“I need to follow the numbers”—developing and validating a more comprehensive measure of spontaneous focusing on numerical order

Abstract Spontaneous focusing on numerical order (SFONO) has been suggested as a relevant construct for the development of ordinality knowledge, as children who more often notice numerical order in everyday situations tend to exhibit better ordinality knowledge. However, earlier SFONO measures risked conflating SFONO with the skills needed in them and focused only on numerical sequences with small, consecutive numbers. This study addressed this gap by developing a revised SFONO measure. The construct validity of the measure was examined through three approaches: (1) assessing its ability to replicate individual differences in SFONO, (2) evaluating the influence of various task contexts and numerical sequences on SFONO scores, and (3) confirming its divergent validity from the requisite skills needed to perform the tasks. Fifty-one children ( M age = 5.75 years) completed four SFONO tasks featuring varied contexts and a wider range of numerical sequences. Results indicated that consistent individual differences in SFONO could be observed across diverse situations, providing evidence for the construct validity of its measurement. In addition, the SFONO measure showed divergent validity from the necessary skills, supporting the interpretation that SFONO reflects a distinct construct. Interestingly, SFONO responses appeared more affected by the numerical sequences used in the task than by the task context. Put together, the study highlights the need to carefully consider a wider range of task features when attempting to measure spontaneous mathematical focusing tendencies.