Table 1. Participant characteristics and working memory performance.

	Mean	SD	Range
Age tp1	6.2	1.1	4.2–9.3
Age tp2	7.8	1.1	5.8–11.0
Interval years	1.6	0.1	1.3–2.2
Spatial Span Backwards tp1 a	3.3	1.4	0–7
Spatial Span Backwards tp2 b	4.4	1.0	2–7
Digit Span Backwards tp1c	2.7	1.1	0–5
Digit Span Backwards tp2d	3.4	0.9	2–6

Participant’s cognitive scores at time point 1 (tp1) and time point 2 (tp2). Number of participants;

^a n = 148,

^b n = 147,

^c n = 145,

^d n = 146.