Figure 1. Leadership ratio according to the condition for groups of 2 individuals.

Condition 1 (a.): needs are equal (a₁ = a₂ = b₁ = b₂). Condition 2(a.): needs of each individual are different but their sums are equal between individuals (a₁>a₂; b₁>b₂; a₁+a₂ = b₁+b₂). For these two conditions, the leadership is equally distributed between individuals (Kolmogorov-Smirnov test, P>0.972). Condition 3(b., c.): the sum of needs for one individual is superior to the one of individual. For Condition 3, the ratio (a₁+a₂)/(b₁+b₂) ranged from 1 (Group 1) to 1.45 (Group 10). For this condition, one individual becomes the leader when its needs are superior to the ones of its conspecifics. Fig. 1c represents the difference of leadership according to the relative difference of needs between A and B.