Moreover, the principle of sexual selection implies that, in addition to regulating bodily functions, the nervous system indirectly influences the progressive development of bodily and mental structures such as ornamental appendages; cognitive skills like musical ability; and characteristics such as courage and perseverance. Peacocks have evolved to have long, colorful feathers simply because peahens have evolved to find them attractive.
此外，性选择的原理意味着，除了调节生体机能，神经系统还间接地影响身体和精神的结构结构（比如装饰性特征）、认知技能（比如音乐天赋）和性格（比如勇气和毅力）的进步发展。雄孔雀进化出了色彩斑斓的长尾，唯一原因是雌孔雀进化出了以此判断吸引力的功能。