Table 1.

The output from the stepwise regression analysis employed to examine the effect of DBH 444 G/A and COMT Val¹⁵⁸Met genotype status and their interactions (independent factors) on different aspects of attention (dependent variables). Significant results are reported in bold.

Attention index	Factors	Coefficients	Standard Errors	p-values
d’ change (‘sustained attention’)	COMT DBH COMT X DBH	0.0236 0.1164 0.0104	0.0448 0.0454 0.0196	0.59 0.01* 0.59
RT-SD (‘performance stability’)	COMT DBH COMT X DBH	4.4739 5.2376 1.8233	3.2910 3.3418 1.0834	0.17 0.11 0.09
False-alarms rate (‘response inhibition’)	COMT DBH COMT X DBH	0.0016 0.0003 0.0009	0.0039 0.0040 0.0013	0.68 0.93 0.47
Visual short-term memory capacity	COMT DBH COMT X DBH	− 0.1104  − 0.0612  − 0.0377	0.0749 0.0767 0.0247	0.14 0.42 0.13
Perceptual threshold	COMT DBH COMT X DBH	2.7251  − 1.1731  − 0.3907	0.9936 1.0100 0.4684	0.007* 0.25 0.41
Processing speed	COMT DBH COMT X DBH	− 1.0397  − 2.3814  − 0.8914	2.0286 2.0559 0.6663	0.60 0.24 0.18
Spatial bias	COMT DBH COMT X DBH	0.0033  − 0.0015 0.0018	0.0086 0.0088 0.0028	0.70 0.86 0.51
Top-down selectivity index	COMT DBH COMT X DBH	0.0600  − 0.0016  − 0.0074	0.0341 0.0349 0.0161	0.08 0.96 0.64