Fig. 6. Two nocturnal geckos of the species Tarentola chezaliae learnt to take a cricket from forceps decorated with a pattern made from blue squares (right). The forceps decorated with a grey pattern (left) always held a salted cricket, which geckos always refused. Both geckos predominantly chose blue in all tests, independent of the overall intensity of the grey pattern (represented by the different shades of the grey patterns on the abscissa). (Data from Roth and Kelber, 2004.)