Spatial Extent Estimator
Sub Trajectory: Numerosity Estimation

Extends sets and number categories to include “small numbers,” which are usually subitized, not estimated, “middle-size numbers” (e.g., 10–20) and “large numbers.” The arrangement of the to-be-estimated set affects the difficulty.


You may see this:

Linked Image to Sign In/Sign Up page

Other Examples:

  • Shown 9 objects spread out randomly for 1 second and asked, "How many?," the child guesses, "14."
  • Shown 25, the child guesses “40."

Help your student become a(n) Spatial Extent Estimator

Activities ask children to estimate the number of objects in a set, with scaffolding that first asks them if it's a small number (e.g., 4 or 6), middle-sized (e.g., in the teens) or large (beyond 20).

Special Thanks To

Institute of Education Sciences
The research reported here was supported by the Institute of Education Sciences, U.S. Department of Education, through grant numbers R305K050157, R305A120813, R305A110188, and R305A150243. to the University of Denver. The opinions expressed are those of the authors and do not represent views of the Institute or the U.S. Department of Education.