What is the Gesell Developmental Observation?

What is the GDO-R?

The Gesell Developmental Observation-Revised (GDO-R) is part of a comprehensive multi-dimensional assessment system that assists educators, and other professionals in understanding characteristics of child behavior in relation to typical growth patterns between 2½ to 9 years of age. 

Uniquely, Gesell expert assessors are available to offer ongoing technical assistance not available with most other assessment systems.

The GDO-R uses direct observation to evaluate a child’s cognitive, language, motor and social-emotional responses in five strands (domains): Developmental, Letter/Numbers, Language/Comprehension, Visual/Spatial and Social-Emotional/Adaptive.

The GDO-R is supported by current psychometric data published in the GDO-R Technical Report and meets the government mandates for initial screening of a child 3-6 years.

The components of the GDO-R include:


The Results of the GDO-R 

A child’s performance on each strand (4 domains) corresponds to a strand Performance Level Rating, an overall Performance Level Rating and a Developmental Age.

Developmental Age is an identification in years and half-years that best describes a child’s behavior and performance on a developmental scale compared to most children. Developmental Age may be equal to, older than or younger than the child’s chronological age. 

The results also allow for the assessment of an Overall Performance Level rating of Age Appropriate, Emerging or Concern. This information can be used as a guide to individualize instruction for a child, customize curricula for a group and identify when additional diagnostic evaluation may be of use.


Mandatory Training to Become a GDO-R Examiner

Gesell requires specialized training, through online or hybrid GDO-R Workshops. Public workshops are open to all and scheduled one year in advance; many will sell out so reserve your spot early! You may also choose to host a private workshop for your staff. 

Participants completing GDO-R workshops become qualified examiners with the skills to administer the GDO-R tasks and prepared to determine a child’s Developmental Age and Performance Level Ratings.

Examiners are required to return for re-training every 5 years to maintain their qualified examiner status. All examiners are encouraged to continue on the ladder of examiner training, pursue advanced training and apply to our National Lecture Staff.

When using the GDO-R, Gesell recommends using best practices during the assessment of very young children.

Gesell does not set policy or provide recommendations surrounding issues of retention, placement, or readiness “scores” in association with the GDO-R.


"The Gesell seminar was very interesting and informative with many useful tools and supplies provided for step by step instructions throughout the material.  The hands-on exercises and student demonstrations were very helpful." - Phyllis from Dallas