Very interesting wiki article: http://en.wikipedia.org/wiki/Kruithof_curve
Knowing this, I find it very surprising that cool-white temperature LED's are popular at all. Everyone should be competing to buy the warm colors.
QUOTE: "due to the Purkinje effect: the wavelength of light for which the eye is most sensitive depends on the luminance"
QUOTE: "at typical home illuminance levels (75 lux), pleasing color temperatures are between 2400 and 2700 K"