Table 1. Subjects data and illumination conditions of experimental sessions.

For illumination we used either fluorescent lamps mounted at the room ceiling (Philips Master Tl-D 58W/840, 4000K cold white) or setup halogen lamps (Philips Brilliantline 20W 12V 36D 4000K). Luminance was measured by luminance meter LS-100 (Minolta) with close-up lens No 135 aiming at the ridge of the monkey nose (settings: calibration preset; measuring mode abs.; response slow; measurement distance ≈ 55 cm).

Animal	Sessions	Age, full years	Weight, kg	Illumination	Luminance, cd/m2
Sun	1, 2	16	12.0	fluorescent	87.5
Fla	3, 4	8	14.4	fluorescent+daylight	12.9
Mag	5, 6, 9, 10	11	10.6	fluorescent+daylight	12.8
	7	12	10.1	halogen+daylight	4.0
Lin	8	10	9.6	fluorescent+daylight	12.7