Appendix A.

Factor loadings on the first principal component of the items of mathematical self-evaluation.

Item	Age 9	Age 12
SPA – number	0.786	0.816
SPA – arithmetic	0.803	0.838
SPA – multiplying	0.776	0.815
Liking – number	0.82	0.822
Liking – arithmetic	0.849	0.855
Liking – multiplying	0.812	0.821

Note. SPA – number: self-perceived ability of solving numbers; SPA – arithmetic: self –perceived ability of mental arithmetic; SPA – multiplying: self-perceived ability of multiplying and dividing; liking – number: liking of solving numbers; liking – arithmetic: liking of mental arithmetic; liking – multiplying: liking of multiplying and dividing.