Table 2.

Pearson correlation between the paired people in each subject group on the behavioral performance measures

	MZ	DZ	SIB	UNR
Proportion correct	0.44 (P < 0.001)a	0.14 (P = 0.13)b	0.36 (P < 0.001)c	−0.32 (P = 0.004)a,b,c
d′	0.43 (P < 0.001)a	0.25 (P = 0.03)b	0.32 (P < 0.001)c	−0.38 (P = 0.002)a,b,c
Median RT	0.34 (P < 0.001)a	0.17 (P = 0.062)	0.11 (P = 0.388)	−0.07 (P = 0.4)a

P values (in parentheses) were calculated with hc4wtest, a robust regression test for R² different than zero (Wilcox 2017), and uncorrected for multiple comparisons. Scatterplots and regression lines are in Supplementary Material, Section S1.2. Significantly different pairwise correlations within each row (i.e., on each measure) are indicated by shared superscripts, with P < 0.0083 (Bonferroni correction of 0.05 for 6 comparisons) as the significance threshold. All pairwise comparison P values are listed in Supplementary Material, Section S1.2 and were calculated by twohc4cor (Wilcox 2017). The astute reader will note negative correlations among the UNR pairs, which unexpectedly reached statistical significance for some of the measures. We believe that the observed negative correlations reflect a sampling anomaly, as a larger set of unrelated pairings was quite close to the expected zero correlation (Supplementary Material, Section S1.5). Regardless, this does not seriously influence our key analyses or interpretations, which center on neural pattern similarity relationships among related pairs.