programming-for-dummies

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Problem Solving
ELIZA doesn’t actually understand the meaning of words. Instead, ELIZA just
knows how to arrange words in their proper position to mimic an intelligent
conversation. When ELIZA spots a word, such as sister, brother, or father, it
immediately searches its database for a list of canned replies related to
asking the user questions about his or her family.
By combining both canned phrases and parroted replies, ELIZA succeeded in
mimicking an ordinary conversation. Although Joseph Weizenbaum originally
created ELIZA to research natural language processing, he was astounded at
how readily people accepted ELIZA and treated it as an intelligent computer
even though they knew how it was programmed. When Weizenbaum found his
secretary typing her problems into ELIZA and requested that he leave so she
could have privacy, he became an advocate against artificial intelligence.
One common application of natural language processing can be seen in the
help system of many programs. If you type How do I print a document, the
help system for your word processor might display a list of topics for printing
files. The computer didn’t actually understand the sentence. Instead, the
computer, like ELIZA, just scanned the sentence, looking for keywords that it
could recognize and then responded based on the keywords that it found.
To poke fun at ELIZA, Kenneth Colby, a psychiatrist at Stanford University,
wrote a similar program dubbed PARRY. Whereas ELIZA mimicked a therapist,
PARRY mimicked a paranoid, schizophrenic patient. Computer scientists often
connect ELIZA with PARRY to see what amusing conversation these two
programs could create from each other.
Speech recognition
Similar to natural language processing is speech recognition. Like NLP, speech
recognition must identify a word and deduce its meaning. But unlike NLP,
speech recognition has the added burden of trying to do all this in real-time.
The moment someone says a word, the speech recognition computer must
quickly understand that word because the speaker won’t likely pause for long
before saying the next word.
The simplest form of speech recognition involves choosing from a limited
selection of distinctly different sounding words. Many voicemail systems offer
this feature by asking a question such as, “Do you want to leave a message?” At
this point, the speech recognition computer listens for any sound that resembles
either Yes or No. Because the speech recognition computer has such a limited
selection to choose from, its accuracy rate can be almost perfect.
A second way to understand speech is to force users to train the computer
first by saying a limited selection of words. The computer then stores these
spoken sounds in a database so the next time the user talks, the speech recognition
matches every spoken word with the closest match in its database.