Time flies like an arrow; fruit flies like a banana. Or do they?

In my postprandial presentation at Churchill College I stressed the importance of natural language in Artificial Intelligence – and the more I think of this, the more important I believe natural language will be in communicating with computers. I am probably a weak adopter of Linguistic Realilty (http://en.wikipedia.org/wiki/Linguistic_relativity ) – I recently reread 1984 and its plausible ending of dumbing down human thought by imposed restricted language. Our current attempts to communicate chemistry to and from machines will certainly be very limited and even less expressive than Newspeak.
But any expressive language is ambiguous. The English language is particularly prone to ambiguity since most of its words are not inflected and there is no lexical clue in many cases the as to the part of speech. Many common verbs and nouns share the same or similar lexical forms, sometimes being homophones or homonyms and sometimes being capable of use in either nounal or verbal forms.
A particularly amusing example of this (http://en.wikipedia.org/wiki/Time_flies_like_an_arrow;_fruit_flies_like_a_banana ) is frequently quoted in introductions to linguistics and I used it to show that whatever claims I made of computers understanding chemistry there will be many cases where the spoken or written words will be ambiguous to humans. I will use this to introduce part of speech tagging (POS).

NN Time VBZ flies PRP like DT an NN arrow;

NN fruit NN flies VB like DT a NN banana

Here NN=noun; VB=verb; PRP=preposition; DT=determiner (article); it should be noted that there are many schemes of POS-tagging and we generally use the Brown tagger. The main point of this article is to try to uncover the source of these quotations, but first I will comment on how the tagging takes place.
The Brown tagger attempts to put a unique tag on each token (a token is normally a white space separated word). Words such as “the” and “a” are normally unambiguous and in this case have been tagged as DT. But the words “like” and “files” are homonyms (http://en.wikipedia.org/wiki/Homonym). Taken in isolation it is impossible to give them a POS tag. Because of this full natural language parsing can be extremely expensive computationally and often results in a large number of different possible parses. These can be collected into a tree bank and different interpretations can be selected on the basis of probability and usage. Here the problem arises in that we have to understand the meaning of “time” and “fruit fly”. If we did not know that there was such things as fruit flies the second sentence might be parsed in the same way as the first. Similarly if we believe there are creatures called time flies which eat arrows then the first sentence can be interpreted with a similar meaning to the second.
I believe I first heard this pair of sentences in about 1969 at the University of Stirling where Christopher Longuet-Higgins gave a public lecture on artificial intelligence. However when I wished to cite it in my presentation I turned to the net and found it was apparently a quotation from Groucho Marx and labelled it as such. After the presentation one of my colleagues, Ray Abrahams (http://www.chu.cam.ac.uk/~RGA1000/), thought it might have come from Noam Chomsky. We turned to the net and found that neither of us was completely sure. Today Ray has written an email with some extra information which I reproduce in full in case it helps to clear up the origin.
Ray writes:
I suspect we are both wrong about the ‘quotation’. It does not appear to be Chomsky’s (though it seems to have emerged under the influence of his work) and there is a statement on Wiki[pedia] as follows:

“Time flies like an arrow. Fruit flies like a banana ”

No known citation to Marx. First appears unattributed in mid-1960s logic/computing texts as an example of the difficulty of machine parsing of ambiguous statements. Google Books. The Yale Book of Quotations dates the attribution to Marx to a 9 July 1982 net.jokes post on Usenet”. (http://en.wikiquote.org/wiki/Groucho_Marx )

The main 60s text is […] by Anthony Oettinger on ‘The Uses of Computers in Science’. It was published in a special issue of Scientific American in 1966 (Vol 215 No 3 p 161-72) on computers. […] It is also in a later bound volume of papers from Scientific American

Oettinger seems to have worked with Susumo Kuno on this and other language problems (above 166-7), and it seems to be their results, offering several different computer readings of the line, that are quoted by Steven Pinker in the Language Instinct (p.209), though he mentions neither of them.

Google books under ‘fruit flies like a banana’ gives several texts where Oettinger’s paper is included or quoted.

I came across Oettinger’s stuff originally through our retired fellow, John Barnes who cited it in an article called Time Flies Like an Arrow in the journal Man, New Series, Vol.6, No.4 p.537-52. There is a copy of this in the college library and it is on Jstor. It contains a nice verse apparently written by one Edison B. Schroeder. I could not find the text of it where Barnes references it (i.e. in the same 1966 SA volume).

Now, thin fruit flies like thunderstorms

And thin farm boys like farm girls narrow;

And tax firm men like fat tax forms –

But time flies like an arrow.

When tax forms tax all firm men’s souls,

while farm girls slim their boyfriends’ flanks;

That’s when the murd’rous thunder rolls –

and thins the fruit flies ranks.

Like tossed bananas in the skies,

The thin fruit flies like common yarrow;

Then’s the time to time the time flies –

Like the time flies like an arrow.

[PMR] My simplistic citing is an example of how attributions can multiply without formal checking; however Wikipedia always progresses forward (i.e. improvement) and will gradually become the best source. So perhaps this episode may help the maintainers of this page.
And many thanks to Ray.