Even Gardner himself reaches no firm conclusions. In 1999 he included natural observation: for example, people who share Darwin's love for investigating nature or who can distinguish different kinds of plants and animals possess this kind of intelligence.
連嘉納自己都不敢下結論，一九九九年他加入了自然觀察的智能，例如像達爾文這種喜歡探索大自然、可以分辨不同種類動植物的人，就具有這樣的智能。