Table 1.

Behavioral results for the arithmetic tasks

Task	Npresented trials			RT			ACC
	F 1,18	p	${\eta }_p^2$	F 1,17	p	${\eta }_p^2$	F 1,17	p	${\eta }_p^2$
Addition
Grade	2.93	.104	.140	1.49	.283	.081	3.98	.062	.190
Complexity	166.33	< .001	.902	92.72	< .001	.845	15.63	.001	.479
Grade × complexity	0.08	.783	.004	1.19	.291	.065	7.75	.013	.313
Subtraction
Grade	1.61	.220	.082	1.43	.263	.073	7.32	.015	.301
Complexity	299.87	< .001	.943	178.29	< .001	.913	7.20	.016	.297
Grade × complexity	6.61	.019	.269	0.39	.539	.023	0.03	.877	.001
Multiplication
Grade	0.00	.984	.000	0.73	.405	.041	3.24	.090	.160
Complexity	191.66	< .001	.914	101.87	< .001	.857	55.25	< .001	.765
Grade × complexity	1.27	.275	.066	0.24	.634	.014	0.16	.698	.009
Division
Grade	0.03	.860	.002	0.69	.418	.039	1.15	.298	.063
Complexity	150.03	< .001	.893	24.79	< .001	.593	67.90	< .001	.800
Grade × complexity	0.47	.500	.026	0.58	.458	.033	0.66	.428	.037

Significant effects are shown in italics.