The Centipede's Dilemma

The poem

The poem, a short rhyme illustrating a solvitur ambulando in reverse, is usually attributed to Katherine Craster (1841–1874) in Pinafore Poems, 1871. By 1881 it had begun appearing in journals such as The Spectator and The Living Age. The poem later appeared in an article by British zoologist E. Ray Lankester, published in the scientific journal Nature on May 23, 1889, which discussed the work of the photographer Eadweard Muybridge in capturing the motion of animals: "For my own part," wrote Lankester, "I should greatly like to apply Mr. Muybridge's cameras, or a similar set of batteries, to the investigation of a phenomenon more puzzling even than that of 'the galloping horse'. I allude to the problem of 'the running centipede'". Lankester finished the article on a fanciful note by imagining the "disastrous results in the way of perplexity" that could result from such an investigation, quoting the poem and mentioning that the author was unknown to him or to the friend who sent it to him. It has since been variously attributed to specific authors but without convincing evidence, and often appears under the title "The Centipede's Dilemma".

The version in the article is as follows:

A centipede was happy – quite!Until a toad in funSaid, "Pray, which leg moves after which?"This raised her doubts to such a pitch,She fell exhausted in the ditchNot knowing how to run.

Another version of the Centipede's Dilemma:

A centipede was happy – quite!Until a toad in funSaid, "Pray, which leg comes after which?"Which threw her mind in such a pitch,She laid bewildered in the ditchConsidering how to run.

Modern versions of the poem often recast it in verse as a fable of a spider (or other protagonist) who found a clever way to avoid being eaten.

Another rhyme goes:

A spider met a centipede while hurrying down the street,"How do you move at such a speed, with all so many feet?""I do not have to contemplate to keep them all in line,But if I start to concentrate they're tangled all the time!"

In psychology and philosophy

The psychologist George Humphrey referred to the tale in his 1923 book The Story of Man's Mind: "No man skilled at a trade needs to put his constant attention on the routine work", he wrote. "If he does, the job is apt to be spoiled". He went on to recount the centipede's story, commenting, "This is a most psychological rhyme. It contains a profound truth which is illustrated daily in the lives of all of us, for exactly the same thing happens if we pay conscious attention to any well-formed habit, such as walking". Thus, the eponymous "Humphrey's law" states that once performance of a task has become automatized, conscious thought about the task, while performing it, impairs performance. Whereas habit diminishes and then eliminates the attention required for routine tasks, this automaticity is disrupted by attention to a normally unconscious competence.

The philosopher Karl Popper referred to the centipede effect in his book Knowledge and the Body-Mind Problem: In Defence of Interaction: "if we have learnt certain movements so that they have sunk below the level of conscious control, then if we try to follow them consciously we very often interfere with them so badly that we stop them". He gives the example of the violinist Adolf Busch who was asked by fellow-violinist Bronisław Huberman how he played a certain passage of Beethoven's violin concerto. Busch told Huberman that it was quite simple—and then found that he could no longer play the passage.

The psychiatric psychoanalyst Theo L. Dorpat compares questions and interventions irrelevant to the patient's current thought process during psychotherapy in his book Gaslighting to "the story of the centipede who became disorganized and unable to walk after he was asked, 'What's wrong with your 34th left foot?'."