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 the Hutt), there’s far less variation in her vocalizations than there is in my roommate’s. She can convey urgent hunger (and often does), a desire for attention, a sense of contentment, and a few other basic pieces of information, but even that variation is expressed by only a very narrow range of vocalizations. My roommate, on the other hand, often surprises me, both with what kind of information he conveys and how he conveys it. Intuitively, my roommate’s vocalizations are the more complex.

We can also think of “surprise” as tracking something about how much I miss if I fail to hear part of a message. In messages that are more surprising (in this sense), missing just a small amount of data can make the message very difficult to interpret, as anyone who has ever said expressed incredulity with “What?!” can attest; when a message is received and interpreted as being highly surprising, we understand that just having misheard a word or two could have given us the wrong impression, and request verification. Missing just two or three words in a sentence uttered by my roommate, for instance, can render the sentence unintelligible, and the margin for error becomes more and more narrow as the information he’s conveying becomes less familiar. If he’s telling me about some complicated piece of scholarly work, I can afford to miss very little information without risking failing to understand the message entirely. On the other hand, if he’s asking me what I’d like to order for dinner and then listing a few options, I can miss quite a bit and still be confident that I’ve understood the overall gist of the message. My cat’s communications, which are less surprising even than the most banal conversation I can have with my roommate, are very easily recoverable from even high degrees of data loss; if I fail to hear the first four “meows,” there’s likely to be a fifth and sixth, just to make sure I got the point. Surprising messages are thus harder to compress in the sense described in Chapter One, as the 62