The Talmud (Megilah 3A) imparts the following wisdom (comments in parenthes
is are my own):
"Ravina said: ...If someone becomes frightened, even though he does not see (the source of his fright), his guardian angel does see it. (I.e. A person will become subconsciously aware of a spiritual danger although he cannot consciously detect it.) What can one do to rectify the situation? One should recite the Shema. (The recitation of the Shema has the ability to ward off spiritual dangers.) But if one is standing in a filthy place (not suitable for the recitation of the holy words of the Shema), one should leap four cubits from one's place. If one cannot [leap from one's place], one should say this: 'The goat at the slaughterhouse is fatter than me' (to ward off the spiritual attacker by directing it to a more tempting target)."
Rabbi Yoseph Chayim of Baghdad (a.k.a. Ben Ish Chay), in his classic commentary to the aggadic portions of the Talmud, Ben Yehoyada, explains:
"The reason [the sages of the Talmud] said one should leap, and did not say one should 'distance oneself' four cubits, is because they devised a wise [strategy] to save one from the demons (i.e. the spiritual predators) through leaping from one's place. It is known what our master, the Arizal, taught, that the entire desire of the evil inclination is to make itself appear similar to that which is holy, like a monkey vis-a-vis a man, that is, that the nature of a monkey is that it acts as the man who is before it. Therefore, the demons, who are rooted in the evil inclination, also have this nature of the monkey, to performs acts like the acts of men, in order to make themselves similar to them. Therefore, it seems that the guardian angel of this person who becomes frightened sees that there are demons standing there next to him, and if he would distance himself from that place via walking, [the demons] too would walk with him, so what good would distancing himself do? Therefore they gave him the advice to leap four cubits, for then his leaping would be great and strong according to his ability, for he would be compelled to leap with all his strength, and the demons, whose way is to mimic the action that the man performs before them, like the way of the monkey, would certainly also perform a great leaping with all their strength after seeing that this person strengthened himself to leap with all his might. Then the leaping of the demon, commensurate with its level of strength, would be to a very distant place, possibly several hours distant, for in accordance with the strength of the demon who leaps with all its strength, certainly its leaping will be a very great measure, and once it is uprooted (from its attachment to the person), it is uprooted (and will no longer follow the person). The result is that this man is separate and distant from them a great and awesome measure."
And here comes the kicker, as the Ben Yehoyada continues (emphasis added):
"And I heard people telling that a certain seaman did such a stratagem to monkeys that wore the hats that were spread out on the shore before the boat, and through such a stratagem he took all the hats that the monkeys had taken, since the nature of monkeys is to do that which the man before them does, for they desire to be similar to men."
And while Caps for Sale was published in 1938, the earliest edition of Ben Yehoyada of which I am aware was printed in 1904.
