two years, while functional asymmetries develop at a later stage.
Thus leg preference was studied by researchers only from three years and above.
However, University of Haifa researchers have for the first time documented evidence of the development of leg preference in babies during the crawling and “pulling to stand” (PTS) stage as part of the normal developmental process.
The study was published in the online journal Laterality: Assymetries of Body, Brain and Cognition.
Physiotherapy researcher Dr. Osnat Atun-Einy said: “This is the first study to examine leg preference in the context of pulling-to-stand and crawling in an asymmetrical pattern.
Expanding our knowledge about leg preference and identifying the lead leg during PTS forms an important frame of reference of understanding typical motor performance in babies.”
She noted that the main significance of these findings is that functional asymmetry, with a division of functions between a stabilizing side and a leading side in lower limb functions, is a reflection of anatomical and brain asymmetry.
Therefore, she urged that neither parents nor doctors make an effort to influence or intervene in this preference.
“Clinicians who are unaware of the existence of this phenomenon among the population with typical development may direct their interventions to increase symmetry in leg function.
“A better understanding of this process in the normal population will enable us to develop clinical applications for populations with atypical development, and to distinguish between leg preference and abnormal asymmetry,” Atun-Einy stressed.
Babies with typical development show asymmetrical behavior in their lower limb activity during the PTS stage.
“From a developmental perspective, it is very important to examine and understand the typical normative range of motor development in order to identify individual differences or atypical behavior,” said Atun-Einy, who undertook the study under the supervision of Prof. Anat Scher of the university’s education and human development department.
The phenomenon of side preference has fascinated many researchers from different fields as one of the prominent manifestations of brain side dominance.
In their study, the researchers focused on the stage when babies begin to stand up – with support – from a half-kneeling or asymmetric four-point kneeling. The study included 27 healthy babies with normal development aged from seven to 12 months.
Seventy-eight percent of the babies showed a clear leg preference when standing from a half-crawl position or from asymmetric four-point kneeling.
Moreover, a group of babies was identified that preferred to use the same lead leg in all PTS movements within a few months of acquiring PTS capabilities.
The researcher noted that the preferred leg at this stage may not necessarily be the dominant leg at a later stage.