[Differentiation of the intensity of photic stimuli in chickens]

Differentiation of photic stimuli brightness with different brightness ratios was studied in hens by means of food-procuring conditioned reflexes in situation of alternative choice of positive conditioned signal. It has been found that the speed of formation, stability of differentiations and the degree of discrimination of signals by their brightness is in a significant correlation with the ratio of stimuli intensity. Mean speed of elaboration of low (1 : 6.3; 1 : 5.4; 1 : 3.7; 1 : 3.5 and 1 : 3) and medium (1 : 2.75; 1 : 2.55 and 1 : 2) complexity differentiations made 61.62 +/- 12.23 presentations of conditioned signals, and a mean value of differentiation degree made 87.02 +/- 1.35% of adequate choice reactions. Complex differentiations of photic stimuli (1 : 1.75; 1 : 1.5 and 1 : 1.2) were elaborated with difficulty, and the differentiation degree of these signals averaged 53.42 +/- 4.12% of adequate reactions. Differentiation of photic stimuli with 1 : 2 intensity ratio was the limit of brightness discrimination.