Because of the time delay and disproportion message function,limit cyclesexist in the third model.With the same reason, it makes the third model the mostsuitable one to re?ect the real world.

• 模型三最为复杂；它既带有时滞；信号函数也是非对称的；它的动力学性质最为复杂:出现了极限环.；也因为同样的原因；它最能反映真实的情况