Journal of Circadian Rhythms

Table 2 Color dimensions (mean ± SD) for subjects with blue and brown irises.

From: Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color

Iris Color	Blue Irises	Brown Irises	Correlation with
Dimension	n = 7	n = 6	phase shift (n = 13)^b
Blue^a	125.5 ± 9.6**	42.7 ± 9.3	r = .40, p = 0.17
Green^a	143.0 ± 5.2**	93.3 ± 18.0	r = .31, p = 0.31
Red^a	130.1 ± 2.2	123.0 ± 17.3	r = .14, p = 0.64
Lightness	57.9 ± 1.4*	43.0 ± 7.2	r = .29, p = 0.33

* p < 0.01; ** p < 0.001, t-test comparing subjects with blue vs brown irises
^a Measured from 3 dimensions of the RGB color system.
^b Positive correlations indicate that subjects with darker irises had larger phase delays.

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