A growing body of evidence reveals the need for research on, and
consideration for, children’s and students’ own—self-guided—spontaneous
use of mathematical reasoning and knowledge in action. Spontaneous
focusing on numerosity (SFON) and quantitative relations (SFOR) have
been implicated as key components of mathematical development. In this
chapter, we review existing research on SFON and SFOR tendencies in the
broader context of the development of mathematical skills and knowledge
and examine how the state-of-the-art evidence on SFON and SFOR is
relevant for the field of mathematics education. We discuss individual
differences in SFON and SFOR, associations between spontaneous focus on
mathematical features and mathematics achievement, the contributions of
situational contexts that implicitly prompt attention to number, and
ways to increase children’s focus on number regardless of their baseline
level tendencies. We conclude that children’s and students’ tendencies
to focus on number and quantitative relations–spontaneous or
otherwise–are key components of mathematical development and education.