Hanggi EB, Ingersoll JF, Waggoner TL. 2007. Color vision in horses (Equus caballus): deficiencies identified using a pseudoisochromatic plate test. J Comp Psychol. 2007 Feb;121(1):65-72.

• 下面的研究表明，马所能辨别的颜色与人类红绿色盲所看到的颜色一样。