Social supporting rates among stratified groups show some kinds of differentiated distributional pattern. I introduce a cognitive model to explain these patterns. The focused process is that the stratified social structure restricts the cognitive bases of people who are providing support, which in turn results in the differentiated supporting rates among groups. We assume that people have the cognitive selectivity in providing support and seventeen selectivity types are determined by the cognitive condition. Among them, two types never produce any differentiated pattern, and seven types unconditionally generate the proportionally differentiated pattern (the upper the group, the higher the supporting rate). Other eight types are dependent on the shapes of the stratification structures. Examining two typical shapes, “pyramid” and “diamond”, I found that ; 1) both shapes allow the inversely proportional pattern and the convex curve (“D-pattern” : middle groups have higher supporting rates), but 2) the concave curve (“K-pattern” : middle groups have lower supporting rates) appears only with “diamond” being conditioned by the out-group oriented selectivity type (out-group demands are prior to others).