A recent study shows that ninja was a group of engineers who had abundant knowledge of animals and plants, and chemistry as well as a group of intelligence agents who had great physical ability and were strictly disciplined.
近年の研究では、身体能力に優れ、厳しい規律に律された諜報集団という面の他に、優れた動植物の知識や化学の知識を持つ技術者集団としての一面も持つことが判っている。