Related Experiment Video
Updated: Aug 15, 2026
Quantifying Learning in Young Infants: Tracking Leg Actions During a Discovery-learning Task
Published on: June 1, 2015
Intra-individual stability of rate of gross motor development in full-term infants
J Darrah1, L Redfern, T O Maguire
1Dept of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada.
Insights
Gross motor skills in infants are not stable month-to-month. This finding highlights the need for repeated assessments using tools like the Alberta Infant Motor Scale (AIMS) to accurately identify potential motor delays in early development.
Area of Science:
- Pediatrics
- Developmental Neuroscience
- Motor Development
Background:
- Gross motor development in infants is crucial for overall development.
- The Alberta Infant Motor Scale (AIMS) is a widely used tool for assessing infant motor skills.
- Understanding the stability of motor scores is important for accurate developmental screening.
Purpose of the Study:
- To evaluate the intra-individual stability of gross motor scores in normally developing infants using the Alberta Infant Motor Scale (AIMS).
- To determine if gross motor skill acquisition follows a predictable pattern in early childhood.
Main Methods:
- Monthly home-based assessments of gross motor skills using the AIMS for 47 infants from 2 weeks of age until independent walking.
- Developmental pediatrician assessment at 18 months to classify motor skills as normal, suspicious, or abnormal.
- Analysis included data from 45 infants classified as having normal gross motor skills at 18 months.
Main Results:
- Individual infant percentile ranks on the AIMS varied considerably month-to-month.
- No systematic pattern of change in gross motor scores was observed across infants.
- Mean percentile range over 13 assessments was 66.78 (S.D. 13.47).
- 14 infants (31.1%) scored below the 10th percentile on at least one assessment.
Conclusions:
- Normally developing infants exhibit instability in the rate of gross motor skill emergence.
- This variability has significant implications for infant screening programs.
- Serial assessments are supported as a more accurate method for identifying infants with motor delays.
Abstract:
The purpose of this study was to evaluate the intra-individual stability of gross motor scores obtained by normally developing full-term infants on the Alberta Infant Motor Scale (AIMS). The gross motor skills of 47 infants were assessed monthly in their homes by pairs of physical therapists. Infants were followed from two weeks of age until they achieved independent walking. A developmental pediatrician assessed each infant at 18 months of age, and classified the infant's gross motor skills as normal, suspicious or abnormal. Only the data of infants receiving a normal classification at 18 months were included in the analyses (n = 45). Individual infants' percentile ranks varied considerably from month to month, with no systematic pattern of change noted across infants. As a group, the mean percentile range over 13 assessments was 66.78 (S.D. 13.47). Fourteen infants (31.1%) received a score below the 10th percentile on at least one occasion. The results suggest that normally developing infants are not stable in the rate of emergence of gross motor skills. This instability has implications for infant screening programs, and supports the premise of serial assessments to identify accurately those infants with a motor delay.
