「さて、知的行動をとる人間もそうだが、本能的に行動する動物が、ときどき彼らなりの妄想や錯覚にとらわれて、ものごとを見誤り、まちがった刺激によって自分たちに不利な行動に駆り立てられることは、よく知られた事実である。群れや家族のものたちが、仲間の一匹の苦悶の叫びを聞いたり、血の流れる傷口を見たり、そのにおいを嗅いだりして、または仲間がまるで手ごわい敵の手にかかったかのように、地上であるいは木や岩の割れ目で狂ったようにもがいているのを見て、突如恐ろしい怒りにかられたとき、彼らは仲間を殺すためで（411頁）はなく、救うためにとびかかっていくのである。
救助本能［…］の効果は、その動物のなかにかき立てられた、眼に見え触れることのできる敵、あるいは目に見えない敵に対する怒りにまったく依存するのである。だとすれば、動物たちがときたま遭遇するだけの、めったにない事故のおりには用をなさないことはあきらかで、そのようなときには、彼らは敵に捕まり倒されたときとまったく同じような行動をとる。彼らの錯覚は、われわれのなかに強烈な期待から生まれる幻想に似た感情の産物である。この錯覚のために、多くの人々が友人や仲間を自分が待ち受ける敵と見誤り、そのあやまった怒りから友だちを殺してきた。（412頁）
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ある象が落とし穴からはい出たあと、仲間がそこから逃げ出すのを助けたのを覚えているダーウィンにとっては、野生の象が苦しんでいる仲間を襲うことは驚くべきことだと思われた。しかし、系統分類学上は高等であろうと下等であろうと、群棲社会を構成してたがいに助け合う本能をもつまさにその動物が、ときとして不幸な仲間を攻撃するのであって、そのような攻撃は救助本能の大きな誤りでしかない。」（ハドスン『ラプラタの博物学者』413頁）
Now, it is a pretty familiar fact that animals acting instinctively, as well as men acting intelligently, have at times their delusions and their illusions, and see things falsely, and are moved to action by a false stimulus to their own disadvantage. When the individuals of a herd or family are excited to a sudden deadly rage by the distressed cries of one of their fellows, or by the sight of its bleeding wounds and the smell of its blood, or when they see it frantically struggling on the ground, or in the cleft of a tree or rock, as if in the clutches of a powerful enemy, they do not turn on it to kill but to rescue it.
In whatever way the rescuing instinct may have risen, whether simply through natural selection or, as is more probable, through an intelligent habit becoming fixed and hereditary, its effectiveness depends altogether on the emotion of overmastering rage excited in the animal--rage against a tangible visible enemy, or invisible, and excited by the cries or struggles of a suffering companion; clearly, then, it could not provide against the occasional rare accidents that animals meet with, which causes them to act precisely in the way they do when seized or struck down by an enemy. An illusion is the result of the emotion similar to the illusion produced by vivid expectation in ourselves, which has caused many a man to see in a friend and companion the adversary he looked to see, and to slay him in his false-seeing anger.
An illusion just as great, leading to action equally violent, but ludicrous rather than painful to witness, may be seen in dogs, when encouraged by a man to the attack, and made by his cries and gestures to expect that some animal they are accustomed to hunt is about to be unearthed or overtaken; and if, when they are in this disposition, he cunningly exhibits and sets them on a dummy, made perhaps of old rags and leather and stuffed with straw, they will seize, worry, and tear it to pieces with the greatest fury, and without the faintest suspicion of its true character.
That wild elephants will attack a distressed fellow seemed astonishing to Darwin, when he remembered the case of an elephant after escaping from a pit helping its fellow to escape also. But it is precisely the animals, high or low in the organic scale, that are social, and possess the instinct of helping each other, that will on occasions attack a fellow in misfortune--such an attack being no more than a blunder of the helping instinct.
